Where and in what form does carbon enter long-term stores?

Answer 1

When living things die and end up in anaerobic conditions :

(trees falling into swamp water)

which leads to peat bogs and finally to coal.

Answer 2

Carbon enters long-term stores primarily through the process of sedimentation in oceans and lakes, where it gets trapped in organic-rich layers of sediments. Over time, these sediments can become buried and compacted, eventually forming sedimentary rocks like limestone, shale, and dolomite. This process locks up carbon in the Earth's crust, where it can remain stored for thousands to millions of years.