When the sea was formed

　The oceans formed within a few hundred million years after the birth of the Earth. The ocean floor was covered with basaltic (CaSiO₃), which gradually dissolved to provide Ca²⁺ to the seawater. Carbon dioxide absorbed into the ocean from the atmosphere reacts with Ca²⁺ and is accumulated as calcium carbonate particles. This reaction is summarized below.

CaSiO₃ + 2CO₂ + H₂O 　→ CaCO₃ + CO₂ + H₂O + SiO₂

(From the birth of the earth to the time when there were no continents)