Schematic diagram showing the main sources and sinks for volcanic CO2 on Earth within the geological carbon cycle. CO2 is released at MORs during crustal genesis, but it is also absorbed into the newly formed crust in high temperature hydrothermal reactions. Carbonates precipitate directly into oceanic crust and collect in sediments before the subducting slab is carried under the mantle wedge. Volcanism then produces CO2 emissions from the fore-arc (through cold seeps), arc volcanism, rift volcanism, intra-continental volcanoes and hotspots. The CO2 emitted into the atmosphere reacts in weathering reactions with silicate rocks, carrying C back into the ocean where the geological carbon cycle is eventually closed through carbon sequestration into the subducting slab material.