The answer is relative dating.
There will be huge changes in an ecosystem
What is it called when lava cools and hardens? Sometimes magma flows upward and is forced out onto the earth's surface during a volcanic eruption. Magma that reaches the surface of the earth is called lava. When it cools and hardens, it too forms igneous rock. Igneous rock that is formed on the earth's surface is described as extrusive.n:
