Temperate areas which experience few extremes of weather and climate tend to be more attracted than areas which experience extremes. Areas which have rich, fertile soils allowing successful agriculture tend to have higher population densities than areas which have poor quality soils have sparse populations.
Dune deflation hollows are where wind has removed sand down to a level where a layer of particles too heavy for the wind to move (an armoured surface) stabilises the sand and prevents the surface being lowered further.
A crevasse is a deep, wedge-shaped opening in a moving mass of ice called a glacier. Crevasses usually form in the top 50 meters (160 feet) of a glacier, where the ice is brittle.
a mass of rocks and sediment carried down and deposited by a glacier, typically as ridges at its edges or extremity.
