Volcanoes are also part of the extended carbon cycle . Over very long ( geological ) time periods , they release carbon dioxide from the Earth 's crust and mantle , counteracting the uptake by sedimentary rocks and other geological carbon dioxide sinks . The US Geological Survey estimates are that volcanic emissions are at a much lower level than the effects of current human activities , which generate 100 – 300 times the amount of carbon dioxide emitted by volcanoes . A review of published studies indicates that annual volcanic emissions of carbon dioxide , including amounts released from mid-ocean ridges , volcanic arcs , and hot spot volcanoes , are only the equivalent of 3 to 5 days of human-caused output . The annual amount put out by human activities may be greater than the amount released by supererruptions , the most recent of which was the Toba eruption in Indonesia 74,000 years ago
Toba eruption
Toba catastrophe theory
Climate change