Download Continental Drift and Plate Tectonics

Continental Drift and Plate Tectonics
Age of Earth estimates through time
Linnaeus
Wallace
Modern radioactive dating
Half life
Oldest fossil
Photoautotrophic prokaryote from
Australia/South Africa (~3.5 bill yrs BP)
Alfred Wegener (1880-1930)
• Proposed the theory of
continental drift in early 1900’s
• Who’s original idea?
• Antonio Snider-Pelligrini (1858)
• Mechanism not explained
Evidence
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Geologic
Stratigraphic
Paleoclimatic
Paleontological
Paleomagnetic
Geologic evidence
Continental slope fit
Geologic evidence
Distribution of earthquakes
Geologic evidence
Distribution of volcanoes
Geologic evidence
Mountain ranges
Stratigraphic evidence
Matching sequence of rock strata on different
continents
Precambrian shields
Flood Basalts
Paleoclimatic evidence
• Glacial deposits
• Scouring on rocks indicate the
direction
Paleoclimatic evidence
Paleontological evidence
Glossopteris fossil record
Paleontological evidence
Mesosaurus fossil record
Paleomagnetic evidence
• Orientation of the
magnetized crystals at the
time of mineral formation
• Earth reverses its
magnetic north at variable
intervals
Paleomagnetic evidence
• Seafloor record of remnant
magnetism (magnetic stripes)
• Every 104 – 106 years
Black - regular,
White – reversed
Computer models – 1965
Marine geology after WWII
• Oceanic floor samples
• Echo soundings
• Oceanic ridges
• Abysall plain
• Denser than continental
• < 150 my old
Continental Drift – continents were once united and have since
become independent structures that have been displaced all
over the globe
Plate Tectonics – study of the origin, movement and destruction
of plates and how these events have been involved in the
evolution of Earth’s crust
Plate tectonics
Crust
Continental (felsic)
Oceanic (mafic)
Mantle
Lower lithosphere
Asthenosphere
Outer Core
Inner Core
Why is continental crust generally much older
than the current oceanic crust?
Plate tectonics
Mid-oceanic ridge
Ridge push
Mantle drag
Slab pull
Plate tectonics
19 major tectonic plates
Plate Boundaries
Divergent boundaries
Convergent boundaries
Transform boundaries
Tectonic history of the continents
Reconstruction of tectonic history
• Paleomagnetic declinations
• Symmetrical magnetic stripes
• Topographic and bathymetric maps
• Lithologic indicators of climate
Tectonic history of the continents
Pangaea: ancient supercontinent (~250 mya)
Tectonic history of the continents
Break up of Pangaea (initiated 180 mya)
• Laurasia rifting
• Landbridges broken
• Gondwanaland
began to separate
Tectonic history of the continents
Most of Gondwanaland separated (100 mya)
Beringia ~75 mya
Tectonic history of the continents
Most of Gondwanaland separated (100 mya)
Landbridges btwn Europe and NA
Tectonic history of the continents
• All continents separated (50 MYA)
• India about to collide with Eurasia (20 cm per year!)
Tectonic history of the continents
Central American Landbridge ~3 mya
Great American Interchange
Formation of Isthmus of Panama – 3
MYA
North American ungulates, proboscids,
carnivorans, rodents dispersed south
South American ground sloths and
terror birds, armadillos dispersed north