We know that earth is bombarded by thousands of meteorites every day, none of which does our planet much damage. Any meteorite up to 10m (33ft) in diameter will normally burn up in the atmosphere before it reaches Earth, separating into tiny fragments. If a meteorite larger than this falls to Earth, it can cause considerable damage — impacting with the energy of five nuclear warheads. Approximately once every 1000 years, a larger meteorite does fall to Earth, and several large craters caused by such impacts can still be seen. One such was the nickel – iron meteorite that created the Barringer Crater in Arizona, USA. The meteorite was an incredible 45m (148ft) wide, creating a crater nearly 1.5km (1 mile) in width. However, it would take an impact by an object roughly 5km (3 miles) wide to cause mass extinctions and threaten life on Earth.
Most meteorites that are found on the ground weigh less than a pound. While it may seem like these tiny pieces of rock wouldn’t do much damage, a 1-lb. (0.45 kilograms) meteorite traveling upward of 200 mph (322 km/h) can fall through the roof of a house or shatter a car windshield.
When the Grimsby meteorite landed in Ontario, Canada in 2009, for example, it broke the windshield of an SUV. In another incident, meteorites crashed into the back end of a Chevy Malibu in Peekskill, New York, in 1992, Cooke and Moorhead said. Thankfully, no one was injured during these events.
However, the pieces of rock falling from the sky are not even the greatest concern regarding meteor impacts, Cooke said.
“What causes the most damage is the shock wave produced by the meteor when it breaks apart in [Earth’s] atmosphere,” Cooke said. “So, you don’t have to watch for the falling rocks — you have to worry about the shockwave.”
For example, the Chelyabinsk meteor — an asteroid the size of a six-story building that entered Earth’s atmosphere in February 2013 over Russia — broke apart 15 miles (24 km) above the ground and generated a shock wave equivalent to a 500-kiloton explosion, Cooke said. It injured 1,600 people.
Another major collision was the Tunguska meteorite, which was larger than Chelyabinsk and 10 times more energetic. The meteorite exploded over the Tunguska River on June 30, 1908, and flattened 5000,000 acres (2,000 square km) of uninhabited forest. Because of its remote location, the event is an example of a meteorite that would have gone undetected had it not been so large, Cooke and Moorhead explained.
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