Answer: D. It can melt to a depth of a few meters in summer, then refreeze in winter.
Explanation:
Permafrost is ground which remains frozen for two or more years. Permafrost consists of soil, rock and sand fused together by ice. Mostly found in areas in high altitude, the Arctic, Antarctica, it is common in periglacial environments where temperatures are below freezing
.
The topmost layer of permafrost can melt in summer and refreeze in winter. This thawing and refreezing produces a ground pattern called columnar joints similar to the one formed when molten lava cools.
Answer and Explanation:
Sediment transport occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting.
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One major way in which waves erode land is through the friction of the water on the land itself. Another major way is that the salt in the water erodes the land through chemical processes.
Answer: As altitude increases, atmospheric pressure decreases
Explanation:
Atmospheric pressure 
is defined as the force 
per unit area 
the air that forms the atmosphere exerts on the Earth's surface:
It should be noted that as the altitude increases less air is above and, therefore the air weights less. This is because the atmosphere losses density as we ascend, causing less air.
However, it is important to point out this decrease in pressure is not linear, since at the beginning (in the first kilometers above sea level) it reduces more rapidly than in the next kilometers above. That is why this relationship between atmospheric pressure and altitude is exponential.
