Impact Craters
Impact Craters
 Impact cratering is the dominant geologic process that alters the
solid surfaces of bodies throughout the solar system.
 Impact craters are approximately circular depressions in the surface
of a planet, moon or other solid body in the Solar System, formed by
the hypervelocity impact of a smaller body with the surface.
Barringer “Meteor” Crater, Arizona
Impact Cratering
Impact Craters
 Characteristics
 Rim is raised compared to the surrounding terrain
Impact Craters
Barringer “Meteor” Crater, Arizona
Impact Craters
 Characteristics
 Rim is raised compared to the surrounding terrain
 Floor is lower than the surrounding terrain (Barringer Crater is over 550 ft
deep)
Impact Craters
 Characteristics
 Rim is raised compared to the surrounding terrain
 Floor is lower than the surrounding terrain
 Inverted stratigraphy
Impact Craters
Moenkopi
Kaibab
Coconino
Barringer “Meteor” Crater, Arizona, looking NW
Impact Craters
Moenkopi
Kaibab
Kaibab
Barringer “Meteor” Crater, Arizona, SE rim
Impact Craters
Moenkopi hinge. Barringer “Meteor” Crater, Arizona, NE rim
Impact Craters
Moenkopi hinge. Barringer “Meteor” Crater, Arizona, NE rim
Impact Craters
 Ejecta
Radial ejecta surrounding a lunar crater.
Lobate ejecta surrounding a Martian crater.
Impact Craters
 Characteristics
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Rim is raised compared to the surrounding terrain
Floor is lower than the surrounding terrain
Inverted stratigraphy
Ejecta
Shock metamorphism*
Shatter cones*
Impact Craters
Shock Metamorphism in Coconino Sandstone
Unshocked Coconino Sandstone
Shocked Coconino Sandstone
Images from Traces of Catastrophe by Bevan M. French, 1998
Impact Craters
Shatter Cones
Image Credit: http://www.impact-structures.com/impactrocks-impactites/
From Traces of Catastrophe by Bevan M. French, 1998,
image courtesy of V.L. Sharpton
Impact Craters
 Simple Craters
 Small (relatively) bowl-shaped
depressions with no interior structure
Impact Craters
 Complex Craters & Basins
 Complex craters have interior terraces
and flat floors surrounding central
peaks.
 Basins are craters >300km (~190
miles) in diameter.