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Moulin (geomorphology)
A moulin (or glacier mill) is a roughly circular, vertical (or nearly vertical) well-like shaft formed where a surface meltstream exploits a weakness in the ice. The term is derived from the French word for mill.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. They can be up to 10 meters wide and are typically found on ice sheets and flat areas of a glacier in a region of transverse crevasses. Moulins can reach the bottom of the glacier, hundreds of meters deep, or may only reach the depth of common crevasse formation (about 10–40 m) where the stream flows englacially. They are the most typical cause for the formation of a glacier cave. Moulins are parts of the internal structure of glaciers, that carry meltwater from the surface down to wherever it may go. Water from a moulin often exits the glacier at base level, sometimes into the sea, and occa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moulin On Snowbird Glacier, Below The Snowbird Glacier Hut
Moulins or Moulin ( French for ''mill'') may refer to: Places France * Diocese of Moulins * Moulins, Allier, in the Allier department (the largest Moulins) * Moulins, Aisne, in the Aisne department * Moulins, Ille-et-Vilaine, in the Ille-et-Vilaine department * Moulins-Engilbert, in the Nièvre department * Moulins-en-Tonnerrois, in the Yonne department * Moulins-la-Marche, in the Orne department * Moulins-le-Carbonnel, in the Sarthe department * Moulins-lès-Metz, in the Moselle department * Moulins-Saint-Hubert, in the Meuse department * Moulins-sur-Céphons, in the Indre department * Moulins-sur-Orne, in the Orne department * Moulins-sur-Ouanne, in the Yonne department * Moulins-sur-Yèvre, in the Cher department * Moulin-Mage, in the Tarn department * Moulin-Neuf, Ariège, in the Ariège department * Moulin-Neuf, Dordogne, in the Dordogne department * Moulin-sous-Touvent, in the Oise department Scotland *Moulin, Scotland, a small settlement just outside Pitlochry, in Pert ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geophysical Research Letters
''Geophysical Research Letters'' is a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union that was established in 1974. The editor-in-chief is Harihar Rajaram. Aims and scope The journal aims for rapid publication of concise research reports on one or more of the disciplines covered by the American Geophysical Union, such as atmospheric sciences, solid Earth, space science, oceanography, hydrology, land surface processes, and the cryosphere. The journal also publishes invited reviews that cover advances achieved during the past two or three years. The target readership is the earth science community, the broader scientific community, and the general public. Abstracting and indexing This journal is abstracted and indexed in: According to the 2020 ''Journal Citation Reports'', the journal has a 2019 impact factor of 4.58. ''Geophysical Research Letters'' was also the 5th most cited publication on climate change between 1999 and 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supraglacial Lake
A supraglacial lake is any pond of liquid water on the top of a glacier. Although these pools are ephemeral, they may reach kilometers in diameter and be several meters deep. They may last for months or even decades at a time, but can empty in the course of hours. Lifetime Lakes may be created by surface melting during summer months, or over the period of years by rainfall, such as monsoons. They may dissipate by overflowing their banks, or creating a moulin. Effects on ice masses Lakes of a diameter greater than ~300 m are capable of driving a fluid-filled crevasse to the glacier/bed interface, through the process of hydrofracture. A surface-to-bed connection made in this way is referred to as a moulin. When these crevasses form, it can take a mere 2–18 hours to empty a lake, supplying warm water to the base of the glacier - lubricating the bed and causing the glacier to surge. The rate of emptying such a lake is equivalent to the rate of flow of the Niagara Falls. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subglacial Lake
A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where gravitational pressure decreases the pressure melting point of ice. Over time, the overlying ice gradually melts at a rate of a few millimeters per year. Meltwater flows from regions of high to low hydraulic pressure under the ice and pools, creating a body of liquid water that can be isolated from the external environment for millions of years. Since the first discoveries of subglacial lakes under the Antarctic Ice Sheet, more than 400 subglacial lakes have been discovered in Antarctica, beneath the Greenland Ice Sheet, and under Iceland's Vatnajökull ice cap. Subglacial lakes contain a substantial proportion of Earth's liquid freshwater, with the volume of Antarctic subglacial lakes alone estimated to be about 10,000 km3, or about 15% of all liquid freshwater on Earth. As ecosystems is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snake Coils (geology)
Snake coils is a descriptive term used by physical geologists and glaciologists to describe the "snake coil"-like shape that occurs along certain ablation lines. Essentially miniature tunnel valley A tunnel valley is a U-shaped valley originally cut under the glacial ice near the margin of continental ice sheets such as that now covering Antarctica and formerly covering portions of all continents during past glacial ages. They can be as l ...s, the peculiar natural shapes were first described by French geologist Jean-Jerome Peytavi in 1973 during an expedition to northern Greenland, and later confirmed by a team of Danish geologists. It is believed that snake coils are formed through the same mechanism as tunnel valleys. References *Benn, D.I. & Evans, D.J.A. ''Glaciers & Glaciation''. Hodder Arnold Pubs; (1998). *Plummer, Charles C., ''Physical Geology''. McGraw-Hill; 10 edition (2004). *Tarbuck, Edward J., ''Earth: An Introduction to Physical Geology''. Prentice Hall; 8 editi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinkhole
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openings where surface water enters into underground passages known as ''ponor'', swallow hole or swallet. A ''cenote'' is a type of sinkhole that exposes groundwater underneath. A ''sink'' or ''stream sink'' are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock. Most sinkholes are caused by karst processes – the chemical dissolution of carbonate rocks, collapse or suffosion processes. Sinkholes are usually circular and vary in size from tens to hundreds of meters both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide. Formation Natural processes Sinkholes may capture surf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Névé
Névé is a young, granular type of snow which has been partially melted, refrozen and compacted, yet precedes the form of ice. This type of snow is associated with glacier formation through the process of ''nivation''. Névé that survives a full season of ablation turns into firn, which is both older and slightly denser. Firn eventually becomes glacial ice – the long-lived, compacted ice that glaciers are composed of. Glacier formation can take days to years depending on freeze-thaw factors. Névé is annually observed in skiing slopes, and is generally disliked as an icy falling zone. Névé has a minimum density of 500 kg/m3, which is roughly half of the density of liquid water at 1 atm. Névé can also refer to the alpine Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine Nati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melt Pond
Melt ponds are pools of open water that form on sea ice in the warmer months of spring and summer. The ponds are also found on glacial ice and ice shelves. Ponds of melted water can also develop under the ice. Melt ponds are usually darker than the surrounding ice, and their distribution and size is highly variable. They absorb solar radiation rather than reflecting it as ice does and, thereby, have a significant influence on Earth's radiation balance. This differential, which had not been scientifically investigated until recently, has a large effect on the rate of ice melting and the extent of ice cover. Melt ponds can melt through to the ocean's surface. Seawater entering the pond increases the melt rate because the salty water of the ocean is warmer than the fresh water of the pond. The increase in salinity also depresses the water's freezing point. Water from melt ponds over land surface can run into crevasses or moulins – tubes leading under ice sheets or glaciers � ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocene Glacial Retreat
The Holocene glacial retreat is a geographical phenomenon that involved the global retreat of glaciers ( deglaciation) that previously had advanced during the Last Glacial Maximum. Ice sheet retreat initiated ca. 19,000 years ago and accelerated after ca. 15,000 years ago. The Holocene, starting with abrupt warming 11,700 years ago, resulted in rapid melting of the remaining ice sheets of North America and Europe. Geographical alterations Antarctica Radiocarbon dating has been used to date the start of glacial retreat on Alexander island 18,000 years ago. The outermost locations like Marguerite Bay were fully deglaciated 12,000 years ago and the further inland locations continued deglaciating for an additional 3,000 years. The Larsen ice shelf was formed in the early Holocene at a latest estimation of 10,700 years ago. Certain segments of the ice shelf have collapsed as recently as 1995 for Larsen A and a large segment of Larsen B collapsed in 2002. Europe The many valleys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant's Kettle
A giant's kettle, also known as either a giant's cauldron, moulin pothole, or glacial pothole, is a typically large and cylindrical pothole drilled in solid rock underlying a glacier either by water descending down a deep moulin or by gravel rotating in the bed of subglacial meltwater stream.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. The interiors of potholes tend to be smooth and regular, unlike a plunge pool. An example is the large pothole found in Archbald, Pennsylvania, in Archbald Pothole State Park. Formation Giant's kettles are formed while a bedrock surface is covered by a glacier. Water, produced by the thawing of the ice and snow, forms streams on the surface of the glacier, which, having gathered into their courses a certain amount of morainic debris, finally flow down a crevasse as a swirling cascade or moulin. The sides of the crevasse are a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firn
__NOTOC__ Firn (; from Swiss German "last year's", cognate with ''before'') is partially compacted névé, a type of snow that has been left over from past seasons and has been recrystallized into a substance denser than névé. It is ice that is at an intermediate stage between snow and glacial ice. Firn has the appearance of wet sugar, but has a hardness that makes it extremely resistant to shovelling. Its density generally ranges from 0.35 g/cm3 to 0.9 g/cm3, and it can often be found underneath the snow that accumulates at the head of a glacier. Snowflakes are compressed under the weight of the overlying snowpack. Individual crystals near the melting point are semiliquid and slick, allowing them to glide along other crystal planes and to fill in the spaces between them, increasing the ice's density. Where the crystals touch they bond together, squeezing the air between them to the surface or into bubbles. In the summer months, the crystal metamorphosis can occur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Calving
Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier.Essentials of Geology, 3rd edition, Stephen Marshak It is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse. The ice that breaks away can be classified as an iceberg, but may also be a growler, bergy bit, or a crevasse wall breakaway.Glossary of Glacier Terms Ellin Beltz, 2006. Retrieved July 2009. Calving of glaciers is often accompanied by a loud cracking or booming sound before blocks of ice up to high break loose and crash into the water. The entry of the ice into the water causes large, and often hazardous waves. The waves formed in locations like |
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