EV29 - Arid Landforms

1) Mesa-and-Scarp Terrain 2) Mesa 3) scarp

(1) - (2) means table and (3) means steep, more or less vertical cliffs. This terrain is normally associated with horizontal sedimentary strata - shown off prominently in this arid region because it lacks a continuous cover of trees and vegetation. Such strata invariably offer different degrees of resistance to weathering and erosion, and so abrupt changes in slope angle are characteristic of this terrain.

1) Playas

(1) - Dry lake beds found in basins of interior drainage. Formed when water fills a basin and evaporates.

1) Fluvial Deposition 2) Ephemeral

*Special Conditions in Deserts that Influence Land Development* (1) - (2) streams (streams that only run with water after a big rain) are effective agents of erosion, shifting enormous amounts of material in a short time. Once the stream dries up, the load is dropped and waits for the next big rain. Thus, depositional features of alluvium are unusually common in desert areas.

1) Soil Creep

*Special Conditions in Deserts that Influence Land Development* (1) - Almost nonexistent because of the lack of soil and the lack of the lubricating effect of water. (1) is a smoothing process in more humid climates, and its lack in deserts accounts in part for the angularity of desert slopes.

1) Basins of Interior Drainage

*Special Conditions in Deserts that Influence Land Development* (1) - Desert areas contain many watersheds that do not drain to the ocean because they have no external outlet. Rain that falls in these areas has no chance of reaching the sea by a stream.

1) Sand 2) little drainage 3) heavy rain 4) wind

*Special Conditions in Deserts that Influence Land Development* (1) - Most deserts are actually not covered in this, but the ones that are experience 3 big effects on their topography. The first is the (2) via overland flow or streams because the (1) absorbs most of the water. Second, a (3) can move large amounts of sand. And third, (4) can transport and redeposit sand creating desert sand dunes.

1) Vegetation

*Special Conditions in Deserts that Influence Land Development* (1) - The lack of a continuous cover of (1) causes slopes to be steeper in dry climates because the surface material isn't bound adequately with roots.

1) Soil and Regolith

*Special Conditions in Deserts that Influence Land Development* (1) - Thin or absent in most places, which exposes the bedrock to weathering and erosion and contributes to the stark, rugged, rocky terrain.

1) runoff 2) fluvial erosion and deposition

*Special Conditions in Deserts that Influence Land Development* Rainfall) - limited in desert areas, much of it comes from intense convective thunderstorms - which result in very high and rapid (1). Floods, though brief and covering a little amount of area, causes remarkably effective (2).

1) mechanical

*Special Conditions in Deserts that Influence Land Development* Weathering) - The lack of water, plants, and animals in deserts causes (1) weathering to dominate.

1) Erg "A Sea of Sand"

*The Influence of Wind * (1) - A large area covered with loose sand generally arranged in some sort of dune formation by the wind. The classic Arabic desert.

1) Reg "Stony Deserts" 2) desert pavement

*The Influence of Wind * (1) - A tight covering of coarse gravel, pebbles, and/or boulders from which all sand and dust have been removed by wind and water. The finer material was removed through surface erosion - perhaps aided by sediment movement below the surface through the action of rainwater percolation - so the surface pebbles often fit closely together, sealing whatever material is below from further erosion. For this reason, a (1) is often referred to as (2).

1) Aeolian Transportation

*The Influence of Wind * (1) - Similar to fluvial transportation. The finest particles are carried in suspension as dust. Dust storms can hold thousands of tons of suspended dust and extend for hundreds of meters above Earth's surface and more that 1600 km (1000 mi) horizontally. Larger particles are moved by saltation (bouncing) and traction (rolling and sliding).

1) Deflation Erosion

*The Influence of Wind * (1) - The shifting of loose particles as a result of their being blown either through the air or along the ground. (1) is a factor in the formation of "reg" surface, along with fluvial erosion.

1) abration

*The Influence of Wind * (1) - aeolian (1) is analogous to fluvial abrasion, except that the Aeolian variety is much less effective. (1) is when wind drives airborne sand and dust particles against rock and soil surfaces in a form of natural sandblasting. It doesn't construct or even significantly shape a landform; it merely shapes those already in existence.

1) Aeolian Erosion 2) deflation 3) abrasion

*The Influence of Wind * (1) - processes that are related to wind action and are most pronounced in deserts. The erosive effects of wind are either (2) or (3).

1) Piedmont Zone 2) bajadas

*Water - The Dominant Land-Forming Agent in Arid Regions* (1) - A generic term meaning any zone at the foot of a mountain range. In deserts, a (1) is a prominent area of fluvial deposition. This is characterized by a pronounced change in slope. Alluvial fans and (2) (a series of alluvial fans) are found here.

1) Exotic Streams

*Water - The Dominant Land-Forming Agent in Arid Regions* (1) - A stream that is able to survive its way through the desert. It has no feeder rivers.

1) Fluvial Deposition in Arid Landscapes 2) talus 3) alluvium

*Water - The Dominant Land-Forming Agent in Arid Regions* (1) - Mostly consist of (2) accumulations at the foot of steep slopes and deposits of (3) and other fragmented debris in ephemeral stream channels.

1) Saline Lake

*Water - The Dominant Land-Forming Agent in Arid Regions* (1) - Permanent desert lakes where dissolved salts accumulate because of high rates of evaporation relative to the inflow and/or basins of interior drainage. Many of these lakes in deserts are just remnants of even larger bodies of water that were formed many moons ago when the climate was wetter.

1) Ephemeral Streams (seasonal streams)

*Water - The Dominant Land-Forming Agent in Arid Regions* (1) - Streams that are usually just dry beds with flat floor, sandy bottoms, and steep sides, but after convective thunderstorms they will flow fast and rapid, causing intense erosion, transportation, and deposition. They will occasionally reach a sea, lake, or exotic river.

1) variations 2) Rocks resistant to erosion 3) softer rocks

*Water - The Dominant Land-Forming Agent in Arid Regions* Differential Weathering and Erosion in Deserts) - A result of (1) in rock type and structure that influences the rate of weathering, and in turn, the ease of erosion. (2) form the cliffs, pinnacles, spires, and other sharp crests, while (3) wear away more rapidly to produce gentler slopes.

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Basin and Range Mesa-and-Scarp Terrain

The 2 Major U.S. Southwest Landscapes