Exogenic disasters – impact event
Exogenic phenomena refer to any external processes or events in space that effect the earth, from the radiation of the sun, to the magnetic force of the moon producing the ocean tides, to meteoroid impact events.
Impact events occur in the collision of meteoroids, asteroids or comets with the earth. The biggest event detected so far, is the giant Chicxulub Crater with a diameter of 180 km (eventually with a second external ring with a diameter of 300km) underneath the Yucatan peninsula in Mexico, discovered in 1990. Scientists suggest that about 65 million years ago, a meteorite with a diameter of 10 km hit the earth, causing tremendous tsunamis and emissions of dust. The cloud of dust that covered the atmosphere several years, produced climatic and environmental changes, and is the most likely cause for the extinction of the dinosaurs.
The most significant eye-witnessed earth impact is the Tungunska event in Siberia in 1908, where an explosion of a meteorite six-to-ten kilometers above the earth’s surface caused an enormous blast of energy. It devastated an area of 2.150 km2, felling approximately 60 million trees. The force of the explosion is estimated to equal that of 10-to-15 tons of TNT, which is 1150 times more forceful than that of the atomic bombs hitting Hiroshima. Eyewitnesses report a blueish light moving across the sky, followed by lightning, heat, thunder, shattering of the earth and a shock pressure wave that knocked down people and shattered windows hundreds of miles away.
Smaller earth impacts occur more often, often without even being noticed. For example in 2000, a meteor with a diameter of 4,6 m exploded over Yukon in Canada at an altitude of 26 km, lighting up the night and with its electromagnetic pulse and collapsing of one third of Yukon’s electrical power grid.
A major impact in the 21st century is estimated with a probability of 1 in 6000.