Chalk is a soft, white rock that is formed from the accumulated skeletons of tiny marine organisms called coccolithophores. These single-celled algae have hard, calcium carbonate plates called coccoliths that form their external skeleton. Over millions of years, these coccoliths accumulate on the ocean floor, eventually forming chalk.
Here are some other possibilities:
* Diatom ooze: Diatoms are another type of single-celled algae that have silica (glass) skeletons. When these diatoms die, their skeletons accumulate and form diatom ooze, a type of sediment found on the ocean floor.
* Foraminifera: These tiny marine organisms have shells made of calcium carbonate. Their shells can also accumulate to form sediment layers.
Let me know if you have any other questions!