5. During the most recent ice age, 30% of the Earth's surface was covered by glaciers.
The reason why such a large amount of glaciers formed was due to the extremely low temperatures that lasted for extended periods of time. These temperatures prevent snow from fully melting in certain areas; instead, the bottom layer of snow simply turns to ice. Because the ice is now on the ground, it starts to form a mound, which becomes a glacier. The snow piles on top of the mound of ice, and the force of the accumulated snow compresses to become increasingly solid. Eventually, it takes the form of a glacier, and inside, its solidity traps the moisture from the Earth. The moisture turns to ice, because it cannot evaporate, which serves to cause growth of the ice beneath the standing glacier. These glaciers become "ice sheets" which are continental glaciers, which are the reason for the vast area covered by glaciers during the last ice age.
7. Dry, flat lake beds located in the center of basins in arid areas are called PLAYAS.
Playas are formed when water evaporates from a lake or basin, leaving only minerals, called evaporites, sometimes making the soil into silt. Still, the lack of water results in the area staying barren of plant or animal life.
8. A cone of debris deposited by running water at the mouth of a canyon in an arid area is known as an ALLUVIAL FAN.
Alluvial fans are formed when water and sediments, sometimes debris, travel through a slim gap, by means of water, between land masses, such as hills or mountains, then gradually flows into a more open space and a less steep slope. It's like the top of the slide the gives momentum for the rest of the way down.
9. RUNNING WATER is the force that causes most of the erosion in desert areas.
Rainwater, and the runoff from it, causes erosion very quickly is dry areas like the desert. Wind also causes erosion, but it is primarily rain.
10. CHEMICAL WEATHERING causes the rust-colored tint of some desert landscapes.
Chemical weathering is the process of rainwater reacting with minerals and rocks, often this can result in oxidization, which the rust-colored tint of some deserts can be attributed to.
11. PHYSICAL WEATHERING is the main type of weathering in deserts.
Physical weathering is a process where things break down without changing their chemical composition. As time passes, movements of the Earth and other factors cause materials to wear away. Because it takes longer, it does not cause as much erosion as chemical weathering caused by rainwater; still, physical weathering is always happening, whereas chemical weathering is not. For this reason, physical weathering is the main type of weathering in deserts, even if it isn't the most effective.
12. The weathered debris in deserts consists mainly of UNCHANGED ROCK and MINERAL FRAGMENTS.
The reason the answer is "unchanged rock" is because "changed rock" refers to that which has been subject to a chemical reaction. "Changed rock" will completely erode before long, so it is not likely to be debris. As for mineral fragments, that is the parts of the rocks that have eroded.
14. When wind creates a sand dune, the sheltered side of the dune IS STEEPER THAN THE WINDWARD SIDE.
This is because the wind blows sand, which builds up on the windward side, creating a hill. The opposite side is not receiving the wind, at least not as much; therefore, the force of the wind is pushing harder on the other side, causing it to tilt toward the sheltered side—which naturally results in a steeper slope.
16. Dunes whose tips point into the wind are called PARABOLIC DUNES.
Basically, parabolic dunes got their name because they are shaped kind of like a semi-circle (or a parabola). The top tilts toward the direction from which the base of the dune leans away from.
17. The shape of star dunes is mostly due to VARIABLE WIND DIRECTIONS.
When the when isn't going one direction, dunes will not lean one way or another; the result is star dunes.
Hope this helps!
