Billions of years ago, Earth's atmosphere was composed primarily of carbon dioxide. Where might one go on Earth to find a large fraction of this carbon dioxide today?

Question

Quizplus · Accepted Answer

The carbon dioxide from Earth's early atmosphere is now largely found in sedimentary rocks, such as limestone. Limestone is composed primarily of calcium carbonate (CaCO3), which forms from the carbon dioxide that was once in the atmosphere. This process involves the absorption of CO2 by ocean water, the formation of carbonate compounds by marine organisms, and the eventual deposition and lithification of these materials into limestone and other carbon-bearing sedimentary rocks. Mountain ranges like the Rocky Mountains contain significant amounts of limestone, representing a major reservoir of the Earth's carbon.

Billions of Years Ago, Earth's Atmosphere Was Composed Primarily of Carbon