Craters

Want to stay on top of all the space news? Follow @universetoday on Twitter

Craters are holes in the ground, usually covering vast areas. They can be caused by any of the following: a celestial body impacting another, volcanic activity, an underground explosion such as one caused by a nuclear weapon or a phreatic eruption, a sinking of the surface, or simply an explosion near the surface.

Craters formed by celestial bodies are called impact craters. One such crater is Meteor Crater, also known as Barringer Crater. For a long time, this impact crater was believed to have been caused by volcanic activity. However, after further study (after the initial suggestion and subsequent insistence of Daniel M. Barringer), it was later found out that it was caused by a meteor.

Volcanic activities can also form craters. In such instances, the craters are simply called volcanic craters or calderas. Volcanic craters, which usually come in the form of circular depressions, have very similar appearances to impact craters. The craters are usually formed when a volcanic eruption empties the volcanoes magma chamber, consequently causing the area above it to collapse.

Underground explosions, which form cavities there, also force the ground above it to collapse. Explosions caused by nuclear weapons (such as those in the Nevada Test Site) are known as subsidence craters. On the other hand, if the explosion is the result of groundwater interacting with hot lava or magma, then the resulting crater is called a maar.

If the explosion that caused the crater is above, at or just below the surface (i.e., at a shallow depth), then the crater is aptly called an explosion crater. Such craters may have been formed by bombs dropped by military planes or explosives planted near the surface.

Due to their possible cataclysmic connotations, impact craters are among the most intriguing – and arguably the most intimidating. Looking at the largest ones left here on Earth can remind us of the devastation that the objects that formed them can cause. 65 million years ago, these objects may have wiped out the mighty dinosaurs.

Some of the largest impact craters on Earth are South Africa’s 300-km-wide Vredefort, Canada’s 250-km-wide Sudbury, Mexico’s 170-km-wide Chicxulub, and Russia’s 100-km-wide Popigai. Looking at the sheer size of these craters can make anyone shudder.

Just by looking at the craters on the Moon should give us an order-of-magnitude idea how many craters may have impacted the Earth in the past.

Here’s a list of popular craters on Earth from Universe Today.

Come October 9, 2009, LCROSS will perform a lunar impact. Find out which crater NASA has chosen for the impact. If you want to know more about the largest crater on the Moon, NASA’s got the right stuff.
There are some interesting episodes from Astronomy Cast that we’d like to recommend:
The Source of Atmospheres, the Vanishing Moon, and a Glow After Sunset
The Moon, Part 1

Reference:
NASA

Tagged as: asteroid, asteroid impact, craters, Meteor Crater, meteoroid impact