3/6/021 Impact features Meteor Crater near Flagstaff, AZ

3/6/022 Instructor has no financial or other interest in Meteor Crater. It’s just a neat place to see.

3/6/023 Characteristics Bowl-shaped raised rim (~100 feet) diameter ~4000 feet depth ~600 feet fragments of an iron meteorite in vicinity (Canyon Diablo meteorite) 25, ,000 years old volcanoes nearby (5 million years old)

3/6/024 Meteor Crater, Arizona

3/6/025 History 1876 Mathias Armijo, cowboy –visited by prospectors, metal fragments –thought to be volcanic 1891 sample of metal sent for analysis –77% iron –2% lead –rest gold and silver

3/6/ A E Foote, a mineralogist, visits –identifies metal fragments as a meteorite –diamonds found in meteorite –crater due to impact 1895 G K Gilbert, Director USGS –not an impact –volcanic 1902 D M Barringer, mining engineer –graduated Princeton at 19 –law school

3/6/027 –studied geology at Harvard –wanted to work in west –discovered Commonwealth silver mine, AZ –rich –visited crater site, was of meteorite origin –bought the place! 1906 published paper outlining his ideas B convinced that a large (several million tons) iron meteorite buried below the crater, worth ~$250,000,000

3/6/028 Barringer’s arguments in favor of impact origin –surrounded by millions of tons of debris pulverized sandstone (Coconino) –oxidized chunks of iron –meteorite fragments mixed with rock debris –overturned rim –no volcanic rocks in crater –no magnetic effect - iron in small pieces

3/6/029 Detailed history and info. –gdcinfo.agg.nrcan.gc.ca:80/crater/ –index_e.html

3/6/0210 Gilbert’s arguments in favor of volcanic origin –no evidence of a large meteorite –no magnetic effect from meteorite –not necessary to have lava in the crater –crater the result of high pressure steam

3/6/0211 Test: A. volcanic - no magnetic effect; volumes equal B. impact - should be a magnetic effect, unequal volumes Gilbert measured and A was correct

3/6/0212 Barringer Drilling in center - nothing decided that the meteorite buried beneath south rim 1919 Gilbert reiterates volcanic theory 1920 B raises more money; drill sticks and breaks - meteorite? 1925 mine shaft - floods, company sinks, B dies

3/6/0213 Geology Couldn’t be simpler (layer cake) horizontal layers of sedimentary rocks each of a different color only three rocks involved –lowest is the Coconino sandstone (white) –middle is the Kaibab limestone (buff) –uppermost is the Moenkopi sandstone (purple)

3/6/0214 Layer-cake arrangement of sedimentary rocks youngest on top excavation rim deformation of the rocks

3/6/0215 New player Eugene Shoemaker PhD from Princeton University doctoral dissertation, Meteor Crater idea that a high velocity object hitting the Earth would be largely vaporized old idea now the ability to simulate with computer

3/6/0216 Mid 1960s

3/6/0217 Estimates Iron meteorite 100 feet in diameter 63,000 tons 15 km/sec energy ~120 megatons of TNT greater than the nuclear device dropped on Hiroshima

3/6/0218 High velocity; example Buffalo - New York is 450 miles =730 km at 15 km/sec, the trip would take 49 seconds meteorites can have velocities of 70 km/sec trip to NY would take 10 seconds And you would be driving a car that weighed 63,000 tons (don’t hit anything!)

3/6/0219 In spite of that - Meteor Crater is a small event.

3/6/0220 Underground nuclear test: Project Sedan

3/6/0221 Overturned rim; reversal of rocks

3/6/0222 Overturned rim: oldest rock on top

3/6/0223 Crater types: bowl shaped, small raised rim Meteor Crater central peak larger terraces Copernicus

3/6/0224 Isidorus, Moon

3/6/0225 Theophilus, Moon

3/6/0226 Gosses Bluff, Australia