Today – 1/19 Administrative details Prepare for workshop Radiometric dating

Admistrative details Book OH: Mon 12:30-1:30, Tues 10:30-11:30 Hmwk 1 Tests XC

Titan from Huygens

Cassini extra credit opportunity Saturday 6:15-7:45 pm 5 points Sit with me, or Check-in with me, 1-page summary Times New Roman 12 point font Double-spaced Hand copy 1 image on separate page

The Three Rock Types Igneous – crystallize (freeze) from liquid Metamorphic – pre-existing rocks are altered by pressure/temperature Sedimentary – accumulations of fragments of pre-existing rocks lithify OR minerals precipitate from aqueous solution

In this class: Strata = layers of sedimentary rocks FYI – bed / formation / group / section / unit: groupings of strata Stratigraphy: study of strata Stratigraphic column: graphic representation of strata

Arizona

Arizona

More Geospeak: Lower = early = older Upper = late = younger MYa = Ma = million years ago/old GYa = Ga = billion years ago/old

Workshop 1 Significant Events in Earth History Significant Events in Earth History In parentheses are the pages from the text that will help you complete this exercise. Two examples are completed. In parentheses are the pages from the text that will help you complete this exercise. Two examples are completed. Dinosaurs go extinct (pp & ) Dinosaurs go extinct (pp & ) Earliest evidence of life – oldest known fossils (pp ) Earliest evidence of life – oldest known fossils (pp ) Oldest rock – earliest evidence for stable crust (lecture notes) Oldest rock – earliest evidence for stable crust (lecture notes) Cambrian expansion of life (pp ) Cambrian expansion of life (pp ) Humans evolve (lecture notes) Humans evolve (lecture notes) Moon forms (pp & lecture notes) Moon forms (pp & lecture notes) Earliest evidence for animals on land (pp ) Earliest evidence for animals on land (pp ) End of heavy bombardment of the Earth (pp ) End of heavy bombardment of the Earth (pp ) Oxygen builds up in atmosphere (pp & ) Oxygen builds up in atmosphere (pp & ) First land plants appear (pp and lecture notes) First land plants appear (pp and lecture notes) Dinosaurs (reptiles) rule the Earth Dinosaurs (reptiles) rule the Earth Last glaciation (major global advance of ice) culminates (pp ) Last glaciation (major global advance of ice) culminates (pp ) Cenozoic _____________________________ Dinosaurs go extinct_____________ Mesozoic Dinos rule the Earth Paleozoic _____________________________ Precambrian (Proterozoic/Archean/Hadean) _____________________________ Earth forms (4.5 Ga) Right now (0 Ga) Dates

Radiometric Dating Absolute versus relative Elements defined by #protons Isotopes of an element = different #neutrons Some isotopes unstable, decay

Age of the Earth Problem: no rocks exist to date Solution: meteorites! Formed fast! 4.54 Ga

Period of Heavy Bombardment Ga Earth’s ancient surface gone, so how do we know? Computer models + can see the crater evidence of this period on other bodies like the Moon and Mars

Formation of the Moon Theories: fission, capture, condensation Problems: low density, no volatiles, oxygen isotopic signature same as Earth Solution: biggest bomb of them all!

Moon formation picture

Giant Impact Simulation

Moon Oldest rock ~4.4 Ga When did the big bomb hit? Formed in less than a year 14,000 miles away (238,000 now)

Evolution of Man Earliest fossils after divergence from chimps ~5 Ma Fully modern by 50 Ka