When you look at our Earth, it doesn't present the same pock-marked surface that our Moon and other planets present, but that's not because these impact craters aren't there. Many of Earth's impact craters have been eroded by weathering processes, while others are either below water or have filled with water.
Bodies that impact our Earth are categorized as follows:
- Asteroid - a large rocky body in space
- Meteoroid - smaller rocks or particles in space
- Meteor - if a meteoroid enters the Earth’s atmosphere and vaporizes, it is called a meteor
- Meteorite - if either an asteroid or meteroid survives its journey through the Earth’s atmosphere and lands, it is called a meteorite
- Bolide - is a very bright meteor that often explodes in the atmosphere.
Scientists identify impact craters by the presence of:
- Shocked quartz - is a form of quartz whose crystalline structure is deformed along planes within the crystal
- Shatter cones - only form in the bedrock beneath meteorite impact craters or underground nuclear explosions, they indicate that the rock has been subjected to pressures of 2 GPa (290,075 psi) to 30 GPa (4,351,132 psi)
- Tektites - are small bodies of natural glass formed from terrestrial debris ejected during meteorite impacts, they can be black, green brown or gray in color.
To find Earth's impact craters, you've just got to know where to look, and we've provided this list to help you find them.
1. Vredefort Crater - South Africa 27°0′S 27°30′E
This crater is not only the largest but also the oldest impact crater on Earth. 2.02 billion years ago, a meteorite or asteroid that was 6.2 to 9.3 miles (10 to 15 km) in diameter crashed and it blasted out a crater 185 miles (300 km) wide.
Vredefort is one of very few multiple-ringed impact craters on Earth. The best-known example is the Valhalla Crater on Callisto, one of Jupiter's moons.
2. Chicxulub Crater - Mexico 21°20′N 89°30′W
In 1978, two geologists working for the Mexican oil company Pemex were conducting an airborne magnetic survey flying over the Yucatán Peninsula. In their data, they noticed an enormous south-facing underwater arc 40 miles (70 km) across.
Consulting an earlier map, they found a matching north-facing arc, and together the two arcs formed a 110 mile (180 km) wide circle centered near the Mexican town of Chicxulub.
At the same time, geologists were examining a white, chalky layer of sediment, called the K-pg boundary, that existed worldwide. Carbon dating showed the layer to be 66 million years old.
A team consisting of the Nobel Prize-winning physicist Luis Alvarez, his son geologist Walter Alvarez, and chemists Frank Asaro and Helen Michel determined that this layer contained an unusual concentration of the element iridium.
Iridium is rarely found in the Earth's crust because it is heavy and it sank into the Earth's core when the planet was molten. Iridium is, however, very plentiful in asteroids, and the Alvarezes suggested that an asteroid must have struck the Earth, and it must have been at least 6.2 miles (10 km) in diameter, or about the size of Manhattan.
For comparison, the Martian moon Phobos is 7 miles (11 km) in diameter, and Mount Everest is just under 5.6 miles (9 km).
Based on the presence of shocked quartz granules in both the K-Pg Layer and around the Caribbean, scientists concluded that the Chicxulub Crater was formed by an asteroid that crashed into Earth 66,038,000 years ago, plus or minus 11,000 years. And, it was this impact that caused the extinction of the dinosaurs.
3. Sudbury Crater - Ontario, Canada 46°36′N 81°11′W
At 1.85 billion years old, Sudbury Crater is exceptionally old. It is currently 81 miles (130 km) wide, but scientists believe it originally measured 160 miles (260 km).
It wasn't until around 1970 that scientists determined that the basin was formed by an impact, due to the presence of shatter cones and shocked quartz. In 2014, scientists determined that the impactor was a comet rather than an asteroid.
Debris from the Sudbury impact has been found as far away as Minnesota, over 500 miles (800 km) away.
4. Popigai Crater - Russia 71°39′N 111°11′E
Around 35 million years ago, a 5-mile-wide (8 km) stony asteroid crashed into carbon-rich graphite rock in Russia's Siberia, creating a 62-mile-wide (100 km) crater.
The immense temperature and pressure caused the humble graphite we know from grammar school pencils to become diamonds. Because of the presence of diamonds, the Popigai Crater was off limits to geologists until 1997.
The Popigai diamonds are small, about 1 mm in size, dark colored, and are used in industrial applications.
5. Manicouagan Crater | Quebec, Canada 51°23′N 68°42′W
What is today a stunning swimming and nature spot was created around 214 million years ago by the impact of a 3-mile-wide (5 km) meteorite resulting in a 60-mile-wide (100 km) multiple-ring crater.
The inner island called René-Levasseur Island, is actually the central peak of the crater, formed by post-impact uplift. Mount Babel is 1,936 feet (590 m) above the reservoir.
Scientists David Rowley of the University of Chicago, John Spray of the University of New Brunswick and Simon Kelley of the Open University have posited that Manicouagan is part of a multiple impact event that also formed the Rochechouart crater in France, Saint Martin crater in Manitoba, Obolon crater in Ukraine, and Red Wing crater in North Dakota.
The five craters appear to form a chain, which indicates the breakup and subsequent impact of an asteroid or comet. This is similar to the string of impacts made on Jupiter by Comet Shoemaker–Levy 9 in 1994.
6. Acraman Crater | Australia 32°1′S 135°27′E
This water-filled crater was created 580 million years ago and is 56 miles (90 km) in diameter. The crater was only identified in 1986 by the presence of shocked quartz and shatter cones on islands in the lake.
Impact ejecta from the crater have been found 185 miles (300 km) away in the Flinders Range, and it contains a high level of iridium, which suggests an extraterrestrial origin.
7. Morokweng Crater | South Africa 26°28′S 23°32′E
Beneath the Kalahari Desert in South Africa's North West province lies the Morokwent Crater. It was formed by an asteroid 145 million years ago and it is approximately 44 miles (70 km) wide.
The crater wasn't discovered until 1994 since it doesn't appear on the surface. In May 2006, a group of scientists discovered fragments of the original asteroid when they drilled to a depth of 2,530 feet (770 m). Some of those fragments are displayed in London's Science Museum.
8. Kara Crater | Russia 69°6′N 64°9′E
At the southeastern end of the Yugorsky Peninsula lies the Kara Crater. Today, it is 40 miles (65 km) in diameter, but is thought to have originally been 75 miles (120 km) in size.
Whatever created the crater crashed into Earth 70 million years ago.
9. Beaverhead Crater | Idaho/Montana, U.S. 44°15′N 114°0′W
At 37 miles (60 km) in width, this crater is one of the largest impact craters on Earth. It spans the border of Idaho and Montana and was created 600 million years ago.
The crater wasn't discovered until the 1990s, when shocked quartz and shatter cones were identified. The center of the crater is the city of Challis, Idaho.
10. Meteor Crater | Arizona, U.S. 35°2′N 111°1′W
37 miles (60 km) east of Flagstaff, Arizona lies Meteor Crater, which is also called Barringer Crater in honor of geologist Daniel Barringer, who first suggested it was created by a meteorite impact.
The crater is 3,900 feet (1,200 m) in diameter and 560 feet (170 m) deep. The impact created a rim that is 148 feet (45 m) above the surrounding area.
The meteorite impacted about 50,000 years ago, during the Pleistocene Epoch, and at that time the area was grassland and wood, and inhabited by mammoths and giant sloths.
The meteorite was nickel-iron and 160 feet (50 m) in diameter. It hit with a speed of around 30,000 mph (12.8 km/s), and about half of the meteorite had been vaporized before impact.
11. Chesapeake Bay Crater | Virginia, U.S. 37°17′N 76°1′W
The Chesapeake Bay off the coasts of Virginia and Delaware is a busy place. It's a population center, and a busy shipping and fishing spot, but look under the mud of the seafloor, and you'll find a crater.
The Chesapeake Bay Crater wasn't discovered until 1983, when a drilling core off Atlantic City, New Jersey turned up tektites and shocked quartz. Then in 1993, teams searching for oil uncovered the extent of the crater.
Formed 35 million years ago during the late Eocene Epoch, the crater is 53-miles-wide (85 km) and .81 mile (1.3 km) deep, making it as deep as the Grand Canyon. The shape of Chesapeake Bay takes its form from the rubble of the crater.
The crater was formed by a bolide, an extremely large impactor that hit at a speed of 60 kilometers per second. This punched a deep hole through the sediment and into the granite forming the continental shelf, fracturing the rock to a depth of 5 miles (8 km).
The impact sent millions of tons of water, sediment and shattered rock into the atmosphere, and a megatsunami rushed inland, possibly as far as the Blue Ridge Mountains.