Which two processes contributed to the reduction of carbon dioxide in the atmosphere before life on Earth?

The processes that contributed to the reduction of carbon dioxide in the atmosphere before life on Earth primarily involved the natural cycling of carbon through geological and physical processes.

Dissolving in oceans refers to the phenomenon where carbon dioxide from the atmosphere dissolves in ocean water, forming carbonic acid and leading to reactions that convert CO2 into carbonate ions. This process is significant because ocean waters can store large amounts of carbon.

Precipitation as sediments refers to the formation of carbonate sediments that can occur when dissolved carbonates precipitate out of seawater, eventually contributing to sedimentary rock formation. This long-term storage of carbon in sedimentary rocks effectively reduces the amount of carbon dioxide in the atmosphere.

These combined actions play a critical role in regulating Earth's carbon cycle and climate, providing a means for atmospheric carbon dioxide to be sequestered in solid forms over geological timescales.