In shaft mining, only a very small area (The opening to the mine) is affected. By contrast, digging up all the soil and rock across a broad area of the earth's surface is very harmful to the environment.
In a rocket, burning fuel creates a push on the front of the rocket pushing it forward. This creates an equal and opposite push on the exhaust gas backwards
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.
