Baffling Marine Geology DiscovERIES

In July 1950 a group of scientists studying the sea-floor of the Pacific ocean made surprising discoveries that influenced the formulation of Hess's developing ideas about the origin and evolution of ocean basins. scientists believed that the oceanic crust was mostly flat and extremely thick owing to the accumulation of billions of years of sediment from continental erosion. Using explosives and seismic waves, the crew determined the thickness of the oceanic crust to be about four miles (7 km)....

The History Of Life And Mass ExTinctions

Life on Earth has evolved from simple prokaryotic organisms such as Archaea that appeared on Earth by 3.85 billion years ago. Life may have been here earlier, but the record is not preserved, and the method by which life first appeared is also unknown and the subject of much thought and research by scientists, philosophers, and religious scholars. The ancient Archaea derived energy from breaking down chemical bonds of carbon dioxide, water, and nitrogen, and anaerobic archaeans have survived to...

Tsunami nightmare

One of the worst natural disasters of the 21st century unfolded on December 26, 2004, following a magnitude 9.0 earthquake off the coast of northern Sumatra in the Indian Ocean. The earthquake was the largest since the 1964 magnitude 9.2 event in southern Alaska and released more energy than all the earthquakes on the planet in the last 25 years combined. During this catastrophic earthquake, a segment of the seafloor the size of the state of California, lying above the Sumatra subduction zone...

On river dynamics

The long history of flooding and attempted flood-control measures along the Mississippi River basin had taught engineers valuable lessons on how to manage flood control on river basins. Levees are commonly built along riverbanks to protect towns and farmlands from river floods. These levees usually succeed at the job they were intended to do, but they also cause other collateral effects. First, the levees do not allow waters to spill onto the floodplains, so the floodplains do not receive the...

Work In The Petroleum Industry

By the end of World War I Holmes had written three books but was still only a demonstrator at Imperial College. In 1918 the Holmeses had their first child, Norman, and a demonstrator's income was not sufficient to support the family. The Yomah Oil Company hired Holmes as chief geologist with the promise of a much larger salary. His family moved to Burma in November 1920 and settled in Yenangyaung, where Holmes spent two years frantically searching for new oil finds to save the struggling...

Russian East European Craton

The Russian or East European craton is well exposed in the Baltic states and in the Ukrainian shield, but it is mostly buried beneath late Precambrian to Pha-nerozoic cover in the Russian craton. The amalgamated East European craton, which formed the core of the Baltica block in the Proterozoic supercontinents of Rodinia and Gondwana, consisted of the Fen-noscandian block (Baltic shield) in the northwest, the Volgo-Uralia block in the east, and the Sarmatia block in the south. The Baltic shield...

Geothermal Energy In Regions With Geysers

Geysers, hot springs, and fumaroles are associated with regions of elevated temperature at depth, and in some cases these high temperatures have been exploited for geothermal energy. Temperatures in the Earth generally increase downward at 90 -250 F (30 -140 C) per mile (68-212 F 20 -100 C per km), following the geothermal gradient for the region. some regions near active volcanic vents and deep-seated plutons have even higher geothermal gradients and are typified by abundant fumaroles and hot...

Types Of Surface Subsidence And Collapse

Some subsidence occurs because of processes that happen at depths of thousands of feet beneath the surface, and is referred to as deep subsidence. Other subsidence is caused by shallow near-surface pro cesses and is known as shallow subsidence. Tectonic subsidence is a result of the movement of the plates on a lithospheric scale, whereas human-induced subsidence refers to cases where the activities of people, such as extraction of fluids from depth, have resulted in lowering of the land...

Climate and Seasonality

Variations in the average weather at different times of the year are known as seasons, controlled by the average amount of solar radiation received at the surface in a specific place for a certain time. several factors determine the amount of radiation received at a particular point on the surface, including the angle at which the sun's rays hit the surface, the length of time the rays warm the surface, and the distance to the sun. As the Earth orbits the sun approximately once every 365 days,...

Oort Cloud

The oort Cloud is a roughly spherical region containing many comets and other objects, extending from about 60 A.u. to beyond 50,000 A.u., or about 1,000 times the distance from the sun to Pluto, or about one light year. This distance of the outer edge of the solar system is also about one quarter of the way to the closest star neighbor, Proxima Centauri. The oort Cloud is thought to be the source for long- period comets and Halley-type comets that enter the inner solar system. It contains...

Cenozoic Tectonics And Climate

Cenozoic global tectonic patterns are dominated by the opening of the Atlantic Ocean, closure of the Tethys Ocean, and formation of the Alpine-Himalayan Mountain System, and mountain building along the western North American cordillera. Uplift of mountains and plateaus and the movement of continents severely changed oceanic and atmospheric circulation patterns, changing global climate patterns. As the North and South Atlantic Oceans opened in the Cretaceous, western North America was...

Valdez Alaska 1964 magnitude

One of the largest earthquakes ever recorded struck southern Alaska at 5 36 p.m. on March 27, 1964, second in the amount of energy released only to the 1960 Chile earthquake. The energy released during the Valdez earthquake was more than the world's largest nuclear explosion and greater than the Earth's total average annual release of seismic energy, yet, remarkably, only 131 people died during this event. Damage is estimated at 240 million (1964 dollars), a remarkably small figure for an...

Solidification Of magma

Just as rocks partially melt to form different liquid compositions, magmas can solidify to different minerals at different times to form different solids (rocks). This process also results in the continuous change in the composition of the magma if one mineral is removed, the resulting composition is different. If some process removes these solidified crystals from the system of melts, a new magma composition results. Several processes can remove crystals from the melt system, including...

Admired And Honored

Beginning in 1962 Hess chaired the Space Science Advisory Board of the National Academy of Sciences. The board's responsibility was to advise NASA. In 1966 he was at Woods Hole, Massachusetts, chairing a meeting to discuss the scientific objectives of lunar exploration when he began having chest pains. He died of a heart attack on August 25, 1969, and was buried at the Arlington National Cemetery. Hess was elected to membership of several academic societies including the National Academy of...

San Francisco 1906 magnitude

Perhaps the most infamous earthquake of all time is the magnitude 7.8 temblor that shook San Francisco at 5 12 a.m. on April 18, 1906, virtually destroying the city, crushing 315 people to death and killing 700 people throughout the region. Many of the unrein-forced masonry buildings that were common in San Francisco immediately collapsed, but most steel and wooden frame structures remained upright. Ground shaking and destruction were most intense where structures were built on areas filled in...

Principles And Elements

Geologists of the time were prepared to reject Werner's ideas for Hutton's, but they needed a push. They were ready to accept that basalt was of igneous origin but more hesitant to accept uniformity of geological processes of the past and the present and of uniform gradual rates of change. Lyell published Principles of Geology An Attempt to Explain the Former Changes in the Earth's Surface by Reference to Causes Now in Operation, which appeared in three volumes between 1830 and 1833 and is now...

Final Years

Having accomplished his two career goals of dating the Earth and constructing a geological timescale that could be applied to common rocks, Holmes concentrated on his professorial duties. In 1943 the university of Edinburgh appointed him regius professor of geology, a position subsidized by the king of England. The outbreak of World War II forced Holmes to reduce his geology course from one year to six months. Though it would have saved lecture time to assign students reading material before...

Timelines And Diachronous Boundaries

In many sedimentary systems, such as the continental shelf, slope, and rise, different types of sediments are deposited in different places at the same time. We can draw time lines through these sequences to represent all the sediments deposited at a given time or to represent the old sediment water interference at a given time. In these types of systems, the transition from one rock type to another, such as from the sandy delta front to the marsh facies, will be diachronous in time (it will...

Coastal Lagoons

Lagoons are a special, rather rare class of restricted coastal bays that are separated from the ocean by an efficient barrier that blocks any tidal influx, and they do not have significant freshwater influx from the mainland. Water enters lagoons mainly from rainfall and occasional storm wash-over. Evaporation from the lagoon causes their waters to have elevated salinity and distinctive environments and biota. most lagoons are elongate parallel to the coast and separated from the ocean by a...

Hazards of Volcanicinduced Earthquakes and Tsunamis

Minor earthquakes generally accompany volcanic eruptions. The earthquakes are generated by magma forcing its way upward through cracks and fissures into the volcano from the magma chamber at depth. Gas explosions in the magma conduits under the volcano generate other earthquakes. The collapse of large blocks of rock into calderas or the shifting of mass in the volcano may also initiate earthquakes. some of these earthquakes happen with a regular frequency, or time between individual shocks, and...

Pakistan October 8 2005 magnitude

At 8 50 a.m. on saturday, october 8, 2005, remote areas of northern Pakistan, north of Islamabad and neighboring Afghanistan, were hit by a major earthquake that caused catastrophic damage to a wide area, largely because of the inferior construction of buildings throughout the region. This earthquake killed more than 86,000 people and injured more than 69,000, leaving about 4 million homeless as the freezing cold of the Kashmir winter set in to the mountainous region. Worst hit was the...

Intertidal Flats

Many coastlines have flat areas within the tidal range sheltered from waves, dominated by mud, and devoid of vegetation that are accumulating sediment, known as intertidal (or just tidal) flats. The width of tidal flats depends on the tidal range and the shape and morphology of the coastline or bay where they are located. some large bays with large tidal ranges, such as the Bay of Fundy in eastern Canada, are dominated by tidal flats. Tidal flats are typically flat areas cut by many channels...

Baltic Shield

The Baltic (Fennoscandian) shield is an Archean cra-ton divided into three distinct parts. The northern, Lapland-Kola province consists mainly of several previously dispersed Archean crustal terranes that together with the different Paleoproterozoic belts have been involved in a collisional-type orogeny at 2.0 to 1.9 billion years ago. A central, northwest-trending segment known as the Belomorian mobile belt is occupied by assemblages of gneisses and amphibo-lites. This part of the Baltic...

Summary

Modern classification schemes for the composition of asteroids and meteorites divide them into either chondrites or nonchondrites. The nonchondrites are divided into primitive and differentiated types. The differentiated nonchondrites have three groups, including the achondrites, stony-irons, and irons, based on the chemistry and texture of the meteorites and reflecting their origin. Chondrites have compositions similar to the sun, and represent the average composition of the solar system,...

Andes

Rio Plata Craton

The Andean mountain chain is a 5,000-mile- (8,000km-) long belt of deformed igneous, metamorphic, and sedimentary rocks in western south America, running generally parallel to the coast, between the Caribbean coast of Venezuela in the north and Tierra del Fuego in the south. some sections are characterized by active volcanoes, others by their absence. Most of the Andes are located above the subducting Nazca plate except for the southern Andes, which are located above the subducting Antarctic...

Chilimanzi Suite

The Chilimanzi suite of K-rich granitoids is one of the last magmatic events in the Zimbabwe craton, with reported ages of 2.57 to 2.6 billion years. These granites appear to be associated with a system of large intracontinental shear zones that probably controlled their position and style of intrusion. These relatively late structures are related to north-northwest to south-southeast shortening and associated southwestward extrusion of crust during the continental accretion and collision as...

Core Contraction And Hydrogen Shell Burning

As the helium in the core builds up it cannot burn, since it requires much higher temperatures to fuse than does hydrogen. The result is that when the hydrogen is used up, the core contracts, since the gas pressure without high temperatures from nuclear fusion is not sufficient to counteract the force of gravity. The shrinkage of the core then releases gravitational potential energy that creates heat, raising the temperature of the core. As the core grows increasingly hot in this way (but not...

Interstellar Cloud

Stars that are close to a solar mass start their evolution as an ordinary, dense, and cold interstellar cloud that may be tens of parsecs across (1 parsec equals 3.3 light years), having temperatures of about 10 K, and densities of around 109 particles per cubic meter. The amount of mass in these types of interstellar clouds may be thousands or millions of times a solar mass at this stage. Typical giant molecular clouds that collapse to form solar-type stars are 6,000,000 solar masses and 100...

Transform Boundaries In The Oceans

Transform plate boundaries in the oceans include the system of ridge-ridge transform faults that are an integral part of the mid-ocean ridge system. Magma upwells along the ridge segments, cools and crystallizes, becoming part of one of the diverging plates. The two plates then slide past each other along the transform fault between the two ridge segments, until the plate on one side of the transform meets the ridge on the other side of the transform. At this point, the transform fault is...

Drying Of The American Southwest

A drought is a prolonged lack of rainfall in a region that typically experiences a significant amount of precipitation. If a desert normally receives a small amount of rainfall, and it still is getting little rainfall, then it is not experiencing a drought. In contrast, a different area that normally receives more rainfall than the desert may be experiencing a drought if it normally receives significantly more rainfall than it is at present, even if it still experiences more rainfall than the...

Jet Streams

Jet streams are high-level, narrow, fast-moving currents of air typically thousands of kilometers long, hundreds of kilometers wide, and a couple of miles (several kilometers) deep. Jet streams typically form near the tropopause, six to nine miles (10-15 km) above the surface, and can reach speeds of 115-230 miles per hour (100-200 knots). Rapidly moving cirrus clouds often reveal the westerly jet streams moving air from west to east. several jet streams are common the subtropical jet stream...

Landslideinduced Tsunamis of the Canary Islands Atlantic Ocean

The Canary Islands form a hot-spot chain of small rugged volcanic islands off the northwest coast of Africa. They constitute two provinces of Spain, Santa Cruz de Tenerife and Las Palmas. The high est point on the islands is Mt. Teide on Tenerife at 12,162 feet (3,709 m) above sea level, although the volcanoes actually rise more than 10,000-13,000 feet (3,000-4,000 m) from the seafloor before the rise above sea level. The Canary Islands are hotspot type shield volcanoes, very similar to Hawaii,...

Polar

Polar lows are hurricane- or gale-strength storms that form over water behind (poleward) the main polar front. They can form over either the Northern or Southern Hemisphere oceans but are a larger menace to the more populated regions around the North Atlantic, North Sea, and Pacific Ocean, as well as the Arctic Ocean. Most polar lows are much smaller than tropical and midlatitude cyclones, with diameters typically fewer than 600 miles (1,000 km). Like hurricanes, many polar lows have spiral...

Types Of Island And Convergent Margin Arcs

There are major differences in processes that occur at continental or Andean-style versus oceanic or island arc systems, also known as Marianas-type arcs. Andean-type arcs have shallow trenches, fewer than four miles (6 km) deep, whereas marianas-type arcs typically have deep trenches reaching seven miles (11 km) in depth. most Andean-type arcs subduct young oceanic crust and have very shallow-dipping subduction zones, whereas Marianas-type arcs subduct old oceanic crust and have steeply...

Kinds Of Metamorphism

Metamorphism is a combination of chemical reactions induced by changing pressure and temperature conditions and mechanical deformation caused by differential stresses. The relative importance of physical and chemical processes changes with meta-morphism in different tectonic settings. Near large plutons or hot igneous intrusions, rocks are heated to high temperatures without extensive mechanical deformation. These elevated temperatures cause rocks next to plutons to grow new minerals, but these...

Kalaharicraton

Southern Africa's Kalahari craton is composed of two older cratons, the Kaapvaal and Zimbabwe, that collided and were sutured 2.5 billion years ago along the Limpopo belt and have acted as a single craton since that time. For times before 2.5 billion years ago, therefore, the two parts (Kaapvaal and Zimbabwe cratons) are discussed separately, but from True-color composite satellite image of Africa from data collected by the Thematic Mapper instrument on an American Landsat satellite. The Sahara...

Physical Properties Of The

The Sun contains no solid material, but the apparent surface visible as a glowing solar disk is known as the photosphere. Above the photosphere is the Sun's lower atmosphere, called the chromosphere, and extending far past that is the corona, an outer atmosphere (visible during eclipses) that gradually merges into the solar wind and consists of particles that flow through the whole solar system. Extending below the photosphere toward the deep interior of the Sun are three more main zones. The...

Causes Of Shortterm Climate Change

The IPCC issued new reports, Climate Change 2007, in 2007 revealing that concentrations of some greenhouse gases have increased dramatically as a result of human activities, mostly starting with the early industrial revolution around 1750 and accelerating in the late industrial revolution around 1850. The greenhouse gases that show the most significant increases are carbon dioxide, methane, and nitrous oxide. Carbon dioxide (C02), the most significant anthropogenic greenhouse gas, is produced...

Kinetic Impact Strategies

One of the alternative strategies that may be effective in deflecting an asteroid from Earth's orbit is to send a massive spacecraft to collide with the asteroid, altering its momentum and removing it from the collision course. This strategy is currently the object of a major study and mission, called Don Quijote, by the European Space Agency. Early results from this mission have shown that it is possible, and a model of the deflection of near-Earth asteroid 99942 Apophis shows that it would...

Desert Landforms

Desert landforms are some of the most beautiful on Earth, often presenting bizarre sculpted mountains, steep walled canyons, and regional gravel plains. They can also be some of the most hazardous landscapes on the planet. The regolith, or mixture of soil and altered bedrock in deserts is thin, discontinuous, and much coarser-grained than in moist regions, and is produced predominantly by mechanical weathering. Chemical weathering is only of minor importance because of the rare moisture. Also...

Pacific Plate Subduction

Subduction along the Pacific margin of China was active from 200 to 100 Ma, soon after closure of the ocean basins on the northern side of the North China craton. Westward-directed oblique subduction was responsible for the generation of arc magmas, deformation, and possibly mantle hydration during this interval. Although the duration and history of Mesozoic subduction beneath the eastern margin of China is not well known, the active margin stepped outward by the Cenozoic, from which a better...

Survey Of Impact Craters On Earth And The Moon

Impact craters are known from every continent including Antarctica. Several hundred impact craters have been mapped and described in detail by geologists, and some patterns about the morphology, shape, and size of the craters have emerged from these studies. The most obvious variations in crater style and size are related to the size of the impacting meteorite, but other variations depend on the nature of the bedrock or cover, the angle and speed of the impact, and what the impactor was rock or...

Silica and Coal Dust

Other minerals can be hazardous if made into small airborne particles that can lodge in the lungs. As with asbestos, both silica- and coal-mining operations release large amounts of dust particles into the air, also known, respectively, as quartz dust and coal dust. Workers exposed to these dusts are at risk for diseases broadly similar to asbestosis. Quartz dust is commonly produced during rock drilling and sandblasting operations. These practices produce airborne particles of various sizes,...

Cretaceous Volcanics And The Marion Hot Spot

On the southern side of the island of Madagascar, the shallow-water Madagascar plateau extends 500 miles (800 km) south along the Marion hot spot track to Marion Island. The volcanics associated with this hot spot track correlate with the Late Cretaceous (90 Ma) volcanics abundant on the island, associated with the separation of Madagascar from the Seychelles and India. They become younger progressively to the south to zero-age volcanic on Marion Island. Madagascar was most likely flat and near...

Rainshadow Deserts

A third type of desert is found on the leeward, or back, side of some large mountain ranges, such as the sub-Andean Patagonian Gran Chaco and Pampas of Argentina, Paraguay, and Bolivia. A similar effect is partly responsible for the formation of the Mojave and Sonoran Deserts of the United States. These deserts form because as moist air masses move toward the mountain ranges, they must rise to move over the ranges. As the air rises it cools, and cold air cannot hold as much moisture as warm...

Vredefort Impact Structure South Africa

The Vredefort dome of South Africa is one of the world's largest and oldest known, well-preserved impact structures. Located in the late Archean Wit-watersrand basin, the Vredefort dome is a large, multiring structure with a diameter of 87 miles (140 km) formed by the impact of a meteorite 1.97 billion years ago. The geology and structure of the Vredefort dome is complex, and its origin was the subject of debates for many years. The crater is characterized by a series of concentric rims of rock...

Further Reading

Theory of the Earth. Oxford Blackwell Scientific Publications, 1989. Kious, Jacquelyne, and Robert I. Tilling. U.S. Geological Survey. This Dynamic Earth The Story of Plate Tectonics. Available online. URL http pubs.usgs. gov gip dynamic dynamic.html. Last modified March 27, 2007. Moores, Eldridge M., and Robert Twiss. Tectonics. New York W. H. Freeman, 1995. Map of Hawaii-Emperor chain formed by a hot spot track as the Pacific plate moved over a mantle plume. The youngest...

Can Desalination Help SolvE The Water Crisis

With the hydrologie cycle changing through climate change and increased water use, it is important to find new sources of water. Desalination includes a group of water-treatment processes that remove salt from water it is becoming increasingly more important as freshwater supplies dwindle and population grows, yet desalination is exorbitantly expensive and cannot be afforded by many countries. A number of different processes can accomplish desalination of salty water, whether it comes from the...

Gravity anomalies potential Field Studies

Gravity anomalies are the difference between the observed value of gravity at a point and the theoretically calculated value of gravity at that point, based on a simple gravity model. The value of gravity at a point reflects the distribution of mass and rock units at depth, as well as topography. The average gravitational attraction on the surface is 32 feet per second squared (9.8 m s2), with one gravity unit (g. u.) being equivalent to one ten-millionth of this value. Another older unit of...

Solar Core

The energy from the Sun comes from nuclear reactions in its core, generating a luminosity of 4 x 1026 W, or 2 x 104 W kg. The Sun has been producing approximately this vast amount of energy for the past 4.5 billion years. For the entire lifetime of the Sun, the total amount of energy generated has been 3 x 1013 joule kg. The generation of this energy has been remarkably steady and is expected to continue for another 5 billion years, through the process of nuclear fusion. Fusion works by...

South China Craton

The South China craton is divided into the Yangtze craton and the Cathaysia block, joined together in a plate collision in the late Mesoproterozoic. Radio-metric dating of two ophiolite suites in the eastern part of the suture between the Yangtze and Cathay-sia blocks gives ages of 1.03 to 1.02 billion years for the age of this collision. Late Mesoproterozoic suture zones have been also reported from the northwestern and northern margins of the Yangtze block. An ophi-olitic m lange in western...

Siberian Traps

A large part of the central Siberian plateau northwest of Lake Baikal is covered by a thick series of mafic volcanic flows. They are more than half a mile thick (1 km) over an area of 210,000 square miles (543,900 km2) but have been significantly eroded from an estimated volume of 1,240,000 cubic miles (5,168,545 km3). This extraordinary sequence of lavas was erupted over a remarkably short period of less than 1 million years, 250 million years ago, at the Permian-Triassic boundary. Within the...

Hurricane Andrew 1992

Hurricane Andrew was the second-most destructive hurricane in U.S. history, causing more than 30 billion in damage in August 1992. Andrew began to form over North Africa and grew in strength as trade winds drove it across the Atlantic. On August 22 Andrew had grown to hurricane strength and moved across the Bahamas with 150-mile-per-hour (241 km hr) winds, killing four people. On August 24 Andrew smashed into southern Florida with a nearly 17-foot (5.2-m) high storm surge, steady winds of 145...

Grenville belts and the rodinia supercontinent

The Proterozoic saw the development of many continental-scale orogenic belts, many of which have been recently recognized to be parts of global-scale systems that reflect the formation, breakup, and reassembly of several supercontinents. Paleoproterozoic orogens include the Wopmay in northern Canada, interpreted to be a continental margin arc that rifted from North America, then collided soon afterward, closing the young back arc basin. There are many 1.9-1.6-Ga orogens in many parts of the...

Lematre Georges 18941966 Belgian

Cosmologist Georges Lema tre is most famous for proposing the theory of the big bang in 1933. He was born July 17, 1894, in Charleroi, Belgium, where he studied civil engineering and obtained a Ph.D. for his dissertation, L'Approximation des fonctions de plusieurs variables r elles (Approximation of functions of several real variables). He was ordained in 1923 as a Catholic priest before moving to Cambridge, United Kingdom, to study astrophysics at St. Edmund's College. He then moved to the...

Juvenile island arc accretion

Many Archean granite-greenstone terranes are interpreted as juvenile island arc sequences that grew above subduction zones and later amalgamated during collisional orogenesis to form new continental crust. The island arc model for the origin of the continental crust is supported by geochemical studies that show the crust has a bulk composition similar to arcs. Island arcs are extremely complex systems that may exhibit episodes of distinctly different tectonics, including accretion of ophiolite...

Coastal Deserts

Some deserts are located along coastlines, where intuition would seem to indicate that moisture should be plentiful. The driest place on Earth is the Atacama Desert, however, located along the coast of Peru and Chile. The Namib Desert of southern Africa is another coastal desert, known legendarily as the skeleton Coast, because it is so dry that many of the large animals that roam out of the more humid interior climate zones perish there, leaving their bones sticking out of the blowing sands....

Dynamics Of Stream Flow

Streams are dynamic systems and constantly change their channel patterns and the amount of water (discharge) and sediment being transported in the system. streams may transport orders of magnitude more water and sediment in times of spring floods, as compared with low-flow times of winter or drought. since streams are dynamic systems, as the amount of water flowing through the channel changes, the channel responds by changing its size and shape to accommodate the extra flow. For instance, in a...

Northern Hemisphere snow cover

Graphs of global average temperature, sea level, and snow cover for the past 160 years (Data from IPCC 2007) Spruce killed by spruce bark beetle near Homer, Alaska (Peter Essick Aurora Getty Images) Spruce killed by spruce bark beetle near Homer, Alaska (Peter Essick Aurora Getty Images) Northern and the Southern Hemispheres. Changes in the ice caps on Greenland and Antarctica show an increased outflow of glacial ice and meltwater, so melting of the polar ice caps is very likely contributing to...

The Hydrologic Cycle

The water cycle describes the sum of processes operative in the hydrosphere, a dynamic mass of liquid continuously on the move between the different reservoirs on land and in the oceans and atmosphere. The hydrosphere includes all the water in oceans, lakes, streams, glaciers, atmosphere, and groundwa-ter, although most water is in the oceans. The hydro-logic, or water, cycle encompasses all of the changes, both long- and short-term, in the Earth's hydrosphere. It is powered by heat from the...

Beauty And The Beach Rethinking Coastal Living

Civilized societies have built villages, cities, and industrial sites near the sea for thousands of years. Coastal settings offer beauty and commercial convenience but also invite disaster with coastal storms, tsunami, and rising sea levels. In 2004 and 2005 the world witnessed two furious incursions of the sea into heavily populated coastal regions, killing hundreds of thousands of people and causing trillions of dollars in damage. Coastal communities are experiencing early stages of a new...

Radon

Radon is a poisonous gas released during radioactive decay of the uranium decay series. Radon is a heavy gas, and it presents a serious indoor hazard in every part of the country because it accumulates in poorly ventilated basements and well-insulated homes that are built on specific types of soil or bedrock rich in uranium minerals. Radon causes lung cancer, and since it is an odorless, colorless gas, its presence can go unnoticed in homes for years. However, the hazard of radon is easily...

Emission Nebulae

The sections above focused on the formation of stars from the collapse of interstellar dust clouds but did not focus on the effects these processes have on the surrounding intergalactic medium. Star formation as described above does not usually result in the formation of just one star, but rather a group or cluster of stars with similar characteristics and ages in a region that represents the original collapsed interstellar cloud. The more massive the original collapsed dust cloud, the more new...

Flash Floods

Flash floods result from short periods of heavy rainfall and are common near warm oceans, along steep mountain fronts in the path of moist winds, and in areas prone to thunderstorms. They are well known from the mountain and canyon lands of the U.S. desert Southwest and many other parts of the world. Some of the heaviest rainfalls in the United States have occurred along the Balcones escarpment in Texas. Atmospheric instability in this area often forms along the boundary between dry desert air...

Namib desert and the skeleton coast

Namibia's Atlantic coastline is known as the skeleton coast, named for the suffering and death that beset many sailors attempting to navigate the difficult waters swept by the cold Benguela current, which moves along the coast, and warm winds coming off the Namib and Kalahari Deserts. The coastline is littered with numerous shipwrecks, testifying to the difficult and often unpredictable nature of shifting winds and ocean currents. Giant sand dunes of the Namib sand sea reach to the coast, and...

Mount St Helens 1980 and the Cascades Today

The most significant eruption in the contiguous united states in the past 90 years is that of Mount st. Helens in 1980, a mountain that had lain dormant for 123 years. The volcano is part of the active Cascade volcanic arc, a continental-margin arc built on the western coast of North America above where the minor Juan de Fuca plate is being subducted beneath North America. The arc is relatively small (about 1,200 miles, or 2,000 km, long), and stretches from Lassen Peak in California to Mount...

Rapid Changes In Ocean Circulation Patterns And Cumate Change

Some models of climate change show that patterns of ocean circulation can suddenly change and cause global climate conditions to switch from warm to cold, or cold to warm, over periods of a few decades. Understanding how fast climate can shift from a warm period to a cold, or cold to a warm, is controversial. The record of climate indicators is incomplete and difficult to interpret. Only 18,000 years ago the planet was in the midst of a major glacial interval, and since then global average...

Glaciation And Glacial Landforms

Glaciation is the modification of the land's surface by the action of glacial ice. When glaciers move over the land's surface, they plow up the soils, abrade and file down the bedrock, carry and transport the sedimentary load, steepen valleys, then leave thick deposits of glacial debris during retreat. In glaciated mountains a distinctive suite of landforms results from glacial action. Glacial stria- tions are scratches on the surface of bedrock, formed when a glacier drags boulders across the...

Darwins Theory Of EvOLUTION

When Darwin returned to London he was already a celebrity in some scientific circles, since his mentor Henslow had shared many of his geological notes and biological findings with colleagues. After visiting family and friends Darwin returned to Cambridge and studied his notes, data, and samples with the help of many colleagues and scientists recommended by Henslow. Together they cataloged his collections from around the world and discussed many of the possibilities suggested by his geological...

Glossopetrae

While waiting for these results to be published in the fall of 1666, an enormous great white shark that weighed about 2,800 pounds (1,270 kg) was captured and killed on a beach off Livorno. Ferdinando asked Steno to dissect its head, which was brought to Florence. Before a large audience, Steno carefully dissected away the skin and soft tissues and examined the nerves and the tiny brain. The excitement at the scene must have been incredible. The beast's teeth were almost three inches (7.6 cm)...

Structural geology And Plate Tectonics

The surface of the Earth is divided into 12 major and several minor plates that are in motion with respect to each other. Plate tectonics describes these relative motions, which are, to a first approximation, rigid body rotations. However, deformation of the plates does occur (primarily in belts tens to hundreds of kilometers in width along the plate boundaries), and in a few places, extends into the plate interiors. structural geology deals with these deformations, Hypsometric curve showing...

Wind In Deserts

Wind plays a significant role in the evolution of desert landscapes. Wind erodes in two basic ways. Deflation is a process whereby wind removes material from an area, reducing the land surface. The process is akin to deflating a balloon below the surface of the ground, hence its name. Abrasion is a different process that occurs when particles of sand and other size grains are blown by the wind and impact one another. Exposed surfaces in deserts are subjected to frequent abrasion, which is...

The Greenhouse Effect

The term greenhouse effect refers to the Earth's climate as being sensitive to the concentrations of certain gases in the atmosphere. The concept was first coined by French physicist Edme Mariotte (1620-84) in 1681, who noted that light and heat from the Sun easily pass through a sheet of glass, but that heat from candles and other sources does not. This concept was then extended by French mathematician and physicist Joseph Fourier in 1824 to the atmosphere by noting that heat and light from...

Krakatau Indonesia 1883

Indonesia has seen catastrophic volcanic eruptions and associated tsunamis other than from Tambora. The island nation of Indonesia has more volcanoes than any other country in the world, with more than 130 known active volcanoes. These volcanoes have been responsible for about one-third of all the deaths attributed to volcanic eruptions and associated tsunamis in the world. Indonesia stretches for more than 3,000 miles (5,000 km) between southeast Asia and Australia, is characterized by very...

American Desert Southwest

The history of development the American desert southwest was crucially dependent on bringing water resources into this semiarid region. much of California, especially the Los Angeles region, was regarded as worthless desert scrubland until huge water projects designed by the Bureau of Land Reclamation diverted rivers and resources from all over the West. In the years between 1911 and 1923 the California water department under the leadership of William Mulholland quietly purchased most of the...

Major volcanic Eruptions and Climate Change

Some of the larger, more explosive volcanic eruptions that the planet has witnessed in the past few hundred years have ejected large amounts of ash and finer particles called aerosols into the atmosphere and stratosphere, and it may take years for these particles to settle down to Earth. They get distributed about the planet by high-level winds, and they block some of the Sun's rays, which lowers global temperatures. This happens because particles and aerosol gases in the upper atmosphere tend...

Evolution in the fossil record

The vast expanses of time needed to test models of evolution are provided by the fossil record, which extends back hundreds of millions of years for complex organisms, and billions of years for simple organisms. The first example of evolution described from the geologic record was in 1869, when German geologist Wilhelm Heinrich Waagen (1841-1900), who studied Jurassic ammonites, published his classic Die Formenreihe des Ammonites subradiatus (The Sequence of Form of the Ammonite's...

Physical Properties Of GalaxIES

The observable universe presents an estimated minimum of 100 billion galaxies, and many of these have billions of stars in them. Most of these galaxies are located far from Earth and the Milky Way Galaxy, and thus are difficult to observe closely. To measure distances to and sizes of these distant galaxies one must use some objects, such as planetary nebulae or certain kinds of supernovae that have known brightnesses, and then use their apparent brightness to measure their distance from Earth....

Siberian Taiga Forest And Global Carbon Sink

The northern third of Asia, stretching from the Ural Mountains in the west to the Pacific coast into the east, is known as siberia. The southern border of Siberia is generally taken to be the Kazakh steppes in the southwest, the Altai and sayan Mountains in the south, and the Mongolian steppes in the southeast. This region occupies approximately 3,000,000 square miles (7,500,000 km2). The western third of Siberia is occupied by the Siberian lowland, stretching from the Urals to the Yenisei...

Groundwater Dissolution

Groundwater also reacts chemically with the surrounding rocks it may deposit minerals and cement together grains, causing a reduction in porosity and permeability, or form features like stalagtites and stalagmites in caves. In other cases, particularly when acidic water moves through limestone, it can dissolve the rock, forming caves and underground tunnels. sinkholes form where these dissolution cavities intersect the surface of the Earth. Groundwater dissolution leads to the development of a...

Ophiolite accretion

Ophiolites are a distinctive association of allochtho-nous rocks interpreted to form in a variety of plate tectonic settings such as oceanic spreading centers, back arc basins, forearcs, arcs, and other extensional magmatic settings including those in association with plumes. A complete ophiolite grades downward from pelagic sediments into a mafic volcanic complex generally made of mostly pillow basalts, underlain by a sheeted dike complex. These are underlain by gab-bros exhibiting cumulus...

Atmospheric evolution

Considerable uncertainty exists about the origin and composition of the Earth's earliest atmosphere. Many models assume that methane and ammonia dominated the planet's early atmosphere, instead of nitrogen and carbon dioxide, as it is presently. The gases that formed the early atmosphere could have come from outgassing by volcanoes, from extraterrestrial sources (principally cometary impacts), or, most likely, both. Alternatively, comets may have brought organic molecules to Earth. A very large...

Magnetosphere

The magnetosphere encompasses the limits of the Earth's magnetic field, as confined by the interaction of the solar wind with the planet's internal magnetic field. The natural undisturbed state of the Earth's magnetic field is broadly similar to a bar magnet, with magnetic flux lines (of equal magnetic intensity and direction) coming out of the south polar region, and returning back into the north magnetic pole. The solar wind, consisting of supersonic H+ and 4He2+ ions expanding away from the...

Greenstonegneiss Contact Relationships

An important problem in many greenstone belt studies is determining the original structural relationships between greenstone belts and older gneiss terrains. In pre-1990 studies the significance of early thrusting along thin fault zones went unrecognized, leading to a widespread view that many greenstone belts simply rest in depositional contact over older gneisses, or that the older gneisses intruded the greenstone belt. While this may be the case in a few examples, it is difficult to...

Of metallic ore deposits

Most metallic ores form by one of several main processes, including concentration by hydrothermal fluids, crystallization from an igneous magma, meta-morphic processes that move fluids and chemical components in rocks from place to place, weathering, sorting by water in streams, or other surficial processes that can remove some elements from a rock or soil while concentrating other elements. Many of the ores of metallic minerals occur as compounds of the sulfide ion, S2-, with the metals...

Natural Gas and Gas Hydrate Eruptioninduced Tsunamis

The continental shelves and slopes around most continents are the sites of deposition of very thick piles of sediments. River deltas such as the Mississippi delta may add even more sediments to these environments, in some cases forming piles of sediment that are 10 miles (16 km) thick, deposited over many millions of years. Natural gas is produced in submarine sediments by the anaerobic decay of organic matter that becomes buried with the sediments. The gas produced by the decay of these...

Cosmic microwave background radiation

In 1964 two American scientists, Arno Penzias and Robert Wilson, were working on a project at Bell Laboratories in New Jersey to identify and eliminate sources of interference with satellite communications. In their work they accidentally stumbled on one of the most important finds in astronomy and astrophysics of the century. While Penzias and Wilson were examining the radiowave emissions from the Milky Way Galaxy using microwave wavelengths, they discovered a background hiss that would not go...

Plate Tectonics Supercontinents And Life

Plate tectonic motions, especially the supercontinent cycle, profoundly affect the distribution and evolution of life on Earth. Plate tectonic activity such as rifting, continental collision, and drifting continents affects the distribution of life-forms, the formation and destruction of ecological niches, and radiation and extinction blooms. Plate tectonic effects also can induce sea level changes, initiate periods of global glaciation, change the global climate from hothouse to icehouse...

Love Canal Is Not For Honeymooners

Love Canal is not a place many people would choose to visit on a honeymoon. Love Canal was a quiet neighborhood in Niagara Falls, New York, that became infamous as one of the most horrific toxic waste dumps in the country. The history of Love Canal began in the 1890s, when entrepreneur William T. Love envisioned building a canal that would connect the two levels of the Niagara River, above and below the falls, for generating electricity and, eventually, as a shipping canal. He dug about a mile...

Further Resources

Natural Disasters. 3rd ed. Boston McGraw-Hill, 2002. A college freshman-level book about natural disasters, listing causes and examples. Abrahams, A. D., and A. J. Parsons. Geomorphol-ogy of Desert Environments. Norwell, Massachusetts Kluwer Academic Publishers for Chapman and Hall, 1994. This is a comprehensive textbook, describing the wide range of landforms and processes in desert environments. Ahrens, C. D. Meteorology Today, An Introduction to Weather, Climate, and the...

Emergence Of Photosynthesis

The first single-celled organisms were heterotrophs they could not manufacture their own food. These organisms consumed the inorganically formed amino acids or other chemicals existing in their immediate environment. These early organisms received energy from these amino acids by fermentation, the processes of breaking down food molecules (sugars) through a series of chemical steps, into carbon dioxide and alcohol. When photosynthesis began, organisms became able to manufacture their own food...

Continental Interior Midlatitude Deserts

Some places on Earth are so far from ocean moisture sources that by the time weather systems reach them, most of the moisture they carry has already fallen. This effect is worsened if the weather systems must rise over mountains or plateaus to reach these areas, because cloud systems typically lose moisture as they rise over mountains. These remote areas therefore have little chance of receiving significant rainfall. The most significant deserts in this category are the Taklimakan-Gobi region...

Himalaya Mountains

Where Nanga Parbat Located

The Himalaya Mountains were formed during the Tertiary continent-continent collision between India and Asia and contain the tallest mountains, as well as those exhibiting the greatest vertical relief over short distances, in the world. The range extends for more than 1,800 miles (3,000 km) from the Kara-koram near Kabul, Afghanistan, past Lhasa, Tibet, to Arunachal Pradesh in the remote Assam Province of India. Ten of the world's 14 peaks that rise to more than 26,000 feet (8,000 m) are located...

Early Paleozoic History

One of the greatest changes in Earth history is marked by the Precambrian-Phanerozoic transition. At this time the Earth witnessed the first widespread appearance of organisms with hard shells, and there was a huge adaptive radiation unparalleled in the rest of Earth history. By this time most of the cratons on the planet had formed and large continents existed, and plate tectonics had already been through several supercontinent cycles. The history of the early Paleozoic can be interpreted from...

Andesitic Magma

The average composition of the continental crust is andesitic, or somewhere between the composition of basalt and rhyolite. Laboratory experiments show that partial melting of wet oceanic crust yields an andesitic magma. Most andesites today are erupted along continental margin convergent boundaries where a slab of oceanic crust is subducted beneath the continent. Remember that oceanic crust is dry, but after it forms it interacts with seawater, which fills cracks to several miles (kilometers)...

Hadley cell

Hadley cells are the globe-encircling belts of air that rise along the equator and drop moisture as they rise in the Tropics. As the air moves away from the equator at high elevations, it cools, becomes drier, then descends at 15-30 N and S latitude, where it either returns to the equator or moves toward the poles. The locations of the Hadley cells move north and south annually in response to the changing apparent seasonal movement of the Sun. High-pressure systems form where the air descends,...

Volcanic Eruptioninduced Tsunamis

Some of the largest recorded tsunamis have been generated by volcanic eruptions. These may be associated with the collapse of volcanic slopes, debris and ash flows that displace large amounts of water, or submarine eruptions that explosively displace water above the volcano. Approximately 20 percent of volcanic-induced tsunamis form when volcanic ash or pyroclastic flows hit the ocean, displacing large amounts of water, and 20 percent form from earthquakes associated with the eruption. About 15...

Pluton Emplacement Mechanisms

The volume of magma that intruded the Earth's crust in some plutons and batholiths is enormous. All the magma in these plutons had to create space in the crust for it to intrude into, since the plutons typically intrude into preexisting continents. Geologists have long speculated on how such large volumes of magma intrude the crust, and what relationships these magmas have on the style of volcanic eruption. One mechanism that may operate is assimilation, where the magma melts surrounding rocks...

Drainage Systems

A drainage basin is the total area that contributes water to a stream, and the line that divides different drainage basins is known as a divide (such as the continental divide) or interfluve. Drainage basins are the primary landscape units or systems concerned with the collection and movement of water and sediment into streams and river channels. Drainage basins consist of a number of interrelated systems that work together to control the distribution and flow of water within the basin....

Types Of Satellite Imagery

Satellite imagery forms one of the basic tools for remote sensing. The types of satellite images available to the geologist, environmental scientist, and others are expanding rapidly, and only the most common in use are discussed here. The Earth Resources Technology Satellite (ERTS-1), the first unmanned digital imaging satellite, was launched on July 23, 1972. Four other satellites from the same series, later named Landsat, were launched at intervals of a few years. The Landsat spacecraft...