More than 139,000 of those are active, pumping vast amounts of CO2 into the oceans
Lava contains a surprising amount of carbon dioxide, says consulting geologist Timothy Casey. In fact, CO2 is the second most abundantly emitted volcanic gas next to steam.
Carbon dioxide emissions from volcanoes – especially from underwater volcanoes – dwarf anthropogenic (man-made) contributions sources, says Casey.
Since seawater in the vicinity of hydrothermal vent systems is saturated with carbon dioxide, and since seawater elsewhere is not saturated with CO2, it stands to reason that this saturation came from the hydrothermal vent system, Casey argues.
In point of fact, says Casey, carbon dioxide escapes these hydrothermal vent systems in such quantities that it sometimes accumulates in submarine lakes of liquid carbon dioxide. There is nothing to prevent that superheated carbon dioxide from dissolving into the seawater or otherwise making its way to the surface.
As part of his argument, Casey points to a study by Hillier and Watts. After surveying 201,055 submarine volcanoes, they estimated that a total of 3,477,403 submarine volcanoes exist worldwide.
Of those 3,477,403 underwater volcanoes, Casey estimates that 139,096 are active.
More than 139,000 ACTIVE underwater volcanoes. No wonder CO2 levels are rising.
See Casey’s entire paper “Volcanic Carbon Dioxide.”
(Principia Scientific International, 16 June 2014).
Thanks to Hans Schreuder for this link
Hillier and Watts paper:
Hillier, J. K., & Watts, A. B., 2007, “Global distribution of seamounts from ship- track bathymetry data”, Geophysical. Research. Letters, Vol. 34, L13304, doi:10.1029/2007GL029874