Quiz 10.2

Deflation: (3 answers are correct)

... may result in the build up and formation of desert pavement. ... is the lowering of the land surface by the removal of sediment by wind. ... may produce a blowout.

Most desert streams are ephemeral because:

... they exist only during and shortly after a rain event.

The number one erosional agent in a desert is wind.

False.

Which five statements are correct regarding this aerial photograph? The white linear pattern on the left side of the image is snow capping the mountains.

If the green areas in this image are shallow bodies of water, they are known as playa lakes. The long white linear band that runs from top to bottom of the photo is a salt flat on the valley floor. The salt flat forms as playa lakes evaporate and the dissolved salts in the water are precipitated out. Immediately to the left of the salt flat are a series of coalescing alluvial fans forming a bajada. The semi-circular shape(s) on the right side of the white region (is an/are) alluvial fan(s).

Which four statements below are true of dust storms?

If undisturbed by other forces such as migrating sand, little dust is raised by blowing wind. Dust storms may travel for hundreds of miles. The Sahara is the largest source of dust storms in the world. Dust storms are mostly comprised of silt.

Which four statements below are true about loess?

Loess is a deposit of windblown silt from a dust storms. Loess is easily eroded. Loess is principally derived from deserts or glacial outwash. Loess forms some of the most fertile soil in the world.

Which three statements below are correct regarding this map?

Many steppe regions border deserts. Many deserts are located near the Tropic of Cancer and Tropic of Capricorn. The Sahara is the biggest desert on earth.

Which two statements are true regarding sand migration in a desert?

Most windblown sand travels in a jumping fashion called saltation. Most windblown sand travels close to the ground.

Which three statements are true regarding rainshadow deserts?

Rainshadow deserts occur downwind of topographic highs. The Great Basin desert is a rainshadow desert. The Sierra Nevada Mountains serve as a barrier for moist Pacific air traveling any further east because as the air lifts going over the mountains, it cools resulting in precipitation because cold air cannot hold as much moisture as warm air.

Which three statements are true regarding low latitude deserts?

The equator is a region of rising air creating low pressure. 20o to 30o north or south of the equator are zones of high pressure where cold air sinks resulting in little rainfall. Rising masses of air result in low pressure and abundant rainfall, as seen along the equator.

Which four statements are true regarding this image? (alluvium mountainous range)

The image is showing alluvium (stream deposited sediment) collecting along the mountain front. The alluvium is being deposited in "fans" (semi-circular deposits) at the mouth of the stream valleys. The sediment was brought down and deposited by ephemeral streams in the mountains. Where the alluvial fans coalesce they form a blanket of sediment along the mountain front referred to as a "bajada".

Which three statements below are true regarding this image? (dune diagram, long and stripey)

These are longitudinal dunes. This type of dune can grow to heights of several hundred feet. These dunes may grow many tens of miles in length.

Which three statements below are true regarding this image? (parabolic dunes, near a coast)

These are parabolic dunes. These dunes are commonly found along coasts. Unlike barchans, these dune tips point into the wind.

Which two statements below are true of these dunes? (barchan dunes)

These dunes are barchans. These dunes form on a hard ground with limited sand supply.

Which three statements are true regarding this image? (bunch of rocks and pebbles)

This image is showing desert pavement. This sediment has become concentrated on the desert floor because finer-grained sediments have been blown away. This sediment will serve to protect against further deflation.

Which three statements are true regarding this rock? (geometric rock in the sand)

This rock has been wind-sculpted and is called a ventifact. This rock has been polished and sculpted by sandblasting. If the rock has never been rotated, it is apparent that the wind has blown from more than one direction.

Which three statements are true regarding this image? (sand flow down a sand hill)

This sliding sand may produce cross-bedding. The sand is sliding to the angle of repose. The sand is sliding down the slip face of the sand dune.

Because the Basin and Range Province has interior drainage, the valleys are filling up with sediment weathered from the surrounding mountains.

True.

Due to the lack of moisture, the dominant type of weathering in a desert is mechanical.

True.

Yardangs are wind-sculpted landforms that generally contain sharp, elongated ridges.

True.