It depends on the map. There should be a key indicated.
The position of the sun in the sky
I think the second one since the largest bar (?) is for infants meaning that the population is mostly 4 year olds. Hopes this helps!
That would just be called Weathering and Erosion. Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity. Mechanical weathering physically breaks up rock. One example is called frost action or frost shattering. Water gets into cracks and joints in bedrock.
