There has been a serious debate going on this subject for quite a few years all over the world. People say that all the popular religions indicate the end of the world on this day.
They even say that Nostradamus had given a similar prediction. They also claim the Mayan’s calendar ends on this day.
They give so many reasons for the end of the world. It could be the result of the third world war. It could be the result of drastic changes in the solar system. It could also be the result of huge natural calamities.
It is also said that the earth’s magnetic field is changing to a great extent and so on and on. They also say that there is a serious threat to earth by some comets and asteroids that are fast approaching towards the earth.
The earth has been surviving for millions and millions of years. It had experienced so many disasters in the past but never failed in its survival. Of course, there have been many earth faults and notable changes in the global phenomenon.
Friday, October 30, 2009
Will Earth Die a “Natural” Death?
According to recent research, the devastating, although not very urgent, news on the long-term status of planet Earth is now in. Clara Moskowitz, a staff writer for Space.com, recently reported that new calculations suggest the Earth will be sucked into the Sun and burned to a crisp in 7.6 billion years (2008). The new “findings” come from work done by Robert Smith, former professor at the University of Sussex, in association with astronomer Klaus-Peter Schroeder.
Smith warned that while 7.6 billion years might seem like too far in the distant future to cause concern, things would get deadly several billions of years before that. He proposed that in about one billion years the Earth will be so close to the Sun that there will be “no atmosphere, no water and a surface temperature of hundreds of degrees, way above the boiling point of water” (as quoted in Moskowitz).
The reason for Earth’s expected demise is a slowing down of the Earth’s orbit caused by gravitational forces from the Sun as well as forces from gas that the Sun expels. As bleak as Earth’s eventual destruction sounds, Smith is still upbeat. Moskowitz reported: “Some scientists have proposed a scheme for down the road to use the gravity of a passing asteroid to budge Earth out of the way of the sun toward cooler territory, assuming there is life around at the time that is intelligent enough to engineer this solution” (2008). Concerning this bizarre solution, Smith commented that it sounds like science fiction, but “[i]f it is done right, that would just keep the Earth moving fast enough to keep it out of harm’s way. Maybe life could go on for as much as 7 billion years” (as quoted in Moskowitz).
The problem with all this doomsday talk is that the biggest factor in the equation is left out—God. Humans have become so conceited and filled with a false sense of importance that some actually think we not can only predict our planet’s ultimate destruction, but also postpone it if there are still some intelligent scientists (like present ones) who are around when the time comes.
The fallacy of this line of thinking was pointed out almost 2,000 years ago by the inspired apostle Peter. In his second epistle, Peter discussed scoffers who would say: “Where is the promise of His [Jesus’—KB] coming? For since the fathers fell asleep, all things continue as they were from the beginning of creation” (2 Peter 3:4). Notice the uniformitarian assumption of Peter’s scoffers. They assume that all things continue as they are now and will continue that way.
Apply that to Smith’s research. Since the Earth’s orbit is slowing down slightly at the present, he assumes that it will continue to do so for the next 7.6 billion years. But Peter reminds the scoffers that they are willfully forgetting something very important, “that by the word of God the heavens were of old, and the earth standing out of water and in the water, by which the world that then existed perished, being flooded with water” (2 Peter 3:5-6). The key factor in the world’s creation, preservation, and destruction is not ongoing, current natural processes, but the “word of God” that created the world and destroyed life on the Earth in the Flood of Noah. Peter concludes his thoughts by saying: “But the heavens and the earth which now exist are kept in store by the same word, reserved for fire until the day of judgment and perdition of ungodly men” (2 Peter 3:7).
When the Lord enacts His plan to destroy the physical Universe, including our planet Earth, then it will be destroyed, not before (see Butt, 2003). All uniformitarian theories about Earth’s eventual demise are vain mental gymnastics. Instead of looking 7.6 billion years into the future, we all should realize that the destruction of this physical Universe will come as a thief in the night (at any time). “Therefore, since all these things will be dissolved, what manner of persons ought you to be in holy conduct and godliness” (2 Peter 3:11)?
REFERENCES
Butt, Kyle (2003), “What Will Happen When Jesus Comes Again?,” [On-line], URL: http://www.apologeticspress.org/articles/2311.
Moskowitz, Clara (2008), “Earth’s Final Sunset Predicted,” Science.com, [On-line], URL: http://news.yahoo.com/s/space/20080226/sc_space/earthsfinalsunset predicted;_ylt=AtenKy4HBtxHEO3FFWp5w.kiANEA.
Tuesday, March 17, 2009
RAin water Harvesting
The Northeastern hill ranges stretch over six Indian states Assam, Nagaland, Manipur, Mizoram, Tripura and Meghalaya, extending over Bangladesh and northern Myanmar, touching the southern slopes of the Brahmaputra valley and the northern, eastern and southern slopes of the Barak valley. The Meghalaya plateau covers the entire state of Meghalaya and the Karbi hills of Assam. .
The climate and rainfall of the area varies considerably across the region. Encircled by hills and plateaus, rainfall varies even more than temperatures. The average annual rainfall reaches a peak of 13,390 mm in the Cherrapunji-Mawsynram region. But areas that fall in the rainshadow region of the Meghalaya plateau need irrigation. While the northern slopes of the Brahmaputra valley receive an annual average rainfall of 2,500 mm, the area south of the valley and the northern part of Meghalaya receive an annual rainfall of about 2,000 mm.
Distribution of the population in the Northeast is also very uneven. Within the plains there are pockets of very high population density, such as the Manipur plains (400 persons/sq km) and the Nowgong plains (302 persons/sq km). The vast hill tracts, however, have a low population density.
The water resources potential of the region is the largest in the entire country. Given its heavy rainfall, it also has abundant groundwater resources. But only a small part of the region has been studied to estimate the groundwater potential. The maximum scope for development of groundwater exists in Assam, Tripura and Arunachal Pradesh. The available surface water resources have hardly been tapped because of the rugged nature of the terrain. Hence, cultivation in the region is largely rainfed and jhum cultivation (shifting cultivation) has been widely adopted.2
Nonetheless, there are documented instances of some indigenous rainwater harvesting systems used for cultivation, of which some are ingenious. Settled agriculture is practised in the form of irrigated terrace cultivation in parts of Nagaland and a few villages of Meghalaya. Channels are dug to irrigate these fields. The other chief indigenous source of irrigation is the bamboo irrigation system found in parts of Meghalaya, and in some villages in the Mokokchung district of NagalandFriday, January 23, 2009
India debuts 'agricultural Wikipedia'
Content will be continually added and validated through review and analysis by invited agricultural researchers, in a manner similar to that used by Wikipedia and using open source tools, says V. Balaji, head of knowledge management and sharing with the International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), a partner in the project.
The site also houses blogs and forums where anyone can provide and exchange knowledge.
The 85 million-rupee (around US$17 million) project is being implemented over 30 months and is backed by the National Agricultural Innovation Project, a six-year government programme intended to modernise agriculture.
The World Bank and the Indian government have provided the funding for the project and six Indian agricultural and technology institutions are partners in the project, providing information and technological expertise.
India is considered a global leader in promoting innovative ways of using technology for farm and rural outreach, Balaji told SciDev.Net.
In the last five years close to 12,000 information technology-enabled rural information centres — some with Internet access — have been established but there is a lack of accessible agricultural information, he says.
It is hoped that even where farmers have no access to the Internet, the Agropedia information can be used as a basis for radio plays, for example, says Balaji.
Agropedia's lead architect, T. V. Prabhakar of the Indian Institute of Technology in Kanpur, initially envisioned the website as the equivalent of Wikipedia for global agriculture three years ago, but for now it will concentrate on India-specific information.
He says that the initial phase of the project — developing a mechanism to manage the vast repository of knowledge — is nearly completed, and the next step is to develop ways to disseminate the knowledge.
Trials will soon begin in six locations around the country.
Source : http://www.enn.com/top_stories/article/39141
Shree Padre-The Water MAN
Mr. Shree Padre has made impressive strides in farm journalism. He is from Vaninagar, a village in Kerala bordering Karnataka. A farmer by profession, he has been associated with the publications of All India Areca Growers’ Association, Puttur (Karnataka State) since 1987. First with Areca News, a newsletter that became Adike Pathrike in November 1988. He had been the Chief Editor of this unique venture in farm journalism for more than a decade and at present he is its Executive Editor.
Through Adike Pathrike, Mr. Shree Padre has turned the concept of “farmers first” into reality. His efforts through the journal are the fine Indian example of self-help journalism, widely acclaimed for its efficacy the world over, especially in rural communication for development. His talent in photography has helped in providing additional weightage to his write-ups. His style of writing is unique in Kannada journalism.
In recent years, Mr. Shree Padre is working persistently in the field of soil and water conservation in Karnataka and Kerala. He has been conducting awareness programmes on the theme, a unique effort in the region. He has been vigorously collecting and documenting information on rainwater harvesting from world over. Mr. Padre’s series of feature articles on soil and water conservation became an eye-opener for farmers and many experiments based on his articles have been yielding fruitful results in different places. He has written seven books (Six in Kannada and one in English) on rainwater harvesting. Vijaya Karnataka, a Kannada Daily carries his column on water conservation, Hanigoodisona every Wednesday.
To boost his efforts, Mr. Padre has initiated a water forum ‘Jalakoota’ in October 2001. The forum is involved in several activities on soil and water conservation including rainwater harvesting.
Mr. Padre successfully initiated a campaign against the hazardous endosulfan spraying on the cashew plantations in the Kasargod district of Kerala, which had serious repercussions on the health of the villagers.
Email: shreepadre@sancharnet.in
Tel: 91-8251-287234, 91- 04998 - 266148
Address:
Editorial Consultant, Adike Patrike
Post: Vaninagar, Via: Perla - 671 552
Kerala State, INDIA
His blog is: http://jeevajala.blogspot.com
Large differences in lifestyles
The large differences in consumption rates indicate that there are large differences in lifestyle. The consumption rates are lowest for families that live in smaller homes and spend much of their time in the vicinity of the home. They travel less and shorter distances, and in their daily life they make less use of private cars than the others.
Many of the participants of the research project appreciated the comparisons between the various sectors of consumption.Such comparisons made it easier to see in which sectors the consumption rates could be reduced. Others found the results too superficial. Simple comparisons between sectors and with an average consumer were not enough.Participants wished to get more detailed information that could help them to make the right choices.
Some of the participants wanted to know the limit of sustainable consumption, the amount of natural resources that can be safely used by an individual. Based on the presently available information, the researchers cannot give any definite figures. However, it is obvious that less is better. The eco-efficiency discussion has brought forward goals on different levels. In a shorter time perspective, the consumption rates should be reduced down to one fourth of the present level, but a long-term target in the Western countries should be to reduce the consumption of natural resources down to one tenth of the present level.
Many of the participants of the research project appreciated the comparisons between the various sectors of consumption.Such comparisons made it easier to see in which sectors the consumption rates could be reduced. Others found the results too superficial. Simple comparisons between sectors and with an average consumer were not enough.Participants wished to get more detailed information that could help them to make the right choices.
Some of the participants wanted to know the limit of sustainable consumption, the amount of natural resources that can be safely used by an individual. Based on the presently available information, the researchers cannot give any definite figures. However, it is obvious that less is better. The eco-efficiency discussion has brought forward goals on different levels. In a shorter time perspective, the consumption rates should be reduced down to one fourth of the present level, but a long-term target in the Western countries should be to reduce the consumption of natural resources down to one tenth of the present level.
Sunday, January 4, 2009
DYNAMICS OF ERUPTIONS
This section examines the variability of volcanic environments and the physical and chemical controls on eruption dynamics. Environments of volcanism are discussed in terms of plate tectonic theory. Image below is courtesy of Jeffrey Hulen.
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Oceans
Water covers more than 70 per cent of the Earth's surface. Most of this water is contained within four interlinked oceans—the Pacific, which occupies an area larger than all of the world's continents combined, the Atlantic, which is about half the size of the Pacific, the Indian Ocean, and the small, icy Arctic Ocean surrounding the North Pole. The waters around Antarctica are sometimes described as the Southern Ocean, but most geographers regard this region as extensions of the three largest oceans. Despite their vast size, little was known about the oceans until comparatively recently. Before World War I, the ocean floors were believed to be featureless plains. They are now known to have features as irregular as those on land.
Ocean Floor Topography Below sea level, most continents are surrounded by gently sloping continental shelf, which are effectively continuations of the continents. These shelves vary tremendously in width, and may extend as far as 1,500 kilometres (930 miles) out to sea. Many continental shelves are crossed by submarine canyons, some of which are larger than the Grand Canyon. Oceanographers believe these huge depressions were carved out by dense, sediment-loaded water flowing across the seafloor. The continental shelves end at depths of about 130 metres (430 feet). Beyond this point there is a marked change of gradient, where a steep continental slope plunges down to the ocean floor, or abyss. Where the continental slope meets the ocean floor is the continental rise. Sediments wash down from the continental shelf and slope and collect in the rise, which extends up to 1,000 kilometres (620 miles) across the abyss from the continental slope. The abyss proper, which reaches average depths of 4,000 to 6,000 metres (13,000 to 20,000 feet), consists of large abyssal plains broken by low hills. Features of the ocean floor include seamounts, and volcanoes such as the Hawaiian chain, which break the surface as islands. Some extinct, flat-topped volcanoes, such as the Pacific Guyots, are covered by coral deposits, including reefs and atolls.
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| The most prominent features rising from the abyss are mid-oceanic ridge. Formed when magma rises to the surface along separating underwater plate boundaries, these extensive mountain chains are present in all of the oceans. Mid-oceanic ridges cover nearly 23 per cent of the earth's surface, and generally rise about 1,500 metres (5,000 feet) above the ocean floor. Rift valley, bounded by fault zones, may appear along the crests of the ridges where new ocean crust has been formed by the oozing magma. The temperatures of the rocks in this area are higher than normal, demonstrating that the area is volcanically active. Parts of the Mid-Atlantic Ridge, for example, which stretches from the Norwegian Sea to the South Atlantic, emerge as volcanic islands in Iceland and the Azores.
Hot springs were discovered in underwater rift valleys as recently as 1977. Minerals in the hot spring water are deposited around their vents, and build up to form chimneys. Because the water that gushes from these chimneys is dark, they have been named "black smokers". The mineral-rich water around the black smokers, which is often heated to 350C (662F) or more, provides a breeding place for strange bacteria and living creatures, such as blind crabs and tripod fish, formerly unknown to science. Their presence has led to speculation that life may first have evolved on earth in such hostile environments as these. The other main physical features in the oceans are deep trenches, alongside which are chains of volcanoes. Some volcanic chains, such as those in eastern Asia, form islands, while others intrude into adjacent land areas, as in Central and South America. The trenches and ocean ridges are active zones, where the Earth's crust is unstable. They are associated not only with vulcanicity, but also with intense seismic activity. The study of these features helped in the formulation of the theory of plate tectonics, and the recognition that mid-oceanic ridges are plate margins where new crustal rock is being formed as plates move apart, while the trenches mark where plates are being destroyed in subduction zones. The Marianas Trench, on the floor of the North Pacific Ocean, is the deepest known ocean trench, reaching a maximum depth of 11,033 metres (36,198 feet). Plate tectonics explains how the oceans were formed. Around 200 million years ago, all the continents were joined together in one supercontinent called Pangaea. During the last 180 million years, Pangaea has broken up and new oceans have formed through ocean-spreading along rift valleys in the mid-oceanic ridges between the continents. The theory is supported by the fact that none of the basaltic rocks which cover the ocean floor are more than 200 million years old. The oceans, therefore, are young features by comparison with the continents, where rocks have been found that date back around 3.8 billion years. Ocean Water | |
| The oceans contain 97 per cent of the world's water. All of the Earth's natural elements are present in this water, the most common being sodium and chloride, which together form salt. The salinity of ocean water varies between about 3.3 and 3.7 per cent. Areas where the evaporation rate is high and there is little rain generally have a high salinity. Other areas, such as the Baltic Sea, which receive large amounts of fresh water from rivers, are much less saline. Variations in the salinity and temperature of the water in the oceans create density differences in the water, which in turn cause ocean currents. These currents flow through all of the oceans, redistributing the water, transferring heat, and modifying the climate. However, most of the familiar surface currents, such as the warm Gulf Stream which brings mild weather to northwestern Europe, are caused by prevailing winds. The effect of currents on climate were well demonstrated in 1997-1998, when a phenomenon known as El Niño, caused by currents in the Pacific Ocean, caused freak weather conditions in many parts of North and South America, eastern Asia, and Australia. Tides and waves influence the movement of the water in the oceans. Tides are caused by the gravitational pull of the Moon and Sun, which cause the waters in the oceans to rise and fall in a continuous cycle. Winds are normally responsible for the waves. Light winds create calm waters, while choppy waves and rough seas are the result of strong winds. Along the coasts, storm waves bombarding the shore cause erosion, but the most terrifying waves are generated by earthquakes or volcanic eruptions. Called tsunamis, these waves, which are 15 metres (50 feet) or more in height, most frequently occur in the Pacific Ocean. Ocean Life | |
| The oceans are home to an incredible variety of living organisms, ranging from the world's largest animal, the blue whale, to microscopic algae. Around 160,000 ocean species have been named, and scientists believe there may be tens of millions more unclassified. The most important part of the ocean is the euphotic zone, where sunlight can penetrate easily. Beyond this zone, which extends to about 60 metres (200 feet) below the surface, the light becomes too weak to support plant life, and beyond 200 metres (650 feet) it fades away completely. Scientists divide marine life into four main groups: plankton, neuston, nekton, and benthos. Plankton, mostly visible only through a microscope, are found near the surface. They include tiny plants, called phytoplankton, which use sunlight to make their food, and many of which are single-celled, together with microscopic animals collectively known as zooplankton. Crustaceans, which also include many single-celled creatures, make up about 70 per cent of the zooplankton. The copepod, the most common animal in the ocean, is a zooplankton. Much plankton is actually the young of larger ocean species, such as crabs and starfish. Plankton provide the basis of the food chain in the ocean. Neuston are organisms that live at or within 10 to 20 centimetres (4 to 8 inches) of the surface, and include jellyfishes, Portuguese man-of-war, floating snails, and sargassum weed. Nekton, or free-swimming organisms, live mostly near the surface, although some inhabit the dark ocean depths. Among this group are fish, squids, and marine mammals such as whales. Close to the ocean floor dwell the marine organisms collectively known as benthos, among them crabs, lobsters, and starfish, together with fish such as halibut and sole. Other organisms, such as sea grass, become anchored to the ocean floor. Even the deepest ocean trenches, where water pressures are enormous, contain living creatures. Many are scavengers that feed on dead organisms which have drifted down from the top layers. Studying the Ocean | |
| Oceanography began in the second half of the 19th century, and is therefore a relatively young science. One of the most significant early explorations in this field was the round-the-world expedition of a British research ship called Challenger. But while information accumulated about seawater and the myriad life forms it contained, measuring ocean depths was restricted. This was because the only means available before World War I involved lead-weighted ropes or wires, and such a time-consuming, laborious technique was suitable only for shallow coastal waters. From the 1920s, the use of echo-sounders enabled oceanographers to begin the huge task of mapping the ocean floor and, from the 1930s and 1940s, manned descents into the oceans took place in submersibles. Research accelerated after World War II, and the accumulation of information about the ocean floor in the 1950s and 1960s, using increasingly sophisticated techniques, led to the formulation of the theory of plate tectonics. Today the study of "inner space", as the oceans have been called, continues with the aid of research ships, submersibles, satellites, and computers. Overfishing and Pollution | |
| The oceans are an important source of food, minerals, fossil fuels, and energy. Tidal power is already generated, and wave power has potential as an alternative energy supply for the future. However, many formerly rich fishing grounds, such as the Grand Banks off Newfoundland, have been overfished and the cod, for which this fishing ground was once well-known, are now rare. Other misuses of the oceans include oil spills, which are caused by accidents to oil tankers, or the deliberate emptying of oil into the sea when the tankers are cleaned. The dumping of poisonous factory wastes, untreated sewage, or other harmful pollutants, including radioactive wastes, adds to the pollution problem. Two important tropical oceanic environments, where fish and other organisms breed, have been seriously damaged. These are coastal mangrove swamps, which have been polluted and deforested, and coral reefs. A global survey in 1997 suggested that about 95 per cent of coral reefs have been damaged by overfishing, dynamiting, poisoning, pollution, or ships' anchors. The worst damage occurred in the Indo-Pacific region, where there is great demand for reef fish as a delicacy. Global warming could have major effects on the circulation of the oceans and, subsequently, on world climates. For example, computer models suggest that global warming could weaken the Gulf Stream and this would mean much colder winters for northwestern Europe. Global warming could also melt ice locked in the global ice packs and release it into the oceans, where it would cause sea levels to rise and low-lying islands, such as the Maldives, to be submerged within a century. The conservation of the oceans and their valuable resources is a matter for urgent coordinated international action. | |
Plate Tectonics
| According to the theory of plate tectonics, the earth’s crust is broken up into at least a dozen rigid plates that move independently of one another. These slabs rest upon a layer of heated, pliable rock called the asthenosphere, which flows slowly like hot tar. Geologists have not yet determined exactly how these two layers interact, but a popular theory is that the movement of the thick, molten material in the asthenosphere forces the upper plates to shift, sink, or rise. The basic concept behind plate tectonics is simply that heat rises. Hot air rises above cool air, and warm water currents flow above cold water. The same is true of the heated rock below the earth’s surface. The asthenosphere’s molten material, or magma, pushes upwards, while cooler, hardened matter sinks deeper into the mantle. | 
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| Sinking rock eventually reaches the extremely hot temperatures of the lower asthenosphere, heats up, and begins to rise again. This continual, roughly circular motion is called convection. At diverging plate boundaries and at hot spots in the otherwise solid lithosphere, molten material wells up to the surface, forming a new crust. Continental Drift | |
| The theory of plate tectonics was not widely accepted until the 1960s and 1970s. Before that time, most scientists believed the earth’s continents and oceans to be stationary. At the beginning of the 20th century, German meteorologist Alfred Wegener suggested that all continents had been part of one huge supercontinent, Pangaea. According to Wegener, about 200 million years ago Pangaea broke into separate plates that slowly drifted away from each other, leading to today’s continental arrangement. One of Wegener’s most convincing pieces of evidence was the almost perfect fit between the eastern coast of South America and the western coast of Africa. To support his theory, he pointed out that rock formations on opposite sides of the Atlantic—in Brazil and West Africa—match in age, type, and structure. Also, the formations often contain fossils of the same terrestrial creatures, indicating that South America and Africa must have previously been connected. In subsequent years, scientific discoveries steadily began to support the fundamental aspects of Wegener’s theory. Geologists demonstrated the existence of the slowly moving asthenosphere, underlying the crust at depths of 50 to 150 kilometres (30 to 80 miles). In addition, scientists in the 1920s used sonar, an echo-sounding device, to determine ocean depths and map the seafloor. They concluded that the Mid-Atlantic Ridge, detected in the 19th century, was part of a worldwide ocean ridge system. | |
| Seafloor Spreading | |
| Additional evidence for plate tectonics came in the 1950s and 1960s. During this period, scientists discovered that all rock fragments maintain a set magnetic pattern based on when the rocks formed. Geophysicists also learned that the earth’s magnetic field had reversed between north and south dozens of times over millions of years. With this knowledge, they examined both sides of ocean ridges and found that the rocks on one side of the ridge produced a mirror-image geomagnetic pattern of the rocks on the other side. | |
| The rocks nearest the ridge were relatively young, but the rocks aged as the distance from the ridge increased. In addition, marine sediment was thicker and older further from the ridge, whereas the ridge itself had virtually no deposits of sediment. These observations, added to those of the heat flow at the ridge, confirmed the creation of new crust at mid-ocean ridges and the mechanism of seafloor spreading. |  |
| After molten rock reaches the seafloor as lava, deep ocean water quickly cools and consolidates the material. To make room for this continual addition of new crust, the plates on either side of the ridge must constantly move apart. In the North Atlantic, the rate of movement of each plate is only about 1 to 2 centimetres (0.4 to 0.8 of an inch) per year. In the Pacific, the rate can be more than 10 centimetres (about 4 inches) annually. | |
| Subduction | |
| The Marianas Trench, just east of the Mariana Islands in the western Pacific, is the deepest seafloor depression in the world at 11,033 metres (36,198 feet). The Marianas Trench is one of many deepwater trenches formed by the geologic process of subduction. During subduction, the edges of plates are subducted, or forced under, other plates. Ocean crust is drawn down into the mantle and partially melted. |  |
| An important effect of the melting of subducted ocean crust is the production of new magma. When subducted ocean crust melts, the magma that forms may rise from the plane of subduction deep within the mantle, erupting on the earth’s surface. Eruption of magma melted by subduction has created long, arc-shaped chains of volcanic islands, such as Japan, the Philippines, and the Aleutians. Where an oceanic plate is subducted beneath continental crust, the magma produced by subductive melting erupts from volcanoes situated among long, linear mountain chains, such as the Andes in South America. Plate Boundaries | |
| Plate boundaries do not necessarily match the coastlines of continents. A plate can consist of continental crust, oceanic crust, or both. In most cases, continents are part of larger plates that extend for hundreds of miles offshore. Many plate boundaries are far out in the middle of the ocean. There are three types of plate boundaries: divergent, convergent, and transform. Divergent boundaries exist where plates move away from each other, pushed apart by heated, material moving upwards from the asthenosphere. An additional force involved in divergence may be the subduction of the heavier, older, and thicker crust at the opposite ends of each diverging plate. As the heavy edge sinks, it pulls the rest of the plate with it, away from the divergent boundary. Magma at the divergent boundary hardens, adding new crust to the edges of the separating plates. Scientists often refer to these as constructive boundaries, due to the construction of new material. Mid-ocean ridges are examples of this type of boundary. These ridges frequently resemble submarine mountain ranges, portions of which are high enough to break the ocean’s surface, in places such as Iceland in the North Atlantic. Divergent boundaries also exist within continents. The Great Rift Valley, which extends for more than 4,830 kilometres (3,000 miles) from Syria to Mozambique, is a well-known example. Divergence has caused the earth’s crust to thin and drop along this plate boundary. A boundary where two plates collide is a convergent boundary. When an oceanic plate, such as the Nazca Plate which moves eastwards under the southeastern Pacific Ocean, meets a continental edge such as South America, the denser and heavier oceanic crust is normally subducted and partially melted beneath the continental plate. Ocean trenches at the boundary of the plate and mountain chains on the continental plate often result. | |
| Earthquakes can occur at these plate margins, shifting plates by up to 5 metres (about 15 feet) at once. Such faults exist in Chile, Japan, Taiwan, the Philippines, New Zealand, and Sumatra. When two continental plates collide, the crust from both plates thrusts upwards, creating mountain chains. The collision of India with the Asian continent formed the Himalayas. In fact, the mountain range is still growing in height today because India and Asia are still converging. |  |
| At a transform boundary, plates move past each other in opposite directions. Little volcanic activity accompanies transform boundaries, but large, shallow earthquakes can occur. The San Andreas Fault in California (USA), is the most famous example of this type of boundary. Mid-ocean ridges are offset by hundreds of small transforms. | |
| The revolutionary theory of plate tectonics forms the basis of modern geologic thought and explains many of today’s landforms and the movement of continents. This theory also provides an explanation for many of the world’s earthquakes and volcanoes. Most earthquakes and volcanic eruptions take place near plate margins. |  |
| Unfortunately, many large cities exist along plate margins, such as along the Ring of Fire, a zone of intense volcanic and seismic activity surrounding the Pacific Ocean. Humans repeatedly suffer the effects of these often catastrophic manifestations of tectonic activity. | |
Earthquakes
Earthquakes occur when the Earth’s crust moves suddenly along a fault. Rock under great strain ruptures and releases energy in the form of seismic waves. However, most earthquakes are so slight that they are not felt by humans. Some quakes create vibrations resembling those caused by the passing of a heavy truck. The vibrations of major earthquakes can be catastrophically destructive, having the ability to level entire cities in seconds.
History of Earthquake Study
Since ancient times, people living in earthquake-prone areas have been preoccupied with earthquakes. Some of the ancient Greek philosophers attributed them to subterranean winds; others blamed them on fires deep in the Earth. Around AD 130, the Chinese scholar Zhang Heng reasoned that waves must ripple through the Earth from the source of an earthquake. He constructed an elaborate bronze vessel to record the passage of such waves and delicately balanced eight balls in the mouths of eight dragons placed around the circumference of the vessel. A passing seismic wave would cause one or more of the balls to drop.
In the early 20th century, the Russian seismologist Prince Boris Golitzyn invented the modern seismograph. His device, using a magnetic pendulum suspended between the poles of an electromagnet, ushered in the modern era of earthquake research.
Kinds and Locations of Earthquakes
Scientists recognize three general classes of earthquakes: tectonic, volcanic, and artificially produced. The tectonic variety is by far the most devastating, and such quakes pose particular difficulties for scientists trying to develop ways to predict them.
According to the theory of plate tectonics, the ultimate cause of tectonic earthquakes is stresses set up by movements of the dozen or so major and minor plates that make up the Earth’s crust. Most tectonic quakes occur at the boundaries of these plates, in zones where one plate slides past or beneath another.
Earthquakes resulting from subduction account for nearly half of the world's destructive seismic events and three-quarters of the Earth's seismic energy. These are concentrated along the Ring of Fire, a narrow band about 38,600 kilometres (24,000 miles) long, which coincides with the margins of the Pacific Ocean. Crustal rupture in such earthquakes tends to occur far below the Earth's surface, at depths of up to 645 kilometres (400 miles).
Tectonic earthquakes beyond the Ring of Fire occur in a variety of geological settings. Mid-ocean ridges are the sites of numerous such events of moderate intensity that take place at relatively shallow depths. Humans rarely feel these quakes. Such earthquakes account for only about 5 per cent of the Earth's seismic energy, but the instruments of the worldwide network of seismological stations record them daily.
Tectonic earthquakes also occur in a zone stretching from the Mediterranean and Caspian seas to the Himalayas, and ending in the Bay of Bengal. Within this zone, which releases about 15 per cent of the Earth's seismic energy, continental land masses riding on the Eurasian, African, and Indo-Australian plates are forced together to produce high, young mountain chains. The resulting earthquakes, which occur at shallow to intermediate depths, have devastated areas of Portugal, Algeria, Morocco, Italy, Greece, Iran, India, FYRO Macedonia, Turkey, and other countries partly or entirely on the Balkan Peninsula.
One other category of tectonic earthquakes includes the infrequent but large and destructive ones that occur in areas far removed from other forms of tectonic activity. Prime examples of these so-called mid-plate earthquakes are three massive tremors that shook the central United States region around New Madrid, Missouri, in 1811 and 1812. Powerful enough to be felt 1,600 kilometres (1,000 miles) away, these shocks produced movements that rerouted the course of the Mississippi River. Geologists believe that the New Madrid earthquakes are symptomatic of forces tearing apart the Earth’s crust—forces such as those that created Africa’s Great Rift Valley.
Of the two classes of non-tectonic earthquakes, those of volcanic origin are seldom large or destructive. They are of interest chiefly because they herald impending volcanic eruptions, as they did in the weeks preceding the eruption in 1980 of Mount St Helens in the northwest United States. Such earthquakes originate as magma works its way upwards, filling the chambers beneath a volcano. As the flanks and summit of the volcano swell, swarms of small earthquakes signal the rupture of stressed rocks. On the island of Hawaii, seismographs register as many as 1,000 small quakes a day before an eruption occurs.
Humans may contribute to the cause of earthquakes through a variety of activities such as filling new reservoirs, detonating underground atomic explosives, or pumping fluids deep into the ground through wells. For example, in 1962 Denver, Colorado, in the United States began to experience earthquakes for the first time in its history. The tremors coincided with the pumping of waste fluids into deep wells at an arsenal east of the city. After officials discontinued the pumping, the earthquakes persisted for a while and then ceased.
Earthquake Effects
Earthquakes produce various adverse effects to the inhabitants of seismically active regions. They can cause great loss of life by destroying structures such as buildings, bridges, and dams. Earthquakes can also trigger devastating landslides. Massive fires caused by the rupture of gas and electrical lines have damaged or destroyed many cities.
Another destructive effect of an earthquake is the generation of a so-called tidal wave. This type of wave is caused by sub-sea tremors, not tides, so it is more properly called a seismic sea wave or (its Japanese name) tsunami. These towering walls of water have struck populated coastlines, destroying entire towns. Sanriku, Japan, a town with a population of 20,000, suffered such a devastating fate in 1896.
Liquefaction of soils is another seismic hazard. When subjected to the shock waves of an earthquake, soil used in landfill may lose virtually all its bearing strength and become similar to quicksand. Buildings have literally been swallowed up by these materials.
After a major earthquake, there may be a series of further tremors, some of them severe enough to cause additional damage. These tremors are called aftershocks.
Richter Scale
Seismologists have devised several scales of measurement to describe earthquakes quantitatively. One is the Richter scale—named after the US seismologist Charles Francis Richter (1900–1985)—which measures the energy released at the focus of a quake. It is a logarithmic scale that runs from 1 to 9: a magnitude 7 earthquake is 10 times more powerful than a magnitude 6 earthquake, 100 times more powerful than one of magnitude 5, 1,000 times more powerful than one of magnitude 4, and so on. About 800 earthquakes of magnitudes 5 to 6 occur annually worldwide, in comparison with about 50,000 earthquakes of magnitudes 3 to 4, and only about one earthquake of magnitudes 8 to 9.
Theoretically, the Richter scale is an open-ended one, but until 1979 an earthquake of magnitude 8.5 was thought to be the most powerful possible. Since then, however, improvements in seismic measuring techniques have enabled seismologists to refine the scale, and they now consider 9.5 to be the practical limit.
Devastating Earthquakes
Historical records of earthquakes before the mid-18th century are generally lacking or unreliable. However, reasonably trustworthy records do exist for the following ancient earthquakes: one off the coast of Greece in 425 BC that created the island of Évvoia, one that destroyed the city of Ephesus in Asia Minor in AD 17, one that levelled much of Pompeii in 63, and those that partially destroyed Rome in 476 and Constantinople (now Istanbul) in 557 and again in 936. Severe earthquakes struck England in 1318, Naples in 1456, and Lisbon in 1531.
The 1556 earthquake in Shaanxi Province of China, which killed about 800,000 people, was one of the greatest natural disasters in history. In 1693, an earthquake in Sicily resulted in a loss of approximately 60,000 lives. In the early 18th century the Japanese city of Edo (the site of modern Tokyo) was destroyed, with the loss of some 200,000 lives. In 1755 the city of Lisbon was devastated by an earthquake and about 60,000 people died, a disaster which the French writer Voltaire wrote about in his novel Candide. An earthquake shook Quito, now the capital of Ecuador, in 1797, and more than 40,000 people died.
In North America, the series of earthquakes that struck southeastern Missouri in 1811 and 1812 was probably the most powerful experienced in the United States in modern history. The most famous US earthquake is the one that shook the area of San Francisco in 1906, causing extensive damage and resulting in the loss of 700 lives.
Among the most recent earthquakes was the one on 17 January 1995 that severely damaged Kobe, Japan, killing more than 4,000 people and leaving over 275,000 people homeless. The earthquake measured 7.2 on the Richter scale and lasted 20 seconds. On 28 May 1995 an earthquake measuring 7.5 on the Richter scale struck Neftegorsk, Russia, an oil-producing town on Sakhalin Island in the far eastern part of the country. The earthquake caused great destruction, killing more than 2,000 people and demolishing blocks of flats. In China’s Yunnan Province, near Lijiang, a tremor of magnitude 7.0 struck on 3 February 1996, killing more than 300 people, seriously injuring another 3,800, and damaging or destroying an estimated 830,000 homes.
Preparing for Earthquakes
Countries in earthquake-prone areas, such as Japan, have placed great emphasis on researching and implementing state-of-the-art building construction that will be able to withstand earthquakes. Communities have established and rehearsed detailed emergency procedures. Yet even Tokyo, despite being among the best-prepared nations to deal with earthquakes in the world, is vulnerable to serious damage and heavy loss of life. Tokyo’s problems include: soft soil in some locales that may easily liquefy; a large number of old, buildings of weak construction; narrow streets that would be rendered impassable after earthquake damage; and highly flammable refineries in the industrial areas.
Earthquake Prediction
Attempts to predict when and where earthquakes will occur have met with some success in recent years. China, Japan, Russia, and the United States are the countries most actively supporting such research. In 1975 the Chinese predicted an earthquake of magnitude 7.3 at Haicheng, evacuating 90,000 residents only two days before it destroyed or damaged 90 per cent of the city’s buildings. One of the clues that led to this prediction was a chain of low-magnitude tremors, called foreshocks, that had begun about five years earlier in the area.
Other potential clues being studied are the tilting or bulging of the land surface and changes in the Earth’s magnetic field, in the water-levels of wells, and even in the behaviour of animals. A new method currently being studied involves measuring the buildup of stress in the Earth’s crust. Most predictions are only rough estimates, but as advancements are made in seismology and plate tectonics, the accuracy of predictions will improve, leading to earlier warnings and fewer deaths.
History of Earthquake Study
Since ancient times, people living in earthquake-prone areas have been preoccupied with earthquakes. Some of the ancient Greek philosophers attributed them to subterranean winds; others blamed them on fires deep in the Earth. Around AD 130, the Chinese scholar Zhang Heng reasoned that waves must ripple through the Earth from the source of an earthquake. He constructed an elaborate bronze vessel to record the passage of such waves and delicately balanced eight balls in the mouths of eight dragons placed around the circumference of the vessel. A passing seismic wave would cause one or more of the balls to drop.
In the early 20th century, the Russian seismologist Prince Boris Golitzyn invented the modern seismograph. His device, using a magnetic pendulum suspended between the poles of an electromagnet, ushered in the modern era of earthquake research.
Kinds and Locations of Earthquakes
Scientists recognize three general classes of earthquakes: tectonic, volcanic, and artificially produced. The tectonic variety is by far the most devastating, and such quakes pose particular difficulties for scientists trying to develop ways to predict them.
According to the theory of plate tectonics, the ultimate cause of tectonic earthquakes is stresses set up by movements of the dozen or so major and minor plates that make up the Earth’s crust. Most tectonic quakes occur at the boundaries of these plates, in zones where one plate slides past or beneath another.
Earthquakes resulting from subduction account for nearly half of the world's destructive seismic events and three-quarters of the Earth's seismic energy. These are concentrated along the Ring of Fire, a narrow band about 38,600 kilometres (24,000 miles) long, which coincides with the margins of the Pacific Ocean. Crustal rupture in such earthquakes tends to occur far below the Earth's surface, at depths of up to 645 kilometres (400 miles).
Tectonic earthquakes beyond the Ring of Fire occur in a variety of geological settings. Mid-ocean ridges are the sites of numerous such events of moderate intensity that take place at relatively shallow depths. Humans rarely feel these quakes. Such earthquakes account for only about 5 per cent of the Earth's seismic energy, but the instruments of the worldwide network of seismological stations record them daily.
Tectonic earthquakes also occur in a zone stretching from the Mediterranean and Caspian seas to the Himalayas, and ending in the Bay of Bengal. Within this zone, which releases about 15 per cent of the Earth's seismic energy, continental land masses riding on the Eurasian, African, and Indo-Australian plates are forced together to produce high, young mountain chains. The resulting earthquakes, which occur at shallow to intermediate depths, have devastated areas of Portugal, Algeria, Morocco, Italy, Greece, Iran, India, FYRO Macedonia, Turkey, and other countries partly or entirely on the Balkan Peninsula.
One other category of tectonic earthquakes includes the infrequent but large and destructive ones that occur in areas far removed from other forms of tectonic activity. Prime examples of these so-called mid-plate earthquakes are three massive tremors that shook the central United States region around New Madrid, Missouri, in 1811 and 1812. Powerful enough to be felt 1,600 kilometres (1,000 miles) away, these shocks produced movements that rerouted the course of the Mississippi River. Geologists believe that the New Madrid earthquakes are symptomatic of forces tearing apart the Earth’s crust—forces such as those that created Africa’s Great Rift Valley.
Of the two classes of non-tectonic earthquakes, those of volcanic origin are seldom large or destructive. They are of interest chiefly because they herald impending volcanic eruptions, as they did in the weeks preceding the eruption in 1980 of Mount St Helens in the northwest United States. Such earthquakes originate as magma works its way upwards, filling the chambers beneath a volcano. As the flanks and summit of the volcano swell, swarms of small earthquakes signal the rupture of stressed rocks. On the island of Hawaii, seismographs register as many as 1,000 small quakes a day before an eruption occurs.
Humans may contribute to the cause of earthquakes through a variety of activities such as filling new reservoirs, detonating underground atomic explosives, or pumping fluids deep into the ground through wells. For example, in 1962 Denver, Colorado, in the United States began to experience earthquakes for the first time in its history. The tremors coincided with the pumping of waste fluids into deep wells at an arsenal east of the city. After officials discontinued the pumping, the earthquakes persisted for a while and then ceased.
Earthquake Effects
Earthquakes produce various adverse effects to the inhabitants of seismically active regions. They can cause great loss of life by destroying structures such as buildings, bridges, and dams. Earthquakes can also trigger devastating landslides. Massive fires caused by the rupture of gas and electrical lines have damaged or destroyed many cities.
Another destructive effect of an earthquake is the generation of a so-called tidal wave. This type of wave is caused by sub-sea tremors, not tides, so it is more properly called a seismic sea wave or (its Japanese name) tsunami. These towering walls of water have struck populated coastlines, destroying entire towns. Sanriku, Japan, a town with a population of 20,000, suffered such a devastating fate in 1896.
Liquefaction of soils is another seismic hazard. When subjected to the shock waves of an earthquake, soil used in landfill may lose virtually all its bearing strength and become similar to quicksand. Buildings have literally been swallowed up by these materials.
After a major earthquake, there may be a series of further tremors, some of them severe enough to cause additional damage. These tremors are called aftershocks.
Richter Scale
Seismologists have devised several scales of measurement to describe earthquakes quantitatively. One is the Richter scale—named after the US seismologist Charles Francis Richter (1900–1985)—which measures the energy released at the focus of a quake. It is a logarithmic scale that runs from 1 to 9: a magnitude 7 earthquake is 10 times more powerful than a magnitude 6 earthquake, 100 times more powerful than one of magnitude 5, 1,000 times more powerful than one of magnitude 4, and so on. About 800 earthquakes of magnitudes 5 to 6 occur annually worldwide, in comparison with about 50,000 earthquakes of magnitudes 3 to 4, and only about one earthquake of magnitudes 8 to 9.
Theoretically, the Richter scale is an open-ended one, but until 1979 an earthquake of magnitude 8.5 was thought to be the most powerful possible. Since then, however, improvements in seismic measuring techniques have enabled seismologists to refine the scale, and they now consider 9.5 to be the practical limit.
Devastating Earthquakes
Historical records of earthquakes before the mid-18th century are generally lacking or unreliable. However, reasonably trustworthy records do exist for the following ancient earthquakes: one off the coast of Greece in 425 BC that created the island of Évvoia, one that destroyed the city of Ephesus in Asia Minor in AD 17, one that levelled much of Pompeii in 63, and those that partially destroyed Rome in 476 and Constantinople (now Istanbul) in 557 and again in 936. Severe earthquakes struck England in 1318, Naples in 1456, and Lisbon in 1531.
The 1556 earthquake in Shaanxi Province of China, which killed about 800,000 people, was one of the greatest natural disasters in history. In 1693, an earthquake in Sicily resulted in a loss of approximately 60,000 lives. In the early 18th century the Japanese city of Edo (the site of modern Tokyo) was destroyed, with the loss of some 200,000 lives. In 1755 the city of Lisbon was devastated by an earthquake and about 60,000 people died, a disaster which the French writer Voltaire wrote about in his novel Candide. An earthquake shook Quito, now the capital of Ecuador, in 1797, and more than 40,000 people died.
In North America, the series of earthquakes that struck southeastern Missouri in 1811 and 1812 was probably the most powerful experienced in the United States in modern history. The most famous US earthquake is the one that shook the area of San Francisco in 1906, causing extensive damage and resulting in the loss of 700 lives.
Among the most recent earthquakes was the one on 17 January 1995 that severely damaged Kobe, Japan, killing more than 4,000 people and leaving over 275,000 people homeless. The earthquake measured 7.2 on the Richter scale and lasted 20 seconds. On 28 May 1995 an earthquake measuring 7.5 on the Richter scale struck Neftegorsk, Russia, an oil-producing town on Sakhalin Island in the far eastern part of the country. The earthquake caused great destruction, killing more than 2,000 people and demolishing blocks of flats. In China’s Yunnan Province, near Lijiang, a tremor of magnitude 7.0 struck on 3 February 1996, killing more than 300 people, seriously injuring another 3,800, and damaging or destroying an estimated 830,000 homes.
Preparing for Earthquakes
Countries in earthquake-prone areas, such as Japan, have placed great emphasis on researching and implementing state-of-the-art building construction that will be able to withstand earthquakes. Communities have established and rehearsed detailed emergency procedures. Yet even Tokyo, despite being among the best-prepared nations to deal with earthquakes in the world, is vulnerable to serious damage and heavy loss of life. Tokyo’s problems include: soft soil in some locales that may easily liquefy; a large number of old, buildings of weak construction; narrow streets that would be rendered impassable after earthquake damage; and highly flammable refineries in the industrial areas.
Earthquake Prediction
Attempts to predict when and where earthquakes will occur have met with some success in recent years. China, Japan, Russia, and the United States are the countries most actively supporting such research. In 1975 the Chinese predicted an earthquake of magnitude 7.3 at Haicheng, evacuating 90,000 residents only two days before it destroyed or damaged 90 per cent of the city’s buildings. One of the clues that led to this prediction was a chain of low-magnitude tremors, called foreshocks, that had begun about five years earlier in the area.
Other potential clues being studied are the tilting or bulging of the land surface and changes in the Earth’s magnetic field, in the water-levels of wells, and even in the behaviour of animals. A new method currently being studied involves measuring the buildup of stress in the Earth’s crust. Most predictions are only rough estimates, but as advancements are made in seismology and plate tectonics, the accuracy of predictions will improve, leading to earlier warnings and fewer deaths.
Volcanoes
The build-up of molten rock in a volcano before it erupts is like the gases in a shaken bottle of champagne. If the amount of gas in a volcano’s magma is high, the inevitable release leads to massive explosions. |  |
| The amount of gas inside magma—molten rock—is one of the most important indicators determining how violent an eruption will be. The viscosity, or thickness, of magma is another important factor. Under ground, gases remain suspended under pressure in the magma, but when magma rises to the lower pressures of the surface, the gases expand. Volcanoes with less gaseous and more fluid magma usually have less violent eruptions because the small amount of gas easily escapes from the lava into the air. Thick, sticky magma, on the other hand, slows down the escape of gases and may also block a volcano’s main vent. When the gases are finally released, they burst out of the lava in furious and turbulent blasts. These explosive eruptions are characterized by large clouds of flying rock particles, rather than lava flows. Volcanic Products | |
| Volcanoes emit a variety of substances, with varying degrees of force. These substances are lava, pyroclastic material, ash, and gases. Lava is magma that reaches the surface. This liquefied rock is many times hotter than boiling water and glows bright yellow, orange, and red. Lava may erupt in explosive bursts, like giant fountains, or flow gently down the slopes of a mountain. Lava can leave a volcano from the top vent or emerge from vents along the sides. Except for the molten rock that lands back inside the main crater to continue bubbling, all lava eventually cools and solidifies. Some lava cools quickly, on or near the volcano, but more fluid lava may travel for miles before slowly congealing into rock. Over time, solidified lava from different eruptions steadily increases the size and height of the volcano. |  |
| All fragments thrown into the air by a volcanic eruption are called pyroclastics. During a more violent eruption, the force of the blast sends superhot gas and millions of pieces of lava into the air. These particles are classified as bombs, cinders, or ash, depending on their size and shape. Small pieces of lava, which solidify almost immediately, form slivers of volcanic glass. Together with rocks blown from the sides of a volcano, the entire collection of ejected material becomes a hot, fast-moving cloud of rock and ash. These flows can travel at great speed down the flanks of a volcano and into surrounding areas, causing extensive destruction. In 1902 the eruption of Mount Pelée, on the island of Martinique, created this type of pyroclastic blast and destroyed the town of Saint-Pierre, killing about 30,000 people. Like lava, pyroclastic material raining down on a volcano eventually compacts into solid layers that build up the volcano’s bulk. Some eruptions actually reduce the height of a volcano, because they are so powerful that they literally blow the top of the volcano off. In 1883 the cataclysmic explosion of Krakatau in Indonesia destroyed most of the island, which had been formed by the volcano. Volcanoes often spew great quantities of ash many kilometres into the air. This fine ash can drift for thousands of kilometres, falling on distant lands, yet the smallest particles of dust may remain suspended in the atmosphere for months. The uprush of gas and vapours from the Krakatau eruption reportedly carried fine ash to a height of 27 kilometres (17 miles). In addition to creating colourful sunsets for many months afterwards, the vapour and ash clouds can have long-lasting effects on the atmosphere and climate. Steam and other gases such as carbon dioxide, hydrogen, carbon monoxide, and sulphur dioxide continuously escape from the surface of lava. Volcanic areas can emit harmful gases in immense quantities. In 1986 a volcanic lake in northern Cameroon released toxic gases that killed more than 1,700 people. The danger to life posed by active volcanoes is not limited to the eruption of molten rock or showers of ash and cinders. Disastrous mudflows are an equally serious hazard. One triggered by a small eruption that melted ice and snow on Ruiz Peak volcano in Colombia claimed more than 25,000 lives in 1985, one of the worst volcanic disasters in the 20th century. Some mudflows may occur long after an eruption is over, when heavy rains saturate loose volcanic debris. In addition, eruptions near glaciers can melt vast quantities of ice, resulting in damaging floods. Iceland occasionally suffers these massive floods, known there as Jökulhlaup. | |
| Volcanic Landforms | |
| The shapes of volcanoes vary according to the types of particles thrown from the volcano during eruptions. The beautifully symmetrical cones of Mount Fuji in Japan and Mayon in the Philippines are examples of strato-volcanoes, or composite volcanoes. This type of volcano emits a combination of lava and pyroclastic material. The mixture allows the successive layers to solidify and support additional mass. Strato-volcanoes are the highest and steepest volcanoes in the world. |  |
| Volcanoes that consist predominantly of pyroclastic materials are called cinder cones. These mountains, such as Capulin Mountain in New Mexico (USA), are easily eroded and usually do not reach great heights. Shield volcanoes, on the other hand, are predominantly lava-based landforms that have gradual slopes and wide bases, because they release fluid lava slowly. These volcanoes can create huge landforms. Mauna Loa and Mauna Kea on the island of Hawaii (The Big Island) are classic examples: Mauna Kea has a base on the ocean floor more than 200 kilometres (120 miles) wide. Under certain circumstances, instead of issuing from a central vent, lava pours out along cracks, or fissures, that may extend for several kilometres across the land surface. Flows of this sort have created thick sheets of basalt covering thousands of square kilometres. The Deccan Plateau in India, which covers more than 500,000 square kilometres (200,000 square miles), was formed in this way. The Columbia Plateau in the northwest United States is another example. In modern times, fissure eruptions on a smaller scale have been observed in Iceland and Hawaii. Some enormous, craterous basins called calderas, at the top of long-dormant or extinct volcanoes, form when a massive explosion forces the upper part of a volcano to collapse. Some of these calderas eventually fill with water, forming deep lakes, such as the picturesque Crater Lake in the northwest US. | |
| States of Volcanic Activity | |
| Volcanoes can be active, dormant, or extinct. Active volcanoes have erupted in a relatively recent period. There are more than 500 active volcanoes on continents or islands; thousands more exist under the oceans. Many active volcanoes are in the Ring of Fire, a zone of seismic and volcanic activity that encircles the Pacific Ocean. Izalco Volcano, in El Salvador, has been erupting since 1770. Other active volcanoes include Stromboli in the Aeolian Islands near Sicily, and Cotopaxi in the Andes of Ecuador. |  |
| Dormant volcanoes are those that have not erupted for many years, but have the potential to erupt again. The eruption that follows prolonged dormancy is usually violent, as was the explosion in 1980 of Mount Saint Helens in the northwest US, after 123 years of inactivity. The massive eruption in 1991 of Mount Pinatubo, in the Philippines, came after six centuries of dormancy. Extinct volcanoes have not erupted in thousands of years and show no signs of doing so in the future. Mount Kenya, the second highest mountain in Africa, is an extinct volcano. Edinburgh Castle, in Scotland, sits on top of an extinct volcano. | |
| Creation of Volcanoes Most active volcanoes ultimately derive their energy from processes associated with the theory of plate tectonics. Volcanoes tend to coincide with major plate boundaries, though some, like the Hawaiian Islands, formed over hot spots in the earth's surface far from plate boundaries. |  |
| At subduction zones, where one plate moves beneath the other, the subducted plate is dragged downwards into the earth's mantle until it reaches a depth where high temperatures partially melt the rock. The resulting magma then rises along vertical fissures and reaches the surface through a volcanic vent. Volcanoes along the Andes in South America and the Cascade Range in North America are examples of volcanoes that formed on continental crust overlying subduction zones. When fissures open up on the seafloor, volcanic islands form as a result, such as Japan and the Philippines. At divergent plate boundaries, where two plates move away from each other, magma wells up along the linear boundary. Iceland is a volcanic land mass on top the Mid-Atlantic Ridge, a divergent plate boundary. New additions along this ridge, such as the island of Surtsey, still continue to be created. A third type, known as transform boundaries, exists when two plates slide alongside each other. The interaction of plates at a transform boundary, such as the San Andreas Fault in the western United States, does not normally lead to volcanic activity. | |
| Hot Spots Hundreds of hot spots exist around the world. These are areas in the lithosphere that are underlain by unusually hot magma. This heat causes partial melting of the lithosphere, eventually leading to volcanic activity. The Hawaiian Islands are a classic example of a volcanic grouping formed over one hot spot. |  |
| Over thousands of years, as the Pacific Plate inched its way in a northwest direction, the stationary hot spot underneath the plate successively created volcanoes above it. Several of these volcanoes reached the ocean’s surface, forming the Hawaiian Islands. As the plate continued to move, volcanoes, embedded in the plate, travelled away from the source of magma and eventually became extinct. This hot spot still continues to create new volcanoes. Thus, the islands are progressively younger from the northwest to the southeast. Several volcanoes in the chain are still quite active, and new underwater volcanoes are forming to the southeast of Hawaii as the Pacific Plate continues to move over the hot spot. Humans and Volcanoes | |
| Volcanoes are an important aspect of many cultures. One of the most famous and beautiful volcanoes in the world is Mount Fuji in Japan, which last erupted in 1708. According to legend, Mount Fuji arose from the plain during a single night in 286 BC. Geologically, the mountain is much older than the legend asserts. Certain religious sects regard the mountain as a sacred place. Thousands of pilgrims from all parts of the country visit Mount Fuji annually, and numerous shrines and temples are on its slopes. Mount Fuji is also revered in Japanese literature and art. Volcanoes, when not causing mass destruction, can actually benefit humans. For example, they may provide extremely fertile land for crops and forests. Vineyards and orchards now cover the lower slopes of Mount Vesuvius, which destroyed the town of Pompeii in AD 79 in a pyroclastic explosion. Higher up, oaks and chestnut trees grow. Volcanoes, when inactive, can also provide areas for sightseeing, hiking, and camping, and many have become parks. Tourism often results from continuous or recent volcanic eruptions. Many people visit Hawaii Volcanoes National Park to view the spectacular lava flows from a safe distance. Scientific Inquiry | |
| Geologists and volcanologists, who specifically study volcanoes, attempt to increase our knowledge of volcanoes and try to predict when eruptions will occur. Volcanic earthquakes and changes in the shape of volcanoes are two signals of impending eruptions. Like earthquakes, however, volcanoes can be unpredictable, and those who live in their vicinity are constantly at risk. | |
Nutrients in water benefits agriculture
Agriculture producers may find they don't have to bottle their water from the Seymour Aquifer in the Rolling Plains to make it more valuable, according to Texas AgriLife Research scientists.
Drs. John Sij, Cristine Morgan and Paul DeLaune have studied nitrate levels in irrigation water from the Seymour Aquifer for the past three years, and have found nitrates can be as high as 40 parts per million. Though unacceptable for drinking, the water would benefit agricultural producers who use it for irrigation.
This high concentration of nitrates is a concern because it exceeds the federal safe drinking water standards as the aquifer is used as a municipal water source for the communities of Vernon, Burkburnett and Electra, as well as some rural families, Sij said.
"When you get more than 10 parts per million, it exceeds the federal limit," he said. "Our water at Chillicothe is around 20 parts per million, so we don't give it to the babies, but adults can drink it."
Nitrate levels range from 3 parts per million to 40 parts per million in the aquifer, so the situation is being addressed by the Texas State Soil and Water Conservation Board, with grant funding from the Environmental Protection Agency.
Also working on the project are the Haskell, Wichita-Brazos and California Creek Soil and Water Conservation districts, the U.S. Department of Agriculture-Natural Resources Conservation Service, Texas AgriLife Extension Service, Texas A&M AgriLife's Texas Water Resources Institute, Rolling Plains Groundwater Conservation District and AgriLife Research.
"We don't know what percentage of the nitrate is geologic in nature or what percentage is due to farming operations," Sij said. "But if we take it into consideration in our fertility programs, we can mine the nitrogen and use it as a resource."
Mining the water for nitrates, instead of putting in additional and sometimes unnecessary nitrogen, may also have the potential to improve water quality from the Seymour Aquifer, he said.
Ninety percent of the water from the Seymour in Knox, Haskell, Baylor, Wichita, Wilbarger and Fisher counties is used for irrigation, he said. For those agricultural producers, it could be a source of nutrients that could reduce fertiliser costs.
"We encourage the installation of subsurface drip irrigation systems where possible," Sij said. This is thought to improve the water quality by reducing the nitrates, and to allow producers to realise the benefits of those nutrients supplied in the irrigation water.
Assuming a 20 parts per million nitrate concentration and just 12 inches of applied irrigation water per acre over the growing season, approximately 55 pounds of useable nitrogen per acre can be applied to a cotton crop, DeLaune said.
This amount of nitrogen exceeds the 50-pound requirement for a bale of cotton, Sij said. With drip irrigation, it can be put into the soil around the roots and not lost through denitrification as might occur through surface application of nitrogen.
Drip irrigation is a very efficient delivery system for nutrients, he said.
"At nearly a $1 per pound for fertiliser nitrogen these days, 55 'free' pounds of nitrogen can add up to significant cost savings, about $55 per acre or more, for producers who irrigate their crops with high nitrate ground water," DeLaune said.
The 150 pounds of nitrogen needed to grow three-bale cotton can be reduced if producers learn to take into account what is already in the soil and, now, what is in the water, he said.
"They need to know both those numbers before planning their fertiliser program," Sij said.
Of course, other nutrients like potassium and phosphorous must be adequate to take advantage of nitrates in the irrigation water as well as any applied fertiliser nitrogen, he said.
Producers should have their irrigation water analysed for nitrate annually and make allowance for this free nitrogen source when determining crop fertiliser needs, Sij said.
Drought Management and Agriculture in British Columbia
The past few years have seen some of the driest and hottest years on record in British Columiba, a scenario that is likely going to repeat itself as the 21st century progresses.
We often think about how drought may impact community water supplies, recreation and other activities.
What about the security of our food supply ?
Drought can have a major impact on agricultural production. Impacts are not only felt for the current drought year, but can have lingering impacts that last several years.
Producers that are forced to sell their herds because of a shortage of feed supply cannot just replenish the herd numbers quickly in subsequent years. Similarly, if perennial plants die due to a lack of water, it takes years to establish anew plant that will achieve the same level of production.
The Ministry of Agriculture and Lands has developed a series of factsheets that provide producers with useful information on how to manage droughts and reduce the effects of droughts.
The province has also developed a drought response plan. The components of the plan and other relevant information are explained in the following powerpoint presentation link:
Environmental water management
The National Water Initiative recognises the integrated management of environmental water as a key area of importance. The National Water Initiative requires effective and efficient management and institutional arrangements to be in place to ensure the achievement of environmental outcomes. This includes:
- the establishment of accountable and well resourced environmental water managers who have the ability to participate in water markets
- the trading of water and utilisation of market based mechanisms for the recovery of water for environmental outcomes
- an agreement to give statutory recognition to, and at least the same level of security as other water access entitlements, to environmental water
While the current arrangements under the National Water Initiative have made substantial contributions to water management, current progress suggests that the objectives of the National Water Initiative are unlikely to be met without a significant intervention.
If over-allocation and over-use in the Murray-Darling Basin are not addressed now river health, the environment and other public amenity values will be severely impacted.
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