Maria over at Green Gabbro feels that I have printed a false and malicious post for the purpose of defaming volcanoes. I cannot be held liable if the accusations are true. Maria thinks that printing a list of “all the good things volcanoes do” will be more than sufficient to make up for their previous indiscretions. But perhaps we need a bit of perspective on the role of volcanoes in the history of life.
According toWignall’s excellent review in 2001 on why and how volcanoes are evil, 6 of the 15 major extinctions in the history of life coincide with major episodes of volcanicity. In the last 300 Ma, all extinctions coincide with large igneous deposits.
How did volcanoes do it? Wignall provides this wonderful diagram (click for larger) based on the chain of events occurring in conjunction with the Siberian Traps (a large eruption event ~250Mya).
Of course some of Maria’s list is also suspect.
- Volcanoes also flux out CO2, which keeps us warm and cozy. Or they cause considerable global warming which leads to oceanic stagnation and marine anoxia that ultimately kills everything. But let’s not dwell on the negatives.
- Ditto other volatiles. Do you want to try life without volcanic sulfur? I don’t either.Sure sulfur can come from volcanoes. But anaerobic bacteria can produce the same from sulfate minerals. These deposits are so large they are good enough for commercial sulfur production in US, Poland, Russia, Turkmenistan, and the Ukraine. I’m no geologist but I am also pretty sure that sulfate, the major form of sulfur in the oceans, can also come from the weathering of continental rocks.
- Volcanoes created the continents (and islands). Without continents, there would be no primeval life-cradling tide pools. Also, we would be mermaids.With no volcanoes the whole world would be an ocean. Sounds good to me! What makes you think the primordial ooze was so close to land?
- Submarine volcanoes provide a source of energy for all manner of exotic salty friends.Sure there a few hydrothermal vent organisms scatter along the ocean bottom. But there are far more who don’t need the vents. Helping a few species will not mitigate killing off millions!