Question

How does limestone change throughout the rock cycle?

Answer 1

Limestone usually starts in the biosphere, gets recycled into the lithosphere or geosphere, moves to the atmosphere then back to the biosphere.

Explanation:

Most limestones actually start as calcium carbonate mud or shells precipitated by organisms in reefs or shallow shelf regions - the biosphere.

Lime mud gets buried by overlying sediments over long periods of time and turns into limestone. Limestone in the oceans gets dragged to subduction zones where it gets recycled into the mantle (geosphere),

Over time, the limestone is broken down into its chemical parts and may come back to the surface as volcanic `"CO"_2` (in the atmosphere). From the atmosphere, the `"CO"_2` might again become part of the biosphere by molluscs or corals absorbing the `"CO"_2` to help make their shells.