Which is more devestating to the planet - 1.1 Billion cars constantly spewing carbon or a volcano?

Cars, by far.

On an annual basis, humans emit more than 100 times more CO2 than volcanoes.

http://volcanoes.usgs.gov/hazards/gas/index.php

Cars account for about 10% of human CO2 emissions.

http://cait.wri.org/figures.php?page=World-FlowCha...

Therefore car emissions account for over 10 times more CO2 than all volcanoes, let alone one single volcano.

As for other impacts, volcanoes have a very powerful but very localized impact from their magma and ash emissions. But on a global scale, CO2 impacts dwarf these mostly localized impacts.

The volcano, or at least a very large volcano, could have a huge devastating effect on the planet, but it is unlikely to have a significant impact on other than a very small sector of the world population. Volcanos have been errupting for billions of years and volcanic action has been largely responsible for the face of the planet as we see it today. Cars, on the other hand, have only been around for a hundred years, and although they may not have changed the planet that much they have certainly had a devastating effect on the people who live on it and the air we breath.

The cars spew more carbon but volcanos can be much more destructive to life. If (when) Yellowstone goes off, for example, it is likly that a billion people or more will be killed, and the earth will be plunged into a volcanic winter for at least a couple years. The most a car could do would be releasing CO2 which should do no more than moderate the climate.

Volcanoes only put out a small fraction of the amount of greenhouse gases that humans do. All the volcanoes on land *together* only put out 300 million tons of CO2 per year - about one hundredth of human output.

http://www.newscientist.com/article/dn11638

Icarus, you need to look at the Mt. Pinatubo eruption from the 1980s. The one quote that I remember is that the eruption put more gas and particulates into the atmosphere in a week than mankind has since they have been recognized as Homo sapiens.

Neither. Oceans are the main producer of CO2.

Scientists are now discovering that CO2 is not the cause of warming.

A volcano

Both produce lots of CO2 , but the plants must have CO2 to live.

both of course

volcano is a natural thing.. cars are not..