How Is the Carbon Cycle Involved in the Rock Cycle?

The Rock Cycle

• 1

  The rock cycle is a series of changes that describes the distribution of rocks on the earth's surface, their reactions to erosion and weathering, and their eventual return to the earth's mantle through tectonic subduction. The geological carbon cycle partially overlaps the rock cycle through the erosion and subduction of carbon-bearing minerals and the eventual reintroduction of that carbon through volcanic eruptions.

• 2

  Carbon enters the geological carbon cycle when carbonic acid in the atmosphere bonds with minerals in the earth's crust to create various carbon-based rock, most notably limestone (calcium carbonate). This carbon-bearing rock is eventually washed into rivers by the natural processes of weathering and erosion, where it is carried to the ocean along with all the other dissolved minerals.

• 3

  Once they have reached the ocean, the carbon-bearing minerals sink slowly to the bottom of the sea, where they become part of the sediment covering the abyssal plains. The abyssal plains are enormous stretches of flat terrain forming the center of tectonic plates. Since abyssal sediment is beyond the reach of most natural processes, it remains inert until continental drift brings it to a subduction zone, an area where one tectonic plate is sliding beneath another and returning to the semiliquid mantle.

• 4

  When carbon-bearing minerals in the abyssal sediment are subducted, the heat and pressure separate the carbon from the minerals it has bonded to, returning it to a gaseous form. This carbon remains locked within the earth's mantle until it is returned to the surface in the form of a volcanic eruption and re-enters the atmosphere, ready to begin the carbon cycle again.