Engineering Geology - Chapter 13 - Deserts

• Possible Answers:
• barchan dunes;
• transverse dunes;
• parabolic dunes;
• longitudinal dunes.

• -Barchan dunes generally develops where the sand supply is limited.
• -Crescent shaped dune with a steep face on the inward or concave side. The horns of the crescent point downwind. 
• -They are typically seperate from one another and move across a baren surface.

• -Transverse dune form when more sand is available
• -Long and relatively straight dunes oriented perpendicular to the wind direction.

• Parabolic Dunes are similar in shape to barchan dunes, but require a lot more sand and very strong winds.
• They are more deeply curved and the horns point upwind instead. Vegetation commonly anchors the horns
• Commonly found inland from an ocean beach. 

• Longitudianl Dunes are the largest dunes.
• Very tall/large symmetrical ridges that are exceptionally straight and evenly spaced. 
• Scientists aren't sure how they are formed, but some theories suggest that it has something to do with crosswinds.

the Colorado Plateau; and the Basin and Range province.

Loess

Playa: A very flat surface underlain by a dry lake bed of hard, mud-cracked clay

soil consisting of silt and clay particles deposited by wind

D. size

B. Nevada

Rocks with flat, wind-abraded surfaces

C. all of the preceding are dunes

a broad flat-topped area elevated above the surrounding land and a steep cliff face.

Both are remnants left over when a plateau erodes away. They are like flat-topped hills with steep, cliff sides and capped by a resistant rock layer. A mesa is large and broad, while a butte is narrow and small. Most buttes form from the continued erosion of mesas. 

A broad ramp of sediment formed at the base of mountains when alluvial fans merge.

a gently sloping erosional surface cut into the solid rock of a mountain range in a dry region. It is usually covered by a thin veneer of gravel. Usually develops uphill from bajadas as the mountain retreats.

C. deflation

D. it is a great distance from the ocean

d. desert pavement

D. all of the preceding

D. low rainfall

False - The defining characteristic of a desert is low rainfall. It can be any temperature. Antarctica, which is cold and snowy, is a large desert because it recieves very little precipitation during the year. 

A flash flood has high runoff creating sudden local floods of high discharge over a short duration of time; normally dry beds become raging rivers after a thunderstorm. With average floods, they are more predictable and over a longer period of time, whereas with flash floods, they are fairly unpredictable, and over a short period of time.

• Humid regions have less change in air temperature while desert regions have a high variation in extreme temperatures, therefore the wind tends to be stronger in desert regions.
• Also, the sediment itself is easier to blow around because the lack of moisture means that it is less heavy and there is nothing concreting sediments together.

A desert is any arid region that receives less than 25 cm of precipitation per year.

• Most of the world's deserts are located in two bands around the world, one near latitude 30 degrees North and one near latitude 30 degrees South.
• In the global air circulation, air rises near the equator and cools creating a lot of preciptation and the tropical environments found there. This air then sinks again around 30 degrees north and south. As it sinks, it compresses and heats up, creating the dry, arid environments that create deserts.

Desert washes, or arroyos, are commonly steep-sided, with flat floors covered by loose sediments (a result of rare but highly erosive flash flood events).

flat-lying sedimentary rocks that are heavily eroded into plateaus, mesas and buttes.

Sand dunes are mounds of loose sand grains piled up by the wind. There are four common shapes for sand dunes, but many dunes cannot be classified and are very irregular.