Drift (geology)

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Rounded erratic boulders of crystalline rock composition that have been drifted next to Ordovician limestone bank along the shoreline in NW Osmussaar, Estonia. Randkivid Osmussaar.JPG
Rounded erratic boulders of crystalline rock composition that have been drifted next to Ordovician limestone bank along the shoreline in NW Osmussaar, Estonia.

In geology, drift is the name for all material of glacial origin found anywhere on land or at sea, [1] including sediment and large rocks (glacial erratic). Glacial origin refers to erosion, transportation and deposition by glaciers.

Geology The study of the composition, structure, physical properties, and history of Earths components, and the processes by which they are shaped.

Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon. Modern geology significantly overlaps all other earth sciences, including hydrology and the atmospheric sciences, and so is treated as one major aspect of integrated earth system science and planetary science.

Glacial erratic piece of rock that differs from the size and type of rock native to the area in which it rests

A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests. "Erratics" take their name from the Latin word errare, and 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.

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In the UK, the term 'drift' is commonly used to describe any deposits of Quaternary age.[ citation needed ]

Deposition (geology) Geological process in which sediments, soil and rocks are added to a landform or land mass

Deposition is the geological process in which sediments, soil and rocks are added to a landform or land mass. Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.

Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene and the Holocene. The informal term "Late Quaternary" refers to the past 0.5–1.0 million years.

The Driftless Area refers to an unglaciated portion of North America devoid of the glacial drift of surrounding regions.

Driftless Area Area of the American Midwest which was not affected by glaciers during the last ice age

The Driftless Area is a region in southwestern Wisconsin, southeastern Minnesota, northeastern Iowa, and the extreme northwestern corner of Illinois, of the American Midwest. The region escaped glaciation during the last ice age and is consequently characterized by steep, forested ridges, deeply carved river valleys, and karst geology characterized by spring-fed waterfalls and cold-water trout streams. Ecologically, the Driftless Area's flora and fauna are more closely related to those of the Great Lakes region and New England than those of the broader Midwest and central Plains regions. Colloquially, the term includes the incised Paleozoic Plateau of southeastern Minnesota and northeastern Iowa. The region includes elevations ranging from 603 to 1,719 feet at Blue Mound State Park and covers 24,000 square miles (62,200 km2). The rugged terrain is due both to the lack of glacial deposits, or drift, and to the incision of the upper Mississippi River and its tributaries into bedrock.

North America Continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere

North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It is also considered by some to be a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.

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Glacier Persistent body of ice that is moving under its own weight

A glacier is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs, and other distinguishing features. They also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.

Moraine Glacially formed accumulation of unconsolidated debris

A moraine is any glacially formed accumulation of unconsolidated glacial debris that occurs in both currently and formerly glaciated regions on Earth, through geomorphological processes. Moraines are formed from debris previously carried along by a glacier, and normally consist of somewhat rounded particles ranging in size from large boulders to minute glacial flour. Lateral moraines are formed at the side of the ice flow and terminal moraines at the foot, marking the maximum advance of the glacier. Other types of moraine include ground moraines and medial moraines.

Till Unsorted glacial sediment

Till or glacial till is unsorted glacial sediment.

Prairie ecosystems considered part of the temperate grasslands, savannas, and shrublands biome

Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type. Temperate grassland regions include the Pampas of Argentina, Brazil and Uruguay, and the steppe of Ukraine, Russia and Kazakhstan. Lands typically referred to as "prairie" tend to be in North America. The term encompasses the area referred to as the Interior Lowlands of Canada, the United States, and Mexico, which includes all of the Great Plains as well as the wetter, hillier land to the east.

Glaciology Scientific study of ice and natural phenomena involving ice

Glaciology is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice.

A kame delta is a glacial landform formed by a stream of melt water flowing through or around a glacier and depositing material, known as kame deposits. Upon entering a proglacial lake at the end (terminus) of a glacier, the river/stream deposit these sediments. This landform can be observed after the glacier has melted and the delta's asymmetrical triangular shape is visible. Once the glacier melts, the edges of the delta may subside as ice under it melts. Glacial till is deposited on the lateral sides of the delta, as the glacier melts.

Geology of the Yosemite area

The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.

Glacial landform Landform created by the action of glaciers

Glacial landforms are landforms created by the action of glaciers. Most of today's glacial landforms were created by the movement of large ice sheets during the Quaternary glaciations. Some areas, like Fennoscandia and the southern Andes, have extensive occurrences of glacial landforms; other areas, such as the Sahara, display rare and very old fossil glacial landforms.

Glacial lake lake formed by a melted glacier

A glacial lake is a body of water with origins from glacier activity. They are formed when a glacier erodes the land, and then melts, filling the depression created by the glacier.

Otto Martin Torell Swedish scientist

Prof Otto Martin Torell HFRSE was a Swedish naturalist and geologist.

Fluvio refers to things related to rivers and glacial refers to something that is of ice. Fluvio-glacial refers to the meltwater created when a glacier melts. Fluvio-glacial processes can occur on the surface and within the glacier. The deposits that happen within the glacier are revealed after the entire glacier melts or partially retreats. Fluvio-glacial landforms and erosional surfaces include: outwash plains, kames, kame terraces, kettle holes, eskers, varves, and proglacial lakes.

Boulder clay A deposit of clay, often full of boulders, formed from the ground moraine material of glaciers and ice-sheets

Boulder clay is a geological deposit of clay, often full of boulders, which is formed out of the ground moraine material of glaciers and ice-sheets. It was the typical deposit of the Glacial Period in northern Europe and North America.

Superficial deposits refer to geological deposits typically of Quaternary age. These geologically recent unconsolidated sediments may include stream channel and floodplain deposits, beach sands, talus gravels and glacial drift and moraine. All pre-Quaternary deposits are referred to as bedrock.

U-shaped valley Valleys formed by glacial scouring

U-shaped valleys, trough valleys or glacial troughs, are formed by the process of glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape, with steep, straight sides and a flat or rounded bottom. Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring. When the ice recedes or thaws, the valley remains, often littered with small boulders that were transported within the ice, called glacial till or glacial erratic.

Geology of Minnesota

The geology of Minnesota comprises the rock, minerals, and soils of the U.S. state of Minnesota, including their formation, development, distribution, and condition.

Glacial history of Minnesota

The glacial history of Minnesota is most defined since the onset of the last glacial period, which ended some 10,000 years ago. Within the last million years, most of the Midwestern United States and much of Canada were covered at one time or another with an ice sheet. This continental glacier had a profound effect on the surface features of the area over which it moved. Vast quantities of rock and soil were scraped from the glacial centers to its margins by slowly moving ice and redeposited as drift or till. Much of this drift was dumped into old preglacial river valleys, while some of it was heaped into belts of hills at the margin of the glacier. The chief result of glaciation has been the modification of the preglacial topography by the deposition of drift over the countryside. However, continental glaciers possess great power of erosion and may actually modify the preglacial land surface by scouring and abrading rather than by the deposition of the drift.

Geology of Yorkshire

The Geology of Yorkshire in northern England shows a very close relationship between the major topographical areas and the geological period in which their rocks were formed. The rocks of the Pennine chain of hills in the west are of Carboniferous origin whilst those of the central vale are Permo-Triassic. The North York Moors in the north-east of the county are Jurassic in age while the Yorkshire Wolds to the south east are Cretaceous chalk uplands. The plain of Holderness and the Humberhead levels both owe their present form to the Quaternary ice ages. The strata become gradually younger from west to east.

Ice rafting The transport of various materials by drifting ice

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.

Kankakee Torrent

The Kankakee Torrent was a catastrophic flood that occurred about 19,000 BP calibrated years ago in the Midwestern United States. It resulted from a breach of moraines forming a large glacial lake fed by the melting of the Late Wisconsin Laurentide Ice Sheet. The point of origin of the flood was Lake Chicago. The landscape south of Chicago still shows the effects of the torrent, particularly at Kankakee River State Park and on the Illinois River at Starved Rock State Park.

References

  1. Press, Frank; Siever, Raymond (1986). "Glaciers". Earth (Fourth ed.). New York, NY: W. H. Freeman and Company. p. 248. ISBN   978-0716717430.