Chalk forms from _________.
A) magnesium rich fluids that chemically alter limestone bearing reefs
B) direct precipitation from seawater
C) evaporation of magnesium rich waters
D) the hard parts of microscopic organisms that accumulate on the sea floor

Question

Quizplus · Accepted Answer

Chalk is primarily composed of the calcite skeletons of microscopic marine organisms, such as foraminifera, as well as the calcareous plates of algae, known as coccoliths. These organisms live in the upper part of the ocean. When they die, their calcareous remains sink to the bottom and accumulate, forming chalk deposits over millions of years.

Chalk Forms from _________