They have been slowly recycled over millions of years.This is called the rock cycle.Sedimentary rocks form when tiny particles of rock that have been weathered and eroded settle out of slow moving ...

Almost all fossils are preserved in sedimentary rock. Organisms that live in topographically ... formed and recycled into other types of rock in a process called the “rock cycle.” This makes the rock ...

The study of nitrogen isotopes—different forms of the element with varying atomic weights—has shed light on early Earth's nitrogen cycle. Researchers analyzing ancient sedimentary rocks have ...