One volcano, or one magma release, is indeed a “spit in the ocean”. But counting all the volcanic releases this planet has undergone in the last couple of billion years, adds up to an awful lot of spit. Probably, heat releases through geothermal superheating of liquid water, and a geyser eruption, accounts for more transfer of energy from the deeper reaches to the atmosphere than magma release.
But remember magma release is what built a lot of the mountain chains, and is still a factor in creation of islands in the sea, similar to how Hawaii was formed.
The heat balance of the earth is moderated by how much is radiated away during the night (earthshine), on the side of the world turned away from the sun, as compared to how much is absorbed by absorption of radiation from the sun on the side in daylight. This could probably be calculated, or at least a SWAG number could be put down for it, but it would involve a lot of factors, some of which seems not to have been considered by the “global warming” prophets.
Actually, an additional factor in the heat balance of the earth is the production of heat by nuclear forces in the earth’s interior. The heat loss was a big unsolved question to scientists and mathematicians until nuclear energy was discovered.
Barringer Crater in Arizona was 50,000 years ago. Anyone have information on effects from that? Toba caused a bottleneck in population that I read was as few as 5 to 10,000 humans.
Llaima is one of Chile’s two most active volcanos (the other is Villarrica). It had at least 32 VEI 3 eruptions in the 20th Century, the last in 1988. It had a VEI 4 in 1640 (VEI=Volcanic Explosivity Index). [Source- “Encyclopedia of Volcanoes”, Sigurdsson, 2000]