Earth Sciences 2240F/G Lecture Notes - Lecture 15: Meteor Crater, Salt Dome, Mineral Collecting
11 Jun 2018
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Chapter 15 Impacts- Case Studies
1.0 Case Study 1: Meteor Crater (Barringer Crater)
• best studied crater on earth
• near present day Flagstaff
• first said to be an explosive hole made by gas-rich volcano, but no
true volcanic rocks were ever found
• then called a weathered out top of a salt dome, but there was no
salt anywhere
• late 1870s
o rumors of chunks of silver found lying on the ground near
Coon Mtn.
• 1891
o sample sent to an assayer in Denver with message that there
was carload of stuff lying around
o assayer was incompetent and reported that the sample was
largely iron, but contained traces of lead, silver and gold
o actually, no lead, silver or gold but 7.9% nickel
o mineral collector recognized the material as probable
meteorite source
o material named for the Canyon Diablo and acknowledged as
being from a meteorite
• not for many years scientists able to declare Canyon Diablo
meteorite was the remnants of the impacter which caused the
crater now called Meteor Crater or Barringer Crater
o Barringer was a geologist who spent most of his life trying to
convince world that this really was an impact crater
o Established the high Ir anomaly characteristic of an
extraterrestrial source
1.1 Crater Geology
• just over 1 km across, almost perfect circle
• hit horizontal sedimentary rocks of the Arizona desert and uplifted
and tilted them away from the explosion creating a rim that rises
45 m
• rim uniform all the way around
• flat floor of crater, which is formed from water-lain sediments of
recent and Pleistocene age lies 185 m below the flat surrounding
desert
• below flat lying sediments, another 265m thickness of shattered
rock (breccia)
• outside crater, little hills composed of the sediments blown out of
the crater, scattered huge blocks of sedimentary rocks (mostly
limestone) and bits of meteorite forming the ejecta blanket
• most of meteorite recovered from crater rim, but some 7 km away
• dust fragments of meteorite recovered in soils as far as 10 km away
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