Earth’s natural long-term carbon cycle removes carbon dioxide (CO2) from the atmosphere through weathering, a chemical reaction that occurs between volcanic rock, CO2, and water.
The cycle, which normally takes millions of years, involves rain interacting with CO2 and breaking down rocks, which are then transported by rivers into the ocean for use in shells and corals.
Without this carbonate-silicate cycle of water interacting with volcanic rocks to remove CO2 from the atmosphere, Earth would look like Venus.
Accelerated Rock Weathering Can Work To Remove CO2 Levels On a Global Scale
The Last 3 Ice Ages Were Influenced By Increased Volcanic Rock Weathering Near the Equator
Over geological timescales, CO2 levels and the temperature of the climate are regulated through the exposure and weathering of volcanic rock, especially near the equator. Weathering has a stabilizing effect, so as the planet gets hotter from increased CO2, weathering rates increase and CO2 is more rapidly removed. For this reason, weathering is referred to as the “global thermostat.”
A paper published in the April 20196) issue of Science, adds to the accepted body of evidence that the last 3 ice ages were caused by the exposure and weathering of volcanic rock near the humid tropics.
The accompanying gif and graphs show how volcanic rock exposed near the equator correlates with increases in planetary ice cover.
Starting around 50 million years ago (Ma), as the Himalayan Plateau begins to rise, so too does ice cover. Observe how, as volcanic rock (orange) becomes present near the equator (green), ice coverage begins to increase (blue).
On geological timescales, nearly all of the weatherable rock on Earth that is exposed has already weathered and built up a coating on it that inhibits the weathering reaction. Other forces such as landslides, glacier melt, etc can expose new weatherable rock, but if it is stationary, the weathering reaction will slow down soon thereafter.