How does chalk form?

A) evaporation of water in a lake or sea
B) accumulation of microscopic organisms composed of calcium carbonate
C) precipitation from seawater early in Earth's history
D) accumulation of silica-rich organisms or mixing of seawater and groundwater

Calcium Carbonate

A chemical compound with the formula CaCO3, found in rocks such as limestone, chalk, and marble, and is the main component of shells of marine organisms.

Chalk Formation

A type of limestone characterized by its fine, white, porous structure, formed from the accumulation of microorganisms' calcite shells.

Microscopic Organisms

Tiny life forms, not visible to the naked eye, including bacteria, protozoa, and certain types of fungi and algae.