The Tunguska Event

Though it flattened all the trees in every direction for 30 miles, the airburst that took place over Siberia's Tunguska River left no crater behind. Scientists theorize that the blast, caused probably by a meteor or comet fragment that exploded a few miles over the surface of the Earth, was 1000 times as powerful as the bomb that fell on Hiroshima, Japan.

Otherworldly Object

It is believed that the Willamette meteorite crashed to the Earth somewhere in Canada, but that it was shifted by a glacier south to Oregon, where it was discovered in 1902. It is the largest meteorite found in the United States, and the sixth largest in the world.

Impact Crater

Gosses Bluff, near Alice Springs, Australia was formed by the impact of a meteor or comet about 143 million years ago. It is one of the approximately 170 terrestrial impact craters on the Earth's surface.

Hole in the Desert

Much smaller and younger than Gosses Bluff, Arizona's Meteor Crater is also known as Barringer Crater, in honor of Daniel Barringer, the man who first suggested it was formed by the collision of a meteor with the Arizona desert around 50,000 years ago.

Curiosity

Two Saudi men examine a two-ton meteorite embedded in the sand of the Kingdom's desolate Empty Quarter.

Meteor Shower

A time-lapse photograph captures the trails of two meteors in the sky over Amman, Jordan. The red streaks at the mid left and bottom right are meteors; the white streaks are stars. Most meteors disintegrate in the intense heat created from entering the Earth's atmosphere.

Ring Shaped Reservoir

Water from a series of hydroelectric projects has filled Manicougan Crater in northern Quebec to brimming. The resulting lake and the island in its middle are sometimes called the "eye of Quebec."

Vast Expanse

It is believed that when Gosses Bluff crater was originally formed, it measured over 13.5 miles in diameter. After 143 million years, much of it has eroded away, leaving an exposed 3-mile wide formation.

Close Encounter

The Ahnighito Meteorite, at New York's American Museum of Natural History, is one part of a much larger meteorite that fell to Earth (landing in Greenland) thousands of years ago. Even so, at 34 tons, it is the second largest meteorite in the world.

Concentric Rings

Aorounga Crater, in the Sahara Desert, northern Chad, is approximately eight miles wide. It is believed to be several hundred million years old.

Twin Craters

The Clearwater Lakes near Hudson Bay in Quebec were probably formed by a binary asteroid, a system of two asteroids bound to each other by gravity. This photograph was taken from aboard the Challenger space shuttle in 1985.

Man and Crater

Earth experiences from one to three impacts large enough to produce a 12.5-mile diameter crater about once every million years, on average.