EOSC Extinctions.docx

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Department
Earth and Ocean Sciences
Course
EOSC 114
Professor
Leah May Ver
Semester
Spring

Description
EOSC Extinctions 04/21/2014 Mass extinction: effects life across the planet Biosphere: thin layer of life that exits on the surface of the planet (atmosphere, lithosphere an hydrosphere) Principle of Superposition: rock layer at the bottom of the pile will be the oldest etc. Principle of Faunal Successon: age can be recognized by the fossils Biostratigraphy: subdivide geological time using fossils ­ Ussher: calculated the earth to be 6000 year old ­ Eons>Eras>Periods ­ Eons = (Precambrian>Phanerozoic) Eras: broad , grouping of geological periods: major change in the earths biosphere *Precambrian = creatures with soft­bodies = no fossils = not subdividing into periods base of Mesozoic and Cenozoic = emergence of new species following a mass extinction  base = emergence of new species Ga = billions of years ago Ma = millions of years ago MASS EXTINCTIONS: ­ 30% of species lost,  ­ broad range of ecologies ­ short/sudden duration There have been at least 5 major extinctions (the "Big Five") in the Phanerozoic (see figure below): 1. Cretaceous / Paleogene (Tertiary) (K/Pg), 65 Ma 2. Late Triassic, 205 Ma3. Permo / Triassic, 251 Ma4.  Late Devonian, 360­375 Ma 5. Late Ordovician, 440­450 Ma Biologically induced extinction: 1) Competition 2) Excessive predation:  3) Pathogens: Earth Based Causes: 1) Continental configuration = climate, ocean cyclicity, sea level, atmosphere Extraterrestrial impacts, and many factors large landmass = more competition = less diversity 95­98% species extinct: permo­triassic extinction ­ pangea, ice age, volcano, extraterrestrial, climate change , sea level falls LESSON 2:  Cretaceous – Paleogene : (k/pg) 80­90% marine animals extinct ­ Dinosaurs ­ Louis and Walter Alverz: iridum from extraterrestrial stuff, and very rare on earth and also scattered =  10km diameter hitting earth Evidence: ­ferns spread to a
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