Geochemistry Question:

Igneous rocks are formed through volcanic action and because of volcanic activity.
Sedimentary rock takes a long time to form and is dead bits of animals laid down in the sea and compressed over millions of years to form rock; anywhere you see sedimentary rock you are seeing the remains of creatures that were once in the ocean a long time ago.
Metamorphic rock is formed through a combination of heat and pressure inside the earth.