Answer: The release of methane from thawed permafrost
Explanation:
With increasing global warming, permafrost in the arctic is melting. The carbon and methyl clathrates present in permafrost escape into the atmosphere to form carbon dioxide and methane, both greenhouse gases.
In the Arctic, molecules of methane are trapped in ice crystals as methyl clathrates. When the temperature increases, these crystals release methyl clathrates which become methane when in contact with the atmosphere.
The cause of the increasing atmospheric 
is due to the the thawing of dead organisms present in the permafrost. As the permafrost melts, these organisms decay and release into the atmosphere.
Answer:
Climate Change
Explanation:
Some of the biggest human migrations coincided with major changes in climate, according to a new analysis. Researchers say early humans set out in search of climates where food was available. And some populations stayed put in certain locations because barriers like glaciers block their progress.
Answer:
As you maintain height, the amount of air above you reduces, lowering the pressure. When the pressure drops, the air molecules spread out more (air expands) and the temperature decreases
Explanation:
Not sure if its long enough.
Tension is created when 2 tectonic plates diverge
