Some of the oldest rocks ever found have been estimated to be about 3.5 billion years old. Is it likely that these rocks were present when Earth was first formed?
a. No, rock material is constantly recycled on Earth as rock is melted into magma.
b. Yes, most of the rocks on Earth can be dated back to the time when Earth was first formed.
c. No, this rock is probably just a sedimentary rock that was formed by much younger igneous rocks.
d. No, it is likely that any rocks older than a few hundred years are meteorites from outer space.