Earth SC glacial and Arid

What types of deposits are generated by wind?

*Loess* is an extensive accumulation of windblown silt *Dunes* are asymmetrical accumulations of sand saltated by wind

Extent of Ice Age Glaciation

-Last ice age began between 2 and 3 million years ago during the Quaternary Period -Ice sheets and alpine glaciers were far more extensive than they are today -Almost 30% of Earth's land was glacially influenced

How do glaciers erode Earth's surface and what landforms do they create?

-Plucking (picking up large pieces of bedrock) -Abrasion (grinding and polishing bedrock) -Landforms include: glacial troughs, hanging valleys, cirques, arêtes, horns, and fiords

End moraines

-form at the terminus of a glacier (glacial balance in equilibrium)

Medial moraines

-form between two advancing glaciers -Dark stripe of debris within the glacier

Deserts

30% of Earth's land surface is arid Concentrated in subtropics and middle latitudes Affected by many geologic processes Mountain building, running water, wind

Ice sheets

=are found at the poles •Flow out in all directions from a center of snow accumulation •Large scale, obscure underlying terrain

glacier

A glacier is a thick (100s - 1000s of m) mass of ice​ Originates by accumulation, compaction, and recrystallization of snow​ Glaciers move slowly because of gravity​ Accumulate, transport, and deposit sedimen

Wind Erosion: Different from a River

Different from a river Less capable of transporting coarse material Not confined to a channel Relatively insignificant erosional agent

Wind Deposits

Generally two distinctive types: -Extensive blankets of silt from suspended load called *loess* -Mounds and ridges of sand from bed load called *dunes*

Deflation

Lifting and removal of loose material Clay and silt only

Middle-latitude deserts and steppes occur in the *deep interiors of large landmasses*

Little precipitation because of distance to oceans Example of how geologic processes (mountain building) can affect climate

Loess

Loess is windblown silt Tends to erode in vertical cliffs Lacks bedding Deserts and glacial deposits of stratified drift are primary sources of silt

Wind Erosion: similar to a river

Moving air can pick up and transport loose material Similar to a river Velocity of wind increases with height above surface Transports fine particles in suspension and heavier particles as bed load

Saltation

Rolling or skipping of larger particles along the surface

Blowouts

Shallow depressions caused by deflation

Dry climate

Yearly precipitation less than the potential loss of water by evaporation -*Desert* (arid) *Steppe *(semiarid)

Lateral moraines

form along the sides of the valley

Ice shelves

form when glacial ice flows into the ocean •Large, relatively flat •Attached to land and flow outward away from coast •Become thinner seaward

Valley or alpine glaciers

occur in valleys in high mountains​ Relatively small​ Advance slowly (a few cm per day)​ Flow downvalley from an accumulation center​ Generally width is narrow relative to length

Desert pavement

Stony veneer left behind after deflation removes finer material

African, Arabian, and Australian deserts are a result of* prevailing winds*

Subtropical highs in the lower latitudes Subsiding air is compressed and warmed Creates clear skies and ongoing dryness

sea ice

The Arctic Ocean is covered by *sea ice*(frozen seawater) •Floats •Ranges from a few cm to 4 m thick •Expands and contracts with the seasons

Ground moraines

are gently rolling layers of till deposited as the terminus retreats

Moraines

are layers or ridges of till. the ground sediments being pushed by the glacier forms a ridge.

Ice caps

•Cover uplands and high plateaus •Smaller than ice sheets but bury underlying terrain

Outlet glaciers

•Extend out from ice caps and ice sheets

Piedmont glaciers

•Form in broad lowlands at the base of mountains •Form when glaciers emerge from the confining walls of a valley

Glacial Erosion

•Glaciers erode and transport tremendous volumes of rock •Debris cannot settle out like sediment carried by water or wind •Capable of carrying very large pieces of debris

2) Ice sheets

•Greenland and Antarctica •Extensive ice sheets during the Last Glacial Maximum (~18,000 years ago) •Also covered North America, Europe, and Siberia •Ice sheets have advanced and retreated several times over the last 2.6 million years