While volcanoes are not quite as common as weather problems when it comes to natural disasters, they can cause more devastation than most of the other forces on the planet that occur naturally (http://en.wikipedia.org/wiki/Vulcanism). A volcano not only destroys everything in it’s path, but also destroys most of the life that is anywhere near it due to the heat and the ash. A great example of this is the ancient city of Pompeii, where a major volcanic eruption occurred so swiftly that an entire major city was engulfed and thousands of people perished immediately. When Pompeii was discovered and the empty “shells” where people were incinerated were filled, it gave the world a view of what would happen if there was to be an eruption of a large proportion that happened so swiftly that no one had time to get out of the way. This discovery has led to many different doomsday theories involving volcanoes.
Some of the effects of a volcano on the Earth will vary with each different volcano. But the gasses alone that are released when any type of volcano erupts contribute to many problems around the globe. Water vapor is one of the most common gasses that are released when one erupts, then carbon dioxide, and then sulfur dioxide – all of which can be deadly to humans and other living things in the area. Hydrogen sulfide, hydrogen chloride, and even hydrogen fluoride are other gasses that are released and can wreck just as much havoc on the Earth and the atmosphere as the other, more abundant gasses. When these gasses are released, they are usually shot straight up into the air, somewhere between 10 and 20 miles into the atmosphere, and are carried all over the surrounding area, and sometimes even the globe if the scale is big enough. If there are enough of these gasses released, this can cause the temperature on the Earth’s surface to drop drastically, with can be devastating for living things in and around the volcano.
Volcanoes also emit aerosols that damage the ozone layer and other areas of the atmosphere and the Earth itself, so if one were large enough, like a super volcano that scientists have been predicting, these emissions could cause a global meltdown of the climate and the atmosphere. These aerosols and gasses also contribute to acid rain, another factor that would cause serious problems if released all around the world.
A “super volcano” is a huge volcano that has a monstrously large caldera that can produce an eruption that would cause devastation on a global scale (http://en.wikipedia.org/wiki/supervolcano). An eruption from a super volcano would cause a major temperature change that would cool off the Earth to the point of freezing, and probably usher in a new ice age since the ash that would be expelled from one would completely block out the sun for many years to come. A super volcano is considered to be the most dangerous of any volcano due to it’s size and the possible problems that would arise from an eruption of one and the fact that it is virtually impossible to determine just how large an eruption would be since there is no real way to measure how large the caldera is underneath the Earth’s surface. Some great examples of supervolcanoes that have large calderas are Yellowstone Park which holds the Yellowstone Caldera and Sumatra, Indonesia which holds Lake Tobe.