Arid Regions Outline

August 30, 2003

1. Precipitation <50 cm/yr

2. Mechanical Weathering the dominant erosion process

3. Flash Floods and Wind dominant erosional agents

4. Erosional Landforms

a. Braided streams- sediment choked streams that spill out into a valley forming numerous, interwoven, shallow channels.

b. Intermittent streams- streams that carry water only part of the year.

c. Plateaus- flat upland areas away from stream valleys

d. Mesa- flat topped area wider than it is tall

e. Butte- flat topped areas as wide as it is tall

f. Monument- flat topped area taller than it is wide

g. Piedmont- gentle valleyward slope from the mountain front

i. Pediment- gently sloping erosional surface

ii. Bajada- gently sloping apron of sediment

iii. Inselberg- an erosional remenant on the pediment.

1. Depositional Landforms

a. Saltation—sand, Wind-- Loess

b. Alluvial Fan- "land deltas" deposited by streams as they become unconfined.

c. Playas- temporary lakes formed due to heavy rains in valleys with no outlet.

d. Dunes

i. Transverse- ridges of sand that form perpendicular to wind direction.

ii. Longitudinal- ridges of sand that form parallel to wind direction.

iii. Parabolic- Horns of dune point upwind, vegetation present

iv. Barchan- Horns of dune point downwind, vegetation absent