Impact Crater Images
An impact crater forms when an asteroid or comet strikes
another body such as an asteroid, planet, or moon at high speed. All of the
surfaces of the inner planets and their moons (Mercury, Venus, Earth, and Mars)
have been heavily bombarded. Because the Earth is so active geologically,
most traces of impact craters have been erased by erosion and
tectonic activity. Nevertheless, over one hundred seventy impact craters have been
identified on Earth. Several more are found each year.
The impacting body generally melts and mixes with the rocks at the impact site.
Sometimes the impact site reveals an abundance of siderophile elements
such as iridium, osmium, platinum, and palladium.
Other tell-tale signs of an impact are products of shock metamorphism
such as shatter cones, planar features in quartz
and feldspar, diaplectic glass, and a high-pressure form of quartz called
stishovite. Stishovite has never been found anywhere else but
Impact craters may be simple or complex.
Simple craters are relatively small with a smooth bowl shape, and
exhibit a depth-to-diameter ratio of about one-to-six.
Meteor Crater in Arizona is a good example of a simple impact crater.
This crater is about 1,200 meters in diameter and 170 meters deep.
The crater rim rises nearly 80 meters about the surrounding plain.
The crater was formed between 20,000 and 50,000 years ago by the impact of an
iron meteorite weighing over over 60,000 tons.
The photograph of Meteor Crater at the top of this page was taken by
David Roddy of the United States Geological Survey.
Complex craters are larger in diameter but shallower in depth.
Complex craters usually possess a depth-to-diameter ratio of
between one-to-ten and one-to-twenty. Gravity collapses the crater
walls downward and inward. A central peak may form when the
crater floor rebounds from the impact. To become complex, a crater
must have a large enough diameter. On Earth the transition diameter
lies between two and four kilometers.
I actually live within the boundaries of an ancient buried impact
structure located in Des Plaines, Illinois, USA. This eight kilometer
diameter crater is about 280 million years old.
There is no surface evidence for the crater which lies buried under
glacial drift. However, the roughly circular
site exhibits complex faulting and shock features such as
percussion fractures and strain lamellae, as well as a few
The center of the crater lies under Big Bend Lake on the
Des Plaines River.
A good source of information and images for terrestrial impact craters
is Paul Hodge's book
Meteorite craters and impact structures of the Earth.
Hodge describes 139 impact sites around the world.
- Aorounga impact crater, Chad
offers an SIR-C/X image of this crater which some scientists
suggest is part of a string of impact craters formed by multiple
impacts. Interestingly, estimates of the date of the impact which
formed this crater vary widely. French geologists who examined the
crater on the ground suggest a Holocene date -- possible as young as
4,000 years ago -- while NASA suggests a date about 360 million
years ago. The most recent estimated date is about 800,000
- Crater Chains on the Earth and Moon
by Bill Bottke discusses crater chains on the Earth and the Moon.
Includes photos of the Aorounga, Chad site and several lunar
- Earth Impact Database
from the Planetary and Space Science Center of the University of
New Brunswick provides a list of the known impact sites on Earth.
For each, the name, location (country, latitude, longitude),
estimated age, diameter, and exposure are provided. Photos are also
included for most impact locations. Includes an excellent
introduction to impact processes, morphology, impact site
identification, and impact hazards, along with a short bibliography.
Available in both French and English.
of terrestrial impact craters from NASA's NEO project include
Meteor Crater, Arizona; Chicxulub, Yucatan, Mexico; Aorounga, Chad;
Manacougan, Canada, and Roter Kamm, Namibia.
- Impact crater list
by Jarmo Moilanen offers an up-to-date list of proved and
suspected impact craters along with links to web pages with more
information about each.
- Impact Craters Activity
by the Hawaii Space Grant Consortium offers a teaching guide for a
"hands-on" activity to determine factors affecting the appearance of
impact craters and ejecta.
- Impact Sites
by Steven Dutch offers a map and list of impact crater sites.
- Ernston-Claudin Impact Structures
by Kord Ernstson and Fernando Claudin offers a database of
terrestrial impact structures as well as information about
impacttites, impact ejecta, shock metamorphism, the geophysics of
impact structures, and a bibliography.
- Meteor Crater Enterprises, Inc.
provides the history of the famous Barringer meteor crater in
Arizona, USA. This crater is about 4,000 feet (1,200 meters) wide
and about 550 feet (170 meters) deep.
- Meteor Crater in 3D
offers two images which can be combined by crossing your eyes into
a three dimensional photo of the Barringer meteor crater in Arizona,
- Strange Craters Formed by Oblique Impacts
by Bill Bottke offers images of craters formed by oblique impacts
on Venus, Mars, and Earth's moon.
- Terrestrial Impact Crater List
lists a number of impact craters and includes a panoramic Quicktime
movie view of Meteor Crater, Arizona as well as an MPEG movie of a
simulation of an impact event.
- Terrestrial Impact Craters
compiled by Calvin J. Hamilton clearly show that the Earth, like
the Moon and other terrestrial planets, bears scars caused by the
impact of extraterrestrial objects.
- Terrestrial Impact Craters Slide Set
compiled by Christian Koeberl and Virgil L. Sharpton offers images
of forty impact sites around the world.
- Tswaing/Soutpan Meteor Crater
is located forty kilometers north of Pretoria, South Africa. The
crater, which is about a kilometer in diameter, was formed by an
impact about 200,000 years ago.
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Last modified by
pib on May 12, 2009.