Wind and Ice PDF - Chapter 8, Section 2&3

10/29/2024 Chapter 8 Section 2& 3 How do dunes form and migrate? 1  10/29/2024 Water is in what state of matter...

10/29/2024 Chapter 8 Section 2& 3 How do dunes form and migrate? 1  10/29/2024 Water is in what state of matter when we examine glaciers? Wind Erosion and Transport Limited precipitation leads to an increase in the amount of wind erosion because precipitation holds down sediments and allows plants to grow. Wind transport and erosion primarily occur in areas with little vegetative cover, such as deserts, semiarid areas, seashores, and some lakeshores. Copyright © McGraw-Hill Education Wind 2  10/29/2024 Wind Erosion and Transport Deflation The lowering of the land surface that results from the wind’s removal of surface particles is called deflation. During the 1930s, portions of the Great Plains region experienced severe drought. Because large areas of natural vegetation had been removed, strong winds readily picked up the dry surface particles. The region became known as the Dust Bowl. Copyright © McGraw-Hill Education Wind Wind Erosion and Transport Abrasion Another process of erosion, called abrasion, occurs when particles such as sand rub against the surface of rocks or other materials. Because sand is often made of quartz, a hard mineral, wind abrasion can be an effective agent of erosion—windblown sand particles eventually wear away rocks. Copyright © McGraw-Hill Education Wind 3  10/29/2024 Wind Erosion and Transport Abrasion Rocks shaped by windblown sediments are called ventifacts. Copyright © McGraw-Hill Education Wind Dune 4  10/29/2024 Wind Deposition Dunes In windblown environments, sand particles tend to accumulate where an object, such as a rock, landform, or piece of vegetation, blocks the forward movement of the particles. Over time, the pile of windblown sand develops into a dune. Copyright © McGraw-Hill Education Wind Wind Deposition Dunes The conditions under which a dune forms determine its shape and include the availability of sand, wind velocity, wind direction, and the amount of vegetation present. Dune migration is caused when prevailing winds continue to move sand from the windward side of a dune to its leeward side, causing the dune to move slowly over time. Copyright © McGraw-Hill Education Wind 5  10/29/2024 Wind Deposition Loess Thick, windblown silt deposits are known as loess. Loess soils are some of the most fertile soils because they contain abundant minerals and nutrients. Copyright © McGraw-Hill Education Wind Moving Masses of Ice A large mass of moving ice is called a glacier. Glaciers form near Earth’s poles and in mountainous areas at high elevations. They cover about 10 percent of Earth’s surface Copyright © McGraw-Hill Education Glaciers 6  10/29/2024 Moving Masses of Ice Valley glaciers Glaciers that form in valleys in high, mountainous areas are called valley glaciers. As valley glaciers flow downslope, they carve V-shaped stream valleys into U-shaped glacial valleys. Copyright © McGraw-Hill Education Glaciers Moving Masses of Ice Continental glaciers Glaciers that cover broad, continent-sized areas are called continental glaciers. These glaciers form in cold climates where snow accumulates over many years. Copyright © McGraw-Hill Education Glaciers 7  10/29/2024 Moving Masses of Ice Glacial movement Both valley glaciers and continental glaciers move outward when snow gathers at the zone of accumulation, a location in which more snow falls than melts, evaporates, or sublimates. Copyright © McGraw-Hill Education Glaciers Glacial Erosion Of all the erosional agents, glaciers are the most powerful because of their great size and weight. When a valley glacier moves, it breaks off pieces of rock through a process called plucking. When glaciers with embedded rocks move over bedrock, they act like grains on a piece of sandpaper, grinding parallel scratches into the bedrock. Copyright © McGraw-Hill Education Glaciers 8  10/29/2024 Glacial Erosion At the high elevations where snow accumulates, valley glaciers scoop out deep, bowl-shaped depressions, called cirques. When there are glaciers on three or more sides of a mountaintop, the carving action creates a steep, pyramid-shaped peak, called a horn. Hanging valleys are formed by valley glaciers when higher tributary glaciers converge with the lower primary glaciers and later retreat. A valley is left hanging high above the primary valley floor. Copyright © McGraw-Hill Education Glaciers Glacial Deposition Glacial till is the unsorted rock, gravel, sand, and clay that glaciers carry embedded in their ice and on their tops, sides, and front edges. Glaciers deposit unsorted ridges of till called moraines when the glacier retreats. Copyright © McGraw-Hill Education Glaciers 9  10/29/2024 Glacial Deposition Outwash When the farthest ends of a glacier melt, meltwater floods the valley below. Outwash is the gravel, sand, and fine silt sediment that is deposited by meltwater carried away from the glacier. The area at the leading edge of a glacier where meltwater flows and deposits outwash is called an outwash plain. Copyright © McGraw-Hill Education Glaciers Glacial Deposition Drumlins, eskers, and kames Continental glaciers that move over older moraines form the material into elongated landforms called drumlins. Streams flowing under melting glaciers leave long, winding ridges of layered sediments called eskers. A kame is a mound of layered sediment that forms when till gets washed into depressions or openings in the melting ice. Copyright © McGraw-Hill Education Glaciers 10  10/29/2024 Visualizing Continental Glacial Features Continental glaciers carve out vast regions of landscape, leaving behind distinctive features such as kames, eskers, drumlins, and moraines. Copyright © McGraw-Hill Education Glaciers Glacial Deposition Glacial lakes Kettles, or kettle lakes, form when water from runoff or precipitation fills a hole that formed when a large block of ice broke off a continental glacier and melted. With valley glaciers, cirques can also fill with water and become cirque lakes. When a terminal moraine blocks off a valley, the valley fills with water to form a moraine-dammed lake. Copyright © McGraw-Hill Education Glaciers 11