Earth Sciences 2240F/G Study Guide - Final Guide: Impact Crater, Cretaceous–Paleogene Extinction Event, Coesite
20 Jan 2018
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Earth science short answers for final: mass extinction, must be global in extent. The time of event must be short <1 million years. Large number of species must become extinct; more than 30% of the total existing at the time. Volcanic eruptions, glaciation, formation of pangaea global climatic cooling, extra-terrestrial impact, or comet showers. Meteorite impact, volcanic eruption, k-t boundary: ke- 1/2mv2, chelyabinsk russia: ke= (1/2) 10000 x 25km/s2= 3,125,000, tunguska russia: ke= (1/2) 4000 x 60km/s2= 7,200,000, tunguska would create the bigger explosion because its kinetic energy is greater. Therefore once transformed into heat with impact, it creates a larger crater: zhamanshin kazakasthan 1 mya, 1 km diameter object caused the impact. Sio2 (coesite phase most common in walls of impact craters)(stisho phase from only pressure impacts), high iridium (tracer of extraterrestrial matter: volcanic crater, the uplift weathering hypothesis: Cenozoic era ending (?) with holocene extinction event today began with k/t extinction event at 65. 5 mya.
