Earth Sciences 2240F/G Study Guide - Winter 2018, Comprehensive Midterm Notes - Carbon Dioxide, Greenhouse Effect, Earth
12 Oct 2018
School
Department
Course
Professor
Earth Sciences
2240F/G
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Phanerozoic Eon- A Trip through time
Introduction:
• Phanerozoic eon: extends from 542 my to today
• Means abundant life, represented by abundant fossil evidence in
rock
• 5 biggest extinction events during this time
• First subdivision of Phanerozoic Eon is the Paleozoic Era
o Includes Cambrian, Ordovician, Silurian, Devonian,
Carboniferous and Permian periods
Cambrian period (542-488 mya)
Plate Tectonics and Life
• Supercontinents Rodinia in latter part of Precambrian, existed
between 1100-750 mya and began to come apart in 750 mya
• New hypothesis that 600-550 mya, fragments came back together
in a different arrangement called Pannolia
o Total disagreement on this
• Rodinia barren continent, life forms in sea, but not on land
• During Cambrian 542-448 mya seas advanced over edges of
fragments, forming numerous shallow and warm bodies of water
were life exploded
• Organisms didn’t simply appear, recent studies show they evolved
very quickly from Precambrian beginnings
• All pre-requisites suddenly available
o Complex multi celled organisms developed at end of
Precambrian and dramatically enlarged suitable habitats with
abundant nutrients in the newly developed shallow warm seas
Cambrian Extinctions
• 2 distinct periods of very strong mass extinction
• each extinction accounts for demise of about 40% of marine genera
• 2 hypotheses advanced: glacial cooling and oxygen depletion
o Glacial Cooling:
▪ Advanced by Miller, states that many of the marine
species developed rapidly in warm water right after
breakup of Rodinia would be completely intolerant of
cold water
▪ Suggest growth of glaciers would have decreased sea
levels and even produced barriers across adjacent
continental shield expanses, thus isolating or
find more resources at oneclass.com
find more resources at oneclass.com
Phanerozoic Eon- A Trip through time
eliminating many of the shallow seas where new species
had developed, giving a second stage to extinction
o Oxygen Depletion
▪ Dependent upon ocean water overturn, bringing anoxic
water to surface
▪ No observation supporting
Profs Preference: glacial cooling + lowering of sea
levels
Ordovician Period (448-444 mya)
Plate Tectonics
• Ordovician period (488-461 mya)
• Southern continents collecting in a single mas, Gondwana
• Earliest Gondwana assembled in equatorial waters, drifted south
until late Ordovician it was centered on south pole and became
covered in continental glaciers
• Assembly accompanied by lots of subduction, so lots of volcanoes
spewing out CO2
• Greenhouse effect strong and marine waters warm
• As shifted south, glaciers built on it, volcanism subsided climate
cooled and ocean waters same temp as today
o This was at early middle Ordovician
• Rest of continent blocks, by middle-late Ordovician, two of biggest
moved towards each other with resultant volcanoes on boundary
• Strong volcanic period, greenhouse strengthened and planet turned
into hothouse
Ordovician Life and Extinctions
• Life flourished
• End of Ordovician marked by series of closely spaced extinctions
that accounted for eliminated of about 50% of marine genera or
about 85% of all species
• Only one larger in Phanerozoic era, is the end Permian
• Survivors were those who could cope with changing conditions
• In 3 my period (447-444 mya) series of sudden and short lived
intense glaciations, thus ending the typical greenhouse conditions
• Thick glaciers sucked up much of the worlds ocean water, bringing
sea levels to dramatic lows
• Shallow water niches eliminated as inland seas disappeared
• As each stage of glaciations ended, and surviving species started to
move into vacated niches, another glacial stage arrived and killed
them off
• Then it was over and sea levels and temperatures normalized
Silurian and Devonian periods
Silurian (444-416 mya)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Precambrian and dramatically enlarged suitable habitats with abundant nutrients in the newly developed shallow warm seas. Phanerozoic eon- a trip through time eliminating many of the shallow seas where new species had developed, giving a second stage to extinction: oxygen depletion, dependent upon ocean water overturn, bringing anoxic water to surface, no observation supporting. Profs preference: glacial cooling + lowering of sea levels. Climate: temperate and few glaciers, mid-devonian sig. cooling, as atmospheric co2 consumed by fast growing forests, by late devonian things had warmed again. Life: the age of fish for enormous biodiversity evoled during this time, the largest and most deadly fish to ever hunt earths seas lived in. Paleozoic era ended and mesozoic era began at 251 mya: mesozoic includes periods triassic, jurassic and cretaceous, ends with another catastrophic event. Climate: dry but quite hot, no glaciations in geological record, even in south pole, polar regions moist and temperate rather than dry and cold.
