跪求冰川时期的一些英文资料~

跪求冰雹``冰川的一些英文资料~~

glacier:
a slowly moving mass of ice
wordnet.princeton.edu/perl/webwn

A glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. A glacier is formed by multi-year ice accretion in mountainous or sloping terrain. The glacier fringe is the area where the glacier has recently melted. There are two main types of glaciers: alpine glaciers, which are found in mountain terrains, and continental glaciers, which are associated with ice ages and can cover large areas of continents. ...
en.wikipedia.org/wiki/Glacier

Ray Lloyd is a professional wrestler better known as Glacier from his days in World Championship Wrestling.
en.wikipedia.org/wiki/Glacier_(wrestler)

A huge mass of ice, formed on land by the compaction and recrystallization of snow, that moves very slowly downslope or outward due to its own weight.
www.bioquaticsupply.com/html/lkword_g.htm

Bodies of land ice that consist of recrystallized snow accumulated on the surface of the ground, and that move slowly downslope.
www.srh.weather.gov/srh/jetstream/append/glossary_g.htm

a large mass of ice (at least .1km^2) set in motion by the Earth's gravity, which is a result of accumulated snowfall with little snow melt.
www.tsgc.utexas.edu/stars/metgloss.html

A glacier is a slowly-moving river of snow and ice.
www.enchantedlearning.com/explorers/glossary.shtml

A very large body of ice moving slowly down a slope or valley or spreading outward on a land surface
www.climatechangenorth.ca/H1_Glossary.html

A large mass of ice formed by compressed snow, which moves slowly under its own weight. Glaciers exist where, over a period of years, snow remains after summer's end and accumulates year after year.
www.ngdc.noaa.gov/seg/hazard/stratoguide/glossary.html

[glay-sher]- glaciers are accumulations of snow, ice, air pockets, water and rock debris. They can fill valleys or entire continents (as in the case of Antarctica). They have enough mass to flow across a landscape, moving as little as a few feet per year, up to thousands of feet per year. Glaciers are found throughout the world in such places as Africa, New Zealand and Chile.
www.mnh.si.edu/arctic/html/resources_glossary.html

A large mass of ice and snow that forms in areas where the rate of snowfall constantly exceeds the rate at which the snow melts
www.ifdn.com/teacher/glossary.htm

Any field or stream of ice of land origin. It may be either active or stagnant.
www.globalsecurity.org/military/library/policy/army/fm/31-71/Gloss.htm

a large mass of ice formed by the accumulation of falling snow that moves like a river
www.msnucleus.org/membership/html/k-6/rc/dictionary/rcdict.html

a large body of ice with definite lateral limits, which moves in a downslope direction due to its great mass, as in Alaska.
www.dep.state.fl.us/geology/geologictopics/glossary.htm

Accumulation of ice of atmospheric origin generally moving slowly on land over a long period.
www.grid.unep.ch/product/publication/freshwater_europe/glos.php

A mass of land ice, formed by the further recrystallization of firn, flowing continuously from higher to lower elevations. This term covers all such ice accumulations from the extensive continental glacier to tiny snowdrift glaciers. Nearly all glaciers are classified according to the topographical features with which they are associated, for example, highland glacier, plateau glacier, piedmont glacier, valley glacier, cirque glacier. ...
amsglossary.allenpress.com/glossary/browse

A thick mass of ice resulting from compacted snow that forms when more snow accumulates than melts annually.
interactive2.usgs.gov/learningweb/textonly/teachers/volcanoes_guide_glossary.htm

A large mass of snow and ice moving along Earth's surface.
www.mdk12.org/instruction/curriculum/science/glossary.shtml

a body of ice, consisting largely of recrystalized snow, that shows evidence of downslide movement due to its own weight.
www.sd5.k12.mt.us/glaciereft/geogloss.htm

a body of moving ice, usually at least 100 feet thick so that the ice crystals on the bottom deform to effect movement.
www.tc.umn.edu/~smith213/Glossary%20GP.htm

is a body of ice showing evidence of movement as reported by the presence of ice flowline, crevasses, and recent geologic evidence. Glaciers exist where, over a period of years, snow remains after summer's end.
www.ux1.eiu.edu/~cfjps/1300/glacialterms.html

Shown on the map by a white background (ice) and blue contour lines. One glacier is labeled in red, but six other glaciers or partial glaciers also appear on this map. These are all examples of cirque glaciers.
www.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary/more_examples/mt_abbot_ca.html

A mass of slow-moving ice formed from accumulated snowfalls.
www.doc.ic.ac.uk/~kpt/terraquest/va/guidebook/glossary/glossary.html

A large mass of ice formed, at least in part, on land by the compaction and recrystallization of snow, moving slowly down slope or outward in all directions due to the stress of its own weight and surviving from year to year. The term "glacier" is usually, though not exclusively, confined to ice bodies that are constrained by valleys. Ice bodies that are continental in scale are usually called "ice sheets".
www.abheritage.ca/abnature/glossary.htm

Bodies of ice and compacted snow. Glaciers are formed with the termperature is too cold to allow accumulating snow to melt. The snow compacts and eventually the snow crystals change into granular ice crystals called firn. As the firn becomes buried under more accumulating snow, it changes into solid ice. The changes takes years to accomplish. There are two categories of glaciers: Alpine (which form on mountainsides) or ice sheets (which form on flat land). ...
www.educationoasis.com/curriculum/Social_Studies/geo/geography_terms.htm

a huge mass of ice and snow which moves extremely slowly (inches per year); able to scrape off and move large amounts of earth.
www.wheatonparkdistrict.com/recreation/fourth/glossary.html

A mass of ice with definite lateral limits, with motion in a definite direction, and originating from the compacting of snow by pressure.
www.lpi.usra.edu/publications/slidesets/stones/glossary.shtml

A large mass of ice which persists throughout the year, and moves slowly downslope in a liquid manor by it's own weight. Glaciers are formed in areas where the winter snow doesn't have a chance to melt, and consecutive snowfalls accumulate and compress into ice.
www.world-waterfalls.com/glossary.php

hail:
acclaim: praise vociferously; "The critics hailed the young pianist as a new Rubinstein"
be a native of; "She hails from Kalamazoo"
call for; "hail a cab"
greet enthusiastically or joyfully
precipitation of ice pellets when there are strong rising air currents
enthusiastic greeting
precipitate as small ice particles; "It hailed for an hour"
wordnet.princeton.edu/perl/webwn

Hail is a type of graupel (a form of precipitation) composed of balls or irregular lumps of ice. It occurs when supercooled water droplets (remaining in a liquid state despite being below the freezing point, 0 °C/32 °F) in a storm cloud aggregates around some solid object, such as a dust particle or an already-forming hailstone. The water then freezes around the object. ...
en.wikipedia.org/wiki/Hail

showery precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter, falling from a cumulonimbus cloud.
www.geog.ubc.ca/courses/g102/Resources/G102Glossary.html

precipitation composed of chunks of ice that form atop cumulonimbus clouds and fall as soon as they become too heavy for the cloud updrafts to hold.
www.flowmeterdirectory.com/meteorology_terms.html

Precipitation in the form of transparent or partially opaque balls or irregular lumps of concentric ice. Hail is normally defined as having a diameter of 5 millimeters or more and is produced by thunderstorms.
www.weca.org/nws-terms.html

A call to another vessel. Harbor - A safe, protected anchorage for docking and loading. Hatch - An opening in the deck, providing access to the space below. Head - This word is used in many ways in boating, the most important to those on board being "toilet." Heading - The compass direction in which a vessel is pointed at any given moment. Head sea - Waves coming from the direction in which a vessel is heading. Helm - Where the steering wheel is located. ...
www.searay.com/boating_glossary.asp

Precipitation in the form of hard pellets of ice which fall from cumulo-nimbus clouds and are often associated with thunderstorms.
www.aeroplanemonthly.com/glossary/glossary_H.htm

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.
www.telemet.com/weather_gloss_h.htm

Pieces of hard, solid ice falling from clouds.
www.bbc.co.uk/weather/weatherwise/glossary/h.shtml

Precipitation in the form of balls or irregular lumps of ice, always produced by convective clouds, nearly always cumulonimbus. An individual unit of hail is called a hailstone. By convention, hail has a diameter of 5 mm or more, while smaller particles of similar origin, formerly called small hail, may be classed as either ice pellets or snow pellets. ...
amsglossary.allenpress.com/glossary/browse

Precipitation in the form of balls or clumps of ice, produced by thunderstorms. Severe storms with intense updrafts are the most likely large hail producers.
www.srh.noaa.gov/ffc/html/spotglos.shtml

Precipitation in the forms of lumps of ice that occur with some thunderstorms.
www.cookcountysheriff.com/ema/glossary.html

a frozen form of precipitation in which droplets reach the ground still frozen as ice. Individual droplets, or hailstones, can range in size from a grain of sand to a large cobble.
www.naturalhazards.org/glossary/

A type of frozen precipitation formed when rain droplets are lofted high into the atmosphere by strong updrafts repeatedly, adding new layers of ice with each up-and-down trip, until it is finally heavy enough to fall to the ground. Hail accompanies strong thunderstorms and is usually a summertime phenomenon.
wilstar.com/skywatch_glossary.htm

Balls of ice ranging in size from tiny peas to larger than orange size
australiasevereweather.com/photography/define2.htm

millimetric or larger precipitation particle of ice, formed by the accretion of ice crystals and rapidly freezing supercooled water droplets.
www.advancedforecasting.com/weathereducation/weatherglossary.html

to call to another ship.
www.lib.mq.edu.au/all/journeys/ships/glossary.html

Pieces of ice that sometimes form in high clouds
www.rcn27.dial.pipex.com/cloudsrus/glossary.html

Precipitation in the form of nearly spherical or jagged chunks of ice; often characterized by internal concentric layering. Hail is associated with thunderstorm cells that have strong updrafts and relatively great moisture content.
www.ametsoc.org/amsedu/WES/glossary.html

precipitation in the form of hard pellets of ice or hard snow.
www.wef.org/publicinfo/NewsRoom/wastewater_glossaryK-2.jhtml

Precipitation in the form of circular or irregular-shaped lumps of ice.
weather.ncbuy.com/glossary.html

ice balls that are formed by rain that is thrown by air currents back up into a thundercloud, were a layer of ice forms around it. Hail can make several trips back up into a cloud, were it is covered with another level of ice each time.
library.thinkquest.org/3805/glossary/gloss.htm

opaque balls of ice, almost always spherical. Hail occurs in all provinces, but most frequently in Saskatchewan and Alberta, where some areas can get as many as 10 storms a year.
members.tripod.com/~MitchellBrown/almanac/weather_glossary.html

Rain that has been frozen many times on its way to the ground, creating a lumpy ball of ice.
weathereye.kgan.com/cadet/disaster/glossary.html

To attempt to contact another boat or shore, either by voice or radio.
www.terrax.org/sailing/glossary/gh.aspx

is precipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 mm (1/2 to 2 inches) or sometimes more, falling either separately or fused into irregular lumps. Hailstones are composed, almost exclusively of transparent ice, or a series of transparent ice at least 1 mm (1/25 in.) in thickness, alternating with translucent layers. Hail is generally observed during heavy thunderstorms.
www.mid-c.com/manmar/Definiti.htm

Balls of ice that grow in thunderstorm updrafts.
www.carlwozniak.com/clouds/glossary.html

此文简单介绍了什么是冰川及冰川分布
Glaciers are made up of fallen snow that, over many years, compresses into large, thickened ice masses. Glaciers form when snow remains in one location long enough to transform into ice. What makes glaciers unique is their ability to move. Due to sheer mass, glaciers flow like very slow rivers. Some glaciers are as small as football fields, while others grow to be over a hundred kilometers long.

Presently, glaciers occupy about 10 percent of the world's total land area, with most located in polar regions like Antarctica and Greenland. Glaciers can be thought as remnants from the last Ice Age, when ice covered nearly 32 percent of the land, and 30 percent of the oceans. An Ice Age occurs when cool temperature endure for extended periods of time, allowing polar ice to advance into lower latitudes. For example, during the last Ice Age, giant glacial ice sheets extended from the poles to cover most of Canada, all of New England, much of the upper Midwest, large areas of Alaska, most of Greenland, Iceland, Svalbard and other arctic islands, Scandinavia, much of Great Britain and Ireland, and the northwestern part of the former Soviet Union.

Within the past 750,000 years, scientists know that there have been eight Ice Age cycles, separated by warmer periods called interglacial periods. Currently, the Earth is nearing the end of an interglacial, meaning that another Ice Age is due in a few thousand years. This is part of the normal climate variation cycle. Greenhouse warming may delay the onset of another glacial era, but scientists still have many questions to answer about climate change. Although glaciers change very slowly over long periods, they may provide important global climate change signals.

The Big Chill
by Kirk A. Maasch

During the past billion years, the Earth's climate has fluctuated between warm periods - sometimes even completely ice-free - and cold periods, when glaciers scoured the continents. The cold periods - or ice ages - are times when the entire Earth experiences notably colder climatic conditions. During an ice age, the polar regions are cold, there are large differences in temperature from the equator to the pole, and large, continental-size glaciers can cover enormous regions of the earth.

Ever since the Pre-Cambrian (600 million years ago), ice ages have occurred at widely spaced intervals of geologic time - approximately 200 million years - lasting for millions, or even tens of millions of years. For the Cenozoic period, which began about 70 million years ago and continues today, evidence derived from marine sediments provide a detailed, and fairly continuous, record for climate change. This record indicates decreasing deep-water temperature, along with the build-up of continental ice sheets. Much of this deep-water cooling occurred in three major steps about 36, 15 and 3 million years ago - the most recent of which continues today. During the present ice age, glaciers have advanced and retreated over 20 times, often blanketing North America with ice. Our climate today is actually a warm interval between these many periods of glaciation. The most recent period of glaciation, which many people think of as the "Ice Age", was at its height approximately 20,000 years ago.

Although the exact causes for ice ages, and the glacial cycles within them, have not been proven, they are most likely the result of a complicated dynamic interaction between such things as solar output, distance of the Earth from the sun, position and height of the continents, ocean circulation, and the composition of the atmosphere.

Climatic Cooling from 60 million years ago to present day
Between 52 and 57 million years ago, the Earth was relatively warm. Tropical conditions actually extended all the way into the mid-latitudes (around northern Spain or the central United States for example), polar regions experienced temperate climates, and the difference in temperature between the equator and pole was much smaller than it is today. Indeed it was so warm that trees grew in both the Arctic and Antarctic, and alligators lived in Ellesmere Island at 78 degrees North.

But this warm period, called the Eocene, was followed by a long cooling trend. Between 52 and 36 million years ago, ice caps developed in East Antarctica, reaching down to sea level in some places. Close to Antarctica, the temperature of the water near the surface dropped to between 5 and 8 degrees Celsius. Between 36 and 20 million years ago the earth experienced the first of three major cooling steps. At this time a continental-scale temperate ice sheet emerged in East Antarctica. Meanwhile, in North America, the mean annual air temperature dropped by approximately 12 degrees Celsius.

Between 20 and 16 million years ago, there was a brief respite from the big chill, but this was followed by a second major cooling period so intense that by 7 million years ago southeastern Greenland was completely covered with glaciers, and by 5-6 million years ago, the glaciers were creeping into Scandinavia and the northern Pacific region. The Earth was once more released from the grip of the big chill between 5 and 3 million years ago, when the sea was much warmer around North America and the Antarctic than it is today. Warm-weather plants grew in Northern Europe where today they cannot survive, and trees grew in Iceland, Greenland, and Canada as far north as 82 degrees North.

We are still in the midst of the third major cooling period that began around 3 million years ago, and its effect can be seen around the world, perhaps even in the development of our own species. Around 2 and a half million years ago, tundra-like conditions took over north-central Europe. Soon thereafter, the once-humid environment of Central China was replaced by harsh continental steppe. And in sub-Saharan Africa, arid and open grasslands expanded, replacing more wooded, wetter environments. Many paleontologists believe that this environmental change is linked to the evolution of humankind.

Possible Explanations for the Past 60 Million Years of Cooling
Climate change on ultra-long time scales (tens of millions of years) are more than likely connected to plate tectonics. Plate motions lead to cycles of ocean basin growth and destruction, known as Wilson cycles, involving continental rifting, seafloor-spreading, subduction, and collision. Several explanations of the latest cooling trend that involve a climate-tectonic connection are summarized below.

Geographic Distribution and Size of Continents
Through the course of a Wilson cycle continents collide and split apart, mountains are uplifted and eroded, and ocean basins open and close. The re-distribution and changing size and elevation of continental land masses may have caused climate change on long time scales. Computer climate models have shown that the climate is very sensitive to changing geography. It is unlikely, however, that these large variations in the Earth's geography were the primary cause of the latest long-term cooling trend as they fail to decrease temperatures on a global scale.

Likewise, changing topography cannot, by itself, explain this cooling trend. Computer model experiments performed to test the climate's sensitivity to mountains and high plateaus show that plateau uplift in Tibet and western North America has a small effect on global temperature but cannot explain the magnitude of the cooling trend. Plateau uplift does, however, have a significant impact on climate, including the diversion of North Hemisphere westerly winds and intensification of monsoonal circulation.

Geometry of Ocean Basins
Another theory explaining these changes in climate involves the opening and closing of gateways for the flow of ocean currents. This theory suggests that the redistribution of heat on the planet by changing ocean circulation can isolate polar regions, cause the growth of ice sheets and sea ice, and increase temperature differences between the equator and the poles.

Ocean modeling experiments suggest that the ocean could not have carried enough heat to the poles to maintain the early warm climates. But atmospheric climate modeling experiments show that even if the ocean did transport enough heat up to the coast of Antarctica to maintain sea surface temperatures at 10 to 15 degrees Celsius, the interior conditions would still be much colder - and this is contrary to the geologic record. It is possible, however, that changes in heat transport caused by variations in ocean gateways may have played a significant role in cooling trends over the last 60 million years, and, in particular, may help explain some of the relatively sudden cooling events.

Atmospheric Carbon Dioxide
Changes in the concentration of carbon dioxide in the atmosphere are a strong candidate to explain the overall pattern of climatic change. Carbon dioxide influences the mean global temperature through the greenhouse effect. The globally averaged surface temperature for the Earth is approximately 15 degrees Celsius, and this is due largely to the greenhouse effect. Solar radiation entering earth's atmosphere is predominantly short wave, while heat radiated from the Earth's surface is long wave. Water vapor, carbon dioxide, methane, and other trace gases in the Earth's atmosphere absorb this long wave radiation. Because the Earth does not allow this long wave radiation to leave, the solar energy is trapped and the net effect is to warm the Earth. If not for the presence of an atmosphere, the surface temperature on earth would be well below the freezing point of water.

Through a million year period, the average amount of carbon dioxide in the atmosphere is affected by four fluxes: flux of carbon due to (1) metamorphic degassing, (2) weathering of organic carbon, (3) weathering of silicates, (4) burial of organic carbon. Degassing reactions associated with volcanic activity and the combining of organic carbon with oxygen release carbon dioxide into the atmosphere. Conversely, the burial of organic matter removes carbon dioxide from the atmosphere.

Plate collisions disrupt these carbon fluxes in a variety of ways, some tending to elevate and some tending to lower the atmospheric carbon dioxide level. It has been suggested that the Eocene, the early warm trend 55 million years ago, was caused by elevated atmospheric carbon dioxide and that a subsequent decrease in atmospheric carbon dioxide led to the cooling trend over the past 52 million years. One mechanism proposed as a cause of this decrease in carbon dioxide is that mountain uplift lead to enhanced weathering of silicate rocks, and thus removal of carbon dioxide from the atmosphere.

In addition, the collision of India and Asia led to the uplift of the Tibetan Plateau and the Himalayas. While topography may not be enough to explain the cooling trends, another mechanism may account for changing climate. The uplift may have caused both an increase in the global rate of chemical erosion, as well as erode fresh minerals that are rapidly transported to lower elevations, which are warmer and moister and allow chemical weathering to happen more efficiently. Through these mechanisms, then, it has been hypothesized that the tectonically driven uplift of the Tibetan Plateau and the Himalayas is the prime cause of the post-Eocene cooling trend.

Kirk A. Maasch is a professor at the University of Maine, in the Department of Geological Sciences.

ice age

Variations in CO2, temperature and dust from the Vostok ice core over the last 400,000 yearsAn ice age is a period of long-term downturn in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers ("glaciation"). Glaciologically, ice age is often used to mean a period of ice sheets in the northern and southern hemispheres; by this definition we are still in an ice age (because the Greenland and Antarctic ice sheets still exist). More colloquially, when speaking of the last few million years, ice age is used to refer to colder periods with extensive ice sheets over the North American and Eurasian continents: in this sense, the last ice age ended about 10,000 years ago. This article will use the term ice age in the former, glaciological, sense; and use the term 'glacial periods' for colder periods during ice ages and 'interglacial' for the warmer periods.

Many glacial periods have occurred during the last few million years, initially at 40,000-year frequency but more recently at 100,000-year frequencies. These are the best studied. There have been four major ice ages in the further past.

Origin of ice age theory
The idea that, in the past, glaciers had been far more extensive was folk knowledge in some alpine regions of Europe (Imbrie and Imbrie, p25, quote a woodcutter telling Jean de Charpentier of the former extent of the Swiss Grimsel glacier). No single person invented the idea [1]. Between 1825 and 1833, Charpentier assembled evidence in support of this idea. In 1836 Charpentier convinced Louis Agassiz of the theory, and Agassiz published it in his book Étude sur les glaciers of 1840.

At this early stage of knowledge, what were being studied were the glacial periods within the past few hundred thousand years, during the current ice age. The far earlier ice ages' very existence was unsuspected.

Major ice ages
There have been at least four major ice ages in the Earth's past.

The earliest hypothesized ice age is believed to have occurred around 2.7 to 2.3 billion (109) years ago during the early Proterozoic Age.

Main article: Snowball Earth
The earliest well-documented ice age, and probably the most severe of the last 1 billion years, occurred from 800 to 600 million years ago (the Cryogenian period) and it has been suggested that it produced a Snowball Earth in which permanent sea ice extended to or very near the equator. It has been suggested that the end of this ice age was responsible for the subsequent Cambrian Explosion, though this theory is recent and controversial.

A minor ice age occurred from 460 to 430 million years ago, during the Late Ordovician Period.

There were extensive polar ice caps at intervals from 350 to 260 million years ago, during the Carboniferous and early Permian Periods, associated with the Karoo Ice Age.

Sediment records showing the fluctuating sequences of glacials and interglacials during the last several million years.The present ice age began 40 million years ago with the growth of an ice sheet in Antarctica, but intensified during the Pleistocene (starting around 3 million years ago) with the spread of ice sheets in the Northern Hemisphere. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000 and 100,000 year time scales. The last glacial period ended about 10,000 years ago.

The timing of ice ages throughout geologic history is in part controlled by the position of the continental plates on the surface of the Earth. When landmasses are concentrated near the polar regions, there is an increased chance for snow and ice to accumulate. Small changes in solar energy can tip the balance between summers in which the winter snow mass completely melts and summers in which the winter snow persists until the following winter. Due to the positions of Greenland, Antarctica, and the northern portions of Europe, Asia, and North America in polar regions, the Earth today is considered prone to ice age glaciations.

Evidence for ice ages comes in various forms, including rock scouring and scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites and glacial erratics. Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret. It took some time for the current theory to be worked out. Analyses of ice cores and ocean sediment cores unambiguously show the record of glacials and interglacials over the past few million years.

Interglacials

Shows the pattern of temperature and ice volume changes associated with recent glacials and interglacialsIn between ice ages, there are multi-million year periods of more temperate, almost tropical, climate, but also within the ice ages (or at least within the last one), temperate and severe periods occur. The colder periods are called 'glacial periods', the warmer periods 'interglacials', such as the Eemian interglacial era.

We are in an interglacial period now, the last retreat ending about 10,000 years ago. There appears to be a folk wisdom that "the typical interglacial period lasts ~12,000 years" but this is hard to substantiate from the evidence of ice core records. For example, an article in Nature [2] argues that the current interglacial might be most analogous to a previous interglacial that lasted 28,000 years. Nonetheless, fear of a new glacial period starting soon does exist (See: global cooling). However, many now believe that anthropogenic (manmade) forcing from increased "greenhouse gases" would outweigh any Milankovitch (orbital) forcing; and some recent considerations of the orbital forcing have even argued that in the absence of human perturbations the present interglacial could potentially last 50,000 years.

Causes of ice ages
The cause of ice ages remains controversial for both the large-scale ice age periods and the smaller ebb and flow of glacial/interglacial periods within an ice age. The general consensus is that it is a combination of up to three different factors: atmospheric composition (particularly the fraction of CO2 and methane), changes in the Earth's orbit around the Sun known as Milankovitch cycles (and possibly the Sun's orbit around the galaxy), and the arrangement of the continents.

The first of these three factors is probably responsible for much of the change, especially for the first ice age. The "Snowball Earth" hypothesis maintains that the severe freezing in the late Proterozoic was both caused and ended by changes in CO2 levels in the atmosphere. However, the other two factors do matter.

An abundance of land within the Arctic and Antarctic Circles appears to be a necessity for an ice age, probably because the landmasses provide space on which snow and ice can accumulate during cooler times and thus trigger positive feedback processes like albedo changes. The Earth's orbit does not have a great effect on the long-term causation of ice ages, but does seem to dictate the pattern of multiple freezings and thawings that take place within the current ice age. The complex pattern of changes in Earth's orbit and the change of albedo may influence the occurrence of glacial and interglacial phases — this was first explained by the theory of Milutin Milankovic.

A glacier carried away the missing half of Half Dome in Yosemite Valley.The present ice ages are the most studied and best understood, particularly the last 400,000 years, since this is the period covered by ice cores that record atmospheric composition and proxies for temperature and ice volume. Within this period, the match of glacial/interglacial frequencies to the Milankovic orbital forcing periods is so good that orbital forcing is the generally accepted explanation. The combined effects of the changing distance to the sun, the precession of the Earth's axis, and the changing tilt of the Earth's axis can change and significantly redistribute the sunlight received by the Earth. Of particular importance are changes in the tilt of the Earth's axis, which impact the intensity of seasons. For example, the amount of solar influx in July at 65 degrees north latitude is calculated to vary by as much as 25% (from 400 W/m2 to 500 W/m2, see graph at [3]). It is widely believed that ice sheets advance when summers become too mild to melt all of the accumulated snowfall from the previous winter. Some workers believe that the strength of the orbital forcing appears to be too small to trigger glaciations, but feedback mechanisms like CO2 may explain this mismatch.

While Milankovic forcing predicts that cyclic changes in the Earth's orbital parameters can be expressed in the glaciation record, additional explanations are necessary to explain which cycles are observed to be most important in the timing of glacial/interglacial periods. In particular, during the last 800 thousand years, the dominant inter/glacial oscillation has been 100 thousand years, which corresponds to changes in Earth's eccentricity and orbital inclination, and yet is by far the weakest of the three frequencies predicted by Milankovic. During the period 3.0 — 0.8 million years ago, the dominant pattern of glaciation corresponded to the 41 thousand year period of changes in Earth's obliquity (tilt of the axis). The reasons for preferring one frequency to another are poorly understood and an active area of current research, but the answer probably relates to some form of resonance in the Earth's climate system.

The "traditional" Milankovitch explanation struggles to explain the dominance of the 100,000-year cycle over the last 8 cycles. Richard A. Muller and Gordon J. MacDonald [4] [5] [6] and others have pointed out that those calculations are for a two-dimensional orbit of Earth but the three-dimensional orbit also has a 100 thousand year cycle of orbital inclination. They proposed that these variations in orbital inclination lead to variations in insolation, as the earth moves in and out of known dust bands in the solar system. Although this is a different mechanism to the traditional view, the "predicted" periods over the last 400,000 years are nearly the same. The Muller and MacDonald theory, in turn, has been challenged by Rial [7].

Another worker, Ruddiman has suggested a plausible model that explains the 100,000 cycle by the modulating effect of eccentricity (weak 100,000 year cycle) on precession (23,000 year cycle) combined with greenhouse gas feedbacks in the 41,000 and 23,000-year cycles. Yet another theory has been advanced by Peter Huybers who argued that the 41,000-year cycle has always been dominant, but that the Earth has entered a mode of climate behavior where only the 2nd or 3rd cycle triggers an ice age. This would imply that the 100,000-year periodicity is really an illusion created by averaging together cycles lasting 80 and 120 thousand years. This theory is consistent with the existing uncertainties in dating, but not widely accepted at present (Nature 434, 2005, [8]).

Recent glacial and interglacial phases

The maximum extent of glacial ice in the north polar area during Pleistocene timeSee Timeline of glaciation.

Glaciation in North America
During the most recent North American glaciation, the Wisconsin glaciation (70,000 to 10,000 years ago), ice sheets extended to about 45 degrees north latitude.

This Wisconsinian glaciation left widespread impacts on the North American landscape. The Great Lakes and the Finger Lakes were carved by ice deepening old valleys. Most of the lakes in Minnesota and Wisconsin were gouged out by glaciers and later filled with glacial meltwaters. The old Teays River drainage system was radically altered and largely reshaped into the Ohio River drainage system. Other rivers were dammed and diverted to new channels, such as the Niagara, which formed a dramatic waterfall and gorge, when the waterflow encountered a limestone escarpment. Another similar waterfall near Syracuse, New York is now dry.

Long Island was formed from glacial till, and the watersheds of Canada were so severely disrupted that they are still sorting themselves out — the plethora of lakes on the Canadian Shield in northern Canada can be almost entirely attributed to the action of the ice. As the ice retreated and the rock dust dried, winds carried the material hundreds of miles, forming beds of loess many dozens of feet thick in the Missouri Valley. Isostatic rebound continues to reshape the Great Lakes and other areas formerly under the weight of the ice sheets.

The Driftless Zone, around the junction of Wisconsin, Minnesota, and Iowa, was not covered by glaciers.

---

岗巴县15010979902： 冰川时代三主要内容英语简介 - ？
于委碘佛： ＂Ice Age＂ of the protagonists is back! The concentration of mammoth Manny and his wife Eliza are looking forward to the birth of baby elephant; saber-toothed tiger Diageo has been suspected that they are not becoming too soft, and has not ...

岗巴县15010979902： 冰河世纪简介,英文？
于委碘佛： 20,000 years before, our planet is entering an ice age. All kinds of animals begin immigrating to the south, seeking more warm climates. Sid, a sloth who never stops talking is left behind sleeping while everyone else begins the journey to the south. ...

岗巴县15010979902： 冰川时代用英语怎么说 - ？
于委碘佛： 冰川时代 [词典] glacial age; glacial period; ice age [例句] Are they also remains of the glacial age.这应该也是冰川时代的遗迹吧?

岗巴县15010979902： 冰河世纪简介,英文 - ？
于委碘佛： Back when the Earth was being overrun by glaciers, and animals were scurrying to save themselves from the upcoming Ice Age, a stupid sloth named Sid, a woolly mammoth named Manny, a saber-toothed tiger named Diego, and an acorn-loving ...

岗巴县15010979902： 帮忙找些关于北极冰川融化的英文资料 - ？
于委碘佛： Scientists warn that there may be no ice at North Pole this summer It seems unthinkable, but for the first time in human history, ice is on course to disappear entirely from the North Pole this year.The disappearance of the Arctic sea ice, making it ...

岗巴县15010979902： 求冰河世纪(冰河时代)的资料 - ？
于委碘佛： 冰河世纪在地质历史上曾经出现过气候寒冷的大规模冰川活动的时期,称为冰期(iceage).这种冰期曾经有过三次,即前寒武晚期、石炭-二叠纪和第四纪.第四纪冰期来临的时候,地球的年平均气温曾经比现在低10℃~15℃,全球有1/3以...

岗巴县15010979902： 用英语介绍冰川时代4？
于委碘佛： “Ice age 4 ＂ story, from rat barquette and pineal Crazy Chase started, and, in the process, the earth because of Oquet's madness, by the small chain after stimulation, originally connected surface was split into seven continents four ocean, leading...

岗巴县15010979902： 冰川时代4 经典台词 英文 - ？
于委碘佛： 但愿如此不然的话被活吞的就是你You'd better, unless you want toserve as a replacement. 我们去“半峰”山去那儿会合We'll go up to Half Peak. Meet us there. 最好把他活着带来It had better be alive. 能完成这任务吗?迭戈?Can we trust you with ...

岗巴县15010979902： 我要冰川期的资料!!!! - ？
于委碘佛： 也叫冰河时代 .冰川学说专家认为,全球气候在漫长的地质年代中曾有数次冷暖变化,冰川作用随之重复发生.气候寒冷时,降雪量增加,发育大规模的冰川,巨大的冰盖掩盖地球,称为冰期;当气候变暖时,冰川大规模消退,叫做间冰期. ...

岗巴县15010979902： 冰河世纪的确切年代..还有冰河世纪2中的经典对话(英文)？
于委碘佛： 在地质历史上曾经出现过气候寒冷的大规模冰川活动的时期,称为冰期(iceage).这种冰期曾经有过三次,即前寒武晚期、石炭-二叠纪和第四纪.经典对话在网上SO不到额.建议可以直接去射手网下字幕...