Question

Why can't we study sedimentary rocks that are older than about 3.7 Billion Years Old (byo)?

A. Rock older than 3.7 billion years has too much graphite for it to be considered sedimentary.

B. We do! There is lots of sedimentary rock that is older than 3.7 byo, for instance, 3.8 byo rocks in Hudson Bay, Canada.

C. The earth was not stable enough for life until about 3.7 byo meaning sedimentary rock could not form until then because of a different carbon ratio.

D. There is very little, if any sedimentary rock that old because the lithosphere of the earth (the crust) is being continuously recycled and rock older than 3.7 byo has been subducted.

Answer 1

Sedimentary rocks are formed when sediment is deposited out of the air, ice, wind, gravity, or water flows carrying the particles in suspension. This sediment is often formed when weathering and erosion break down a rock into loose material in a source area.

D. There is very little, if any sedimentary rock that old because the lithosphere of the earth (the crust) is being continuously recycled and rock older than 3.7 byo has been subducted.