What Happens When Meteorites Hit?
What happens when a meteorite hits has not been directly observed by scientists. However, close examination of impact craters has given them quite a few clues about the process. Meteorites that do not burn up in the atmosphere produce an impact crater, throw dust into the air, and send shock waves through the air and ground. Large meteorite impacts are thought to be responsible for causing climate changes that led to mass extinctions.
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Impact Craters
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When a meteorite hits the surface of the Earth, it deforms the ground and sends a shower of loose soil and debris up into the air, which eventually falls back to the ground. In only a few seconds, the rocks at the point of impact melt and even partially vaporize. An impact crater, a circular depression with a raised edge, is created. Impact craters range from a few feet to many kilometers in width, such as the Barringer Meteor Crater near Flagstaff, Ariz..
Shock Waves
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At impact, shock waves are generated in the meteorite, the ground, and in the surrounding air. As the shockwaves travel through the ground, they produce earthquakes. Scientists think that earthquakes as violent as 13 on the Richter Scale would be possible with larger meteorites. Shock waves travel through the air as sound waves, producing explosions so loud that they may be heard many miles away.
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Size of the Meteorite
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Both the size of the meteorite and its velocity affect the amount of impact that the meteorite produces when it hits Earth. Micrometeorites are so small that they totally vaporize before they reach the Earth's surface. Small meteorites of about one to two inches (two to three centimeters) may only partially vaporize as they fall, which means they will survive to strike the surface. But they are small enough not to do any damage on impact. Meteorites with sizes of a kilometer or more are considered large enough to have a catastrophic effect on the Earth but are rare.
Effects on Earth's Climate
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Large meteorite impacts could throw so much dust up into the atmosphere that the amount of sunlight reaching the Earth's surface would be drastically reduced. The dust could remain in the air for months. The reduced sunlight would cause the both the air and Earth's surface to cool, producing winter-like conditions throughout the world. Plant growth would be severely affected, and food crops could fail.
Fire and Rain
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Meteorites can cause plants to catch on fire. Wildfires would run rampant, throwing additional smoke and dirt into the atmosphere. Meteorite impacts in the ocean or even large lakes could produce huge amounts of steam. Increased amounts of carbon dioxide and water vapor, which are both greenhouse gases, would offset some of the cooling from dust and cause a warming trend.
Mass Extinctions
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Scientists theorize that meteorite impacts may be possible for some of the mass extinctions that have occurred on the Earth. The mass extinction at the end of the Mesozoic Era, 65 million years ago, is thought to have been responsible for the extinction of almost half the species alive at the time, including the dinosaurs.
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References
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- Photo Credit meteor strike 18 image by chrisharvey from Fotolia.com
