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Mass Extinctions (P-T mass extinction (252ma, Most devastating in Earth…
Mass Extinctions
P-T mass extinction
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Siberian traps- toxic gasses, lava flows and pyroclastic flows killed plants and animals nearby. Ash lowering global temps in atmosphere, causing sea levels to fall, lasted hundreds to thousands of years, greenhouse gasses would have increased temps and increase acid rain
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Methane hydrates- Methane trapped in ice, released when glaciers and ice melted when global temps increased
Launched new recovery of life, and evolution in new forms
Impact event- flimsy and questionable Shocked Quartz crystals found in Australia, very little evidence for this, may have triggered Siberian traps
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Supercontinent formation- Pangea= one large land mass, fewer continental shelves, lack of habitat for shallow marine creatures= accounting for massive decline in marine creatures, would have caused rapid fluctuations in climate and unstable weather patterns
Other theories which are less favourable are- Supercontinent formation and glaciation, Methane hydrates and impact event
Glaciations- widespread glaciation causing sea levels to fall and reducing shallow shelf environments for marine creatures
K - T mass extinction
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Deccan traps India- 30,000 yrs ago effects same as Siberian Traps
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Some groups unaffected- Crocodiles, turtles, lizards, mammals and birds
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Asteroid impact- layer of iridium concentrated in clays originally from space, Shocked Quartz found at boundary, Presence of Tektites (low water content, not formed on earth), Meteor crater found in Yucatan Peninsula in Mexico at Chicxulub (shown by gravity variations and circular depression 180km diameter
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