|
Ice Rafted Debris
Ice rafting is the transport of various materials by ice. Various objects deposited on ice may eventually become embedded in the ice. When the ice melts after a certain amount of drifting, these objects are deposited onto the bottom of the water body, e.g., onto a river bed or an ocean floor. These deposits are called ice rafted debris (IRD) or ice rafted deposits. Ice rafting was a primary mechanism of sediment transport during glacial episodes of the Pleistocene when sea levels were very low and much of the land was covered by large masses (sheets) of ice. The rafting of various size sediments into deeper ocean waters by icebergs became a rather important process. Ice rafting is still a process occurring today, although its impact is significantly less and much harder to gauge. The melting of large icebergs deposits sediment of various sizes, usually referred to as glacial marine sediment, onto the shelf and deeper marine areas. Ice rafting may be used for analysis of ice drif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification. Sediments are most often transported by water (fluvial processes), but also wind (aeolian processes) and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments. Classification Sediment can be classified based on its grain size, grain shape, and c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glacial Erratic
A glacial erratic is glacially deposited rock differing from the type of rock native to the area in which it rests. Erratics, which take their name from the Latin word ' ("to wander"), are carried by glacial ice, often over distances of hundreds of kilometres. Erratics can range in size from pebbles to large boulders such as Big Rock () in Alberta. Geologists identify erratics by studying the rocks surrounding the position of the erratic and the composition of the erratic itself. Erratics are significant because: *They can be transported by glaciers, and they are thereby one of a series of indicators which mark the path of prehistoric glacier movement. Their lithographic origin can be traced to the parent bedrock, allowing for confirmation of the ice flow route. *They can be transported by ice rafting. This allows quantification of the extent of glacial flooding resulting from ice dam failure which release the waters stored in proglacial lakes such as Lake Missoula. Erratics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swallow Float
John Crossley Swallow FRS (11 October 1923 – 3 December 1994) was an English oceanographer, pages 33 etter Oand 568 etter S who invented the Swallow float (sometimes referred to as a neutral buoyancy float), a scientific drifting bottle based on the messages in bottles that shipwrecked sailors hoped would reach inhabited shores, summoning assistance. He was elected a Fellow of the Royal Society in 1968. He candidature citation read: "''Dr. J.C. Swallow is internationally known both for his distinguished geophysical work on the voyages of H.M.S. "Challenger", and for his measurements of deep ocean currents. He is the inventor of the "Swallow float", a hydrostatically stable, freely drifting source of sound underwater, which can be followed by a ship at the surface. By numerous observations with this ingenious device, he and others have completely changed our picture of the deep circulation of the ocean, showing the presence of strong deep currents in the western North Atlant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dropstone
Dropstones are isolated fragments of rock found within finer-grained water-deposited sedimentary rocks or pyroclastic beds. They range in size from small pebbles to boulders. The critical distinguishing feature is that there is evidence that they were not transported by normal water currents, but rather dropped in vertically through the air or water column. Such deposition can occur i.e. during a volcanic eruption. Background When deposited into fine layered mud, such evidence includes an impact depression beneath the dropstone, and indication that the mud has been squeezed up around the edges of the falling rock. Subsequent deposits of mud drape over the dropstone and its crater. Glacial dropstones, involving rocks falling out of icebergs, are one of the most common types of dropstone preserved in the geological record, particularly when deposited in low-energy deep sea or lake environments. Dropstones differ from erratics found in glacial till in that they are deposited in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drift Station
A drifting ice station is a temporary or semi-permanent facility built on an ice floe. During the Cold War the Soviet Union and the United States maintained a number of stations in the Arctic Ocean on floes such as Fletcher's Ice Island for research and espionage, the latter of which were often little more than quickly constructed shacks. Extracting personnel from these stations proved difficult and in the case of the United States, employed early versions of the Fulton surface-to-air recovery system. Overview Soviet and Russian staffed drifting ice stations are research stations built on the ice of the high latitudes of the Arctic Ocean. They are important contributors to exploration of the Arctic. The stations are named North Pole (NP; russian: Северный полюс, translit=Severny polyus, ), followed by an ordinal number: North Pole-1, etc. NP drift stations carry out the program of complex year-round research in the fields of oceanology, ice studies, meteorology, aer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
