Impact craters and meteorites

General description

Category includes outstanding impact craters - detectable scars on the surface of Earth left by a body coming from outer space. Category includes also meteorites - natural objects from the outer space.

Bombardment from the space

Barringer Meteor Crater, United States.
Shane Torgerson, Wikimedia Commons, CC BY 3.0

There are many pieces of solid matter flying around in the space. And VERY frequently they fall on the surface of Earth. There are estimates that every year on Earth fall 18,000 – 84,000 meteorites larger than 10 grams: e.g. one meteorite every 6 – 30 minutes.

The speed of meteorites is dizzying – 15 – 20 kilometres per second! Theoretically they might be even 70 km/s fast (252 000 km/h...). Now try to imagine what happens if meteorite has a diameter of one kilometre and hits the surface of Earth 300 times faster than jet aircraft! It burns a profound hole in atmosphere and kicks the crust of Earth with a terrible force.

Earth has experienced such terrible bombardment. It has been calculated that meteorites with a diameter of 1 km hit Earth every 500,000 years and sometimes there come true behemoths, with a diameter more than 10 km. They leave scars in the surface of Earth and traces in the history of climate and life.

The scars – impact craters

Lonar crater, India.
Nagwani, Wikimedia Commons, CC BY-SA 3.0

As the meteorite hits the ground, it is suddenly stopped by the solid mass of Earth’s crust. Energy can not disappear without a trace – and the immense kinetic energy of the metorite is transformed into thermal energy: an incredible explosion takes place in the impact site. If the meteorite is smaller, it may explode before hitting the Earth surface, but if it is large – it penetrates the ground and explodes under it, creating a circular crater.

The size of such craters on Earth might be amazing. Vredefort Crater in contemporary South Africa was created by 5 – 10 km large asteroid some 2 billion years ago and has a diametre of 250 – 300 km. It seems, this blow triggered creation of new volcanoes around the impact crater. Nowadays it would erase most life forms on Earth.

The giant impact craters have left much more profound changes and can be detected even billions of years later. Such catastrophic events happen very rare – once in ten or hundred million years. As a result these craters still exist but have lost their "visual appeal" – they are just circular structures in the Earth’s crust, very often covered with later sediments.

Smaller impact craters disappear much sooner (if a few million years go together with a term "sooner") but they are more frequent. If they are recent, they still look like true craters and have a visual appeal.

How many impact craters are on Earth?

Aorounga Crater from space.
NASA's Near Earth Object Program, Wikimedia Commons / public domain

The existance of impact craters on Earth has been proved recently – in 1920ies. Since then there have been found some 180 impact craters around the world. They are diverse. Some are small, distinctive and fairly new craters. Some are very old, large and eroded. And – some are covered with sediments and invisible.

Theoretically the density of impact craters on Earth should be uniform – there is no reason to believe that some parts of Earth are hit more often than others.. The density of known craters though isn’t uniform. There are known more craters in:

• Places where the geological exploration has been more intense – United States, Europe, South Africa etc.;
• places, where are exposed old rocks – Canada, Scandinavia, Sahara, Australia.

Very few impact craters are known in oceans – the ocean floor is constantly renewed by geological processes and can not preserve impact craters which are hundreds of millions of years old.

It is expected that many more impact craters will be discovered in the future, but most of them will not be visually impressive structures – they are buried under thick layers of sediments. But there still are discovered visually very interesting impact craters as well – such as the Kamil Crater (Egypt), which was discovered through Google Earth application in 2008.

And, don’t forget, new craters will be formed as well. Every minute there can fall a large meteorite which can cause a devastating explosion and leave a fresh crater.

Outstanding impact craters and meteorites

Below are listed some of the most amazing sand visually most interesting impact craters known on Earth, arranged by the part of the world and in an alphabetic order:

Africa

Hoba meteorite, Namibia.
Damien du Toit, Flickr, CC BY 2.0.

• Amguid crater - Algeria, Tamanrasset. Very well pronounced impact crater, less than 100,000 years old. Diametre – 550 m, 65 m deep.
• Aorounga crater – Chad, Borkou. Remnant of eroded impact crater with a diametre 12.6 km. Formed 345 million years ago or more recently. Looks impressive on satellite images.
• Aouelloul crater - Mauritania, Adrar. Well preserved impact crater. Formed approximately 3 million years ago (Pliocene). Diametre 390 m.
• BP Crater - Libya, Al Kufrah. Old, eroded but nevertheless visible impact crater. Diameter – 2 km, less than 120 million years old.
• Dar al Gani meteorite field - Libya, Al Jufrah. A desert plateau – a famous site where more than 1200 meteorites have been found with total mass over 690 kg. Meteorites here have accrued over the time – here have accrued meteorites of different time periods.
• Hoba meteorite – Namibia, Otjozondjupa. The largest known single-piece meteorite and the largest known natural piece of iron on Earth. The stone fell some 80,000 years ago, it weighs more than 60 tons, 2.7 by 2.7 m long.
• Lake Bosumtwi - Ghana, Ashanti. Ancient meteorite impact crater, 10.5 km across, formed 1.07 million years ago. Filled with 8 km wide lake – the only natural lake in Ghana. Surrounded by a dense rainforest.
• Kalkkop crater - South Africa, East Cape. Some 250,000 years old impact crater. Diametre – 640 metres. Crater now is filled with light limestone deposits and is visible as a white circle.
• Kamil Crater - Egypt, New Valley Governorate. Well preserved, approximately 5,000 years old impact crater. Width is 44.8 m, depth – some 12 – 13 m. Around the crater still visible the rayed structure created by the blast.
• Roter Kamm crater – Namibia, Karas. Approximately 3.7 million years old impact crater. Diameter of the crater is 2.5 km, depth – 100 m. It was deeper earlier – the bottom is covered with 100 m thick layer of sand.
• Tenoumer crater - Mauritania, Tiris Zemmour. Well visible, interesting impact crater. Diametre – 1.9 km, depth 110 m, age – approximately 21,400 years.
• Tswaing crater - South Africa, Gauteng. Approximately 220,000 years old impact crater, 1.13 km in diameter, up to 100 m deep. At the bottom of the crater is a salt lake. People have visited this crater over the last 100,000 years.
• Vredefort Crater - South Africa, Free State Province. The largest verified impact crater on Earth. This 250 – 300 m wide impact crater was created 2 billion years ago by a bolide 5 – 10 km in diameter.

Asia

Fallen trees in the site of Tunguska event in 1929, Russia.
Expedition of Leonid Kulik, Wikimedia Commons, public domain.

• Elgygytgyn Lake – Russia, Chukotka Autonomous Okrug. Impact crater, filled with a lake. The lake is approximately 15 km in diameter, with a maximum depth of 175 m. Diameter of the crater is 18 km. Formed in Pliocene, 3.6 million years ago. The lake has never been covered with glaciers.
• Lonar crater – India, Maharashtra. A meteorite crater filled with saltwater lake. The bolide hit the basalitc rock some 52,000 years ago. The diameter of the crater is 1.8 km, with 1.2 km wide lake in it, depth – circa 150 m.
• Popigai Crater – Russia, Krasnoyarsk Krai. Giant impact crater with a diametre of 100 km. Created approximately 35.7 million years ago (Eocene) by a 5 – 8 km large bolide. Here are found up to 1 cm large diamonds created by the impact.
• Sikhote-Alin meteorite strewn field - Russia, Primorsky Krai. A 1.3 km² large area, where in 1947 fell a meteorite shower with joint mass of 70 tons. The largest crater was 26 m across and 5 m deep.
• Tunguska event epicentre – Russia, Krasnoyarsk Krai. The site where an enormous explosion took place in June 30 1908. It is considered that this blast was caused by large meteoroid and is the largest impact in land in the newest history of Earth. Similar event in metropolitan area would lead to death of millions of people.
• Wabar craters (al-Hadida meteors) – Saudi Arabia, Ash Sharqiyah, Unusual impact craters in the desert of Arabia. Legendary site, where iron meteorites of large size reportedly have been found. Well preserved craters show that the impact was very recent.

Australia and Oceania

Wolfe Creek Crater, Australia.
user Kookaburra, Wikimedia Commons, public domain.

• Boxhole crater – Australia, Northern Territory. Well visible impact crater, with a diametre of 170 m. Formed some 5,400 m years ago.
• Henbury meteorite craters – Australia, Northern Territory. A group of 13 – 14 meteorite craters with a diametre from 7 to 180 m, up to 15 m deep. Here have been found several tonnes of meteorites. Formed some 4,200 years ago.
• Mahuika Crater – New Zealand, near Snares Islands. Potential impact crater on the bottom of sea, 20 km wide and more than 153 m deep. It is possible, that the meteorite fell circa 1443 AD, creating incredible tsunami waves up to 220 m high.
• Veevers crater – Australia, Western Australia. One of the best preserved small impact craters, formed some 4000 years ago or later. Diametre – 70 m, depth – 7 m. The rim is 1.5 m high.
• Wolfe Creek Crater – Australia, Western Australia. Very well preserved impact crater, formed less than 300,000 years ago. Diametre – 875 m, depth – 60 m.

Kaali crater, Estonia.
Siim Ainsaar, Wikimedia Commons, CC BY-SA 3.0.

Europe

• Kaali crater - Estonia, Saaremaa. Fairly recent (4000 – 2700 years old), well preserved meteorite craters. The largest crater has a diametre of 110 m and 22 m depth. It has a lake at its bottm and exposed limestone along its rim. The fall of meteorite created legends.
• Nördlinger Ries – Germany, Bavaria. Enormous impact crater – a large circular depression with a diameter of 24 km. Formed 14.3 – 14.5 million years ago (Miocene). Currently the crater is 100 – 150 m deep, at some places there are exposed the rims.

North America

Pingualuit crater, Canada.
user Lkovac, Wikimedia Commons, CC BY-SA 3.0.

• Barringer Meteor Crater – United States, Arizona. Visually the most impressive meteorite impact crater on Earth. Diameter of the crater is about 1,200 m, depth – 170 m. The outer side of the rim rises 45 m high above the surrounding plains. The bottom is covered with 210 – 240 m thick layer of rubble. Impact took place some 50,000 years ago.
• Clearwater Lakes – Canada, Quebec. A pair of large meteorite craters –two connected lakes. Diameter of lakes – 26 and 36 km, both created in Permian (290 million years ago). The larger lake has a ring-shaped circle of islands in the centre.
• Chicxulub crater – Mexico, Yucatán. Ancient impact crater, with a diameter more than 180 km. One of the largest impact craters on Earth. It was shaped 65 million years ago and it is considered that this fall of bolide led to the great extinction of dinosaurs and many other animals and plants.
• Haughton impact crater – Canada, Nunavut. This impact crater is located in very remote area on Devon Island. Diameter – 23 km, formed some 39 million years ago (Eocene). Permafrost has helped to preserve this impact crater very well and the site is considered to have a very similar environment to Mars.
• Manicouagan Reservoir – Canada, Quebec. Enormous, ring-shaped reservoir, formed in impact crater. The impact took place 214 million years ago, shaping approximately 100 km wide crater. The central part of the lake is taken by the enormous René-Levasseur Island, with 2,020 km² area.
• Pingualuit crater (Chubb Crater) – Canada, Quebec. Well pronounced and well preserved impact crater, 3.44 km in diameter. Formed circa 1.4 million years ago, in Pleistocene. Rims of the crater rise 160 m above the tundra. Depth of crater is 400 m, it is partly filled with 252 m deep Pingaluit lake. Lake water is one of the purest in the world, second most transparent lake in the world.
• Upheaval Dome – United States, Utah. Deeply eroded but nevertheless well visible impact crater. Diameter – 5 km, age – less than 170 million years (Jurasssic). Now here are well seen the eroded central dome of the structure.

South America

Monturaqui Crater.
Rudolf Reiser, Wikimedia Commons / CC BY-SA 3.0

• Carancas impact site – Peru, Puno. Site, where in September 2007 fell a meteorite. It created 4.5 m deep crater, 13 m wide. More than 600 local people later became ill, the nature of this illness is not explained.
• Campo del Cielo – Argentina, Chaco and Santiago del Estero. A strewn field of iron meteorites, which fell some 4 – 5 thousand years ago. The largest meteorite fragment weighs 37 tonnes and is the second heaviest after Hoba meteorite, total weight of meteorites – more than 60 tonnes. 26 impact craters, the largest is 115 by 91 m large.
• Monturaqui Crater – Chile, Antofagasta. Well pronounced meteorite crater, 350 – 370 m in diameter and less than 1 million years old.
• Vargeão Dome – Brazil, Santa Catarina. Less than 70 million years old impact crater – a circular depression with steep walls. Diametre – 12 km, up to 225 m deep.