What is the difference between an environment and an ecosystem?

What is the border between layers a through f and layer g called?

The oldest seafloor in the atlantic ocean is located closest to the edge of the continents. explain how this age can be used to figure out when north america first began to separate from europe

The first atomic explosion was detonated in the desert north of alamogordo, new mexico, on july 16, 1945. what percentage of the strontium-90 ( yr) originally produced by that explosion still remains as of july 16, 2016?