age of the earth. subdivisions of geologic time –eon, era, period, epoch –eons precambrian: 4.5...
TRANSCRIPT
Age of the EarthAge of the Earth
• Subdivisions of geologic time– Eon, Era, Period, Epoch
– Eons• Precambrian: 4.5 b.y. to ~0.5 b.y.
• Phanerozoic: ~0.5 b.y. to today
Geologic time scaleGeologic time scale
• Subdivisions of geologic time– Eon, Era, Period, Epoch
– Eras• Paleozoic: ~560 m.y. to ~250 m.y.
• Mesozoic: ~250 m.y. to ~65 m.y.
• Cenozoic: ~65 m.y. to today
Geologic time scaleGeologic time scale
Image source: http://www.gly.fsu.edu/~salters/GLY1000/12Rock_record_time/Slide27.jpg
Plate Tectonics- OverviewPlate Tectonics- Overview
• Plate Tectonics–General Principles
• Plate Movements–Accumulating Evidence
• Types of Plate Boundaries
• How Far, How Fast, How Long, How Come?
• Plate Tectonics and the Rock Cycle
Plate Tectonics–General Plate Tectonics–General PrinciplesPrinciples
• Stress and Strain in Geologic Materials
• Lithosphere and Asthenosphere
• Locating Plate Boundaries
TectonicsTectonics
• Stress- application of a force– Compressive (pushing together)– Tensile (pulling apart)
• Strain- deformation response of the force– Elastic deformation: ‘rubber band’– Plastic deformation: permanent strain– Rupture: the breaking point
Folding Rock
Source: Photograph courtesy of M.R. Mudge; courtesy USGS Photo Library, Denver, CO.
Folding and Faulting, Cook Inlet, Alaska
Source: Photograph by N.J. Silberling, USGS Photo Library, Denver, CO.
Rock Failure Under Stress
Source: Photograph courtesy of W.B. Hamilton; courtesy USGS Photo Library, Denver, CO.
Effect of tectonics on rocksEffect of tectonics on rocks
• Depends of physical conditions– Temperature & pressure
– composition, time, fluids
Lithosphere- AsthenosphereLithosphere- Asthenosphere
Lithosphere-AsthenosphereLithosphere-Asthenosphere
• Lithosphere (lithos = rock)– Brittle, elastic outer layer
– ~50 km under oceans, ~100 km under continents
• Asthenosphere (asthenes= without strength)– Plastic domain
– ~300 km in mantle
– Discovered by seismic wave studies
Plate boundariesPlate boundaries
• Deformation, earthquakes, and volcanoes are not evenly distributed around the Earth
• Mostly concentrated in linear belts, chains• Can use distribution to ‘map out’ plates• ~8 major plates, several smaller ones
World Locations of Volcanoes and Earthquakes
Source: Map plotted by the Environmental Data and Information Service of NOAA; earthquakes from U.S. Coast and Geodetic Survey.
Plate Movements–Accumulating Plate Movements–Accumulating EvidenceEvidence
• The Topography of the Sea Floor
• Magnetism in Rocks–General
• Paleomagnetism and Seafloor Spreading
• Age of the Ocean Floor
• Polar-Wander Curves
• Other Evidence
Shaded Relief Map of the World
Source: Photo courtesy of NOAA National Geophysical Data Center.
Shaded Relief Map of the World
Source: Photo courtesy of NOAA National Geophysical Data Center.
The Earth is a large bar magnet…
And sometime it flips…!
(1) Minerals oriented randomly in a melt
(2) Minerals aligned in the magnetic field
Minerals: the ‘Curie Temperature’
First magnetic survey of the oceans
Age Distribution of the Sea Floor
Source: Marine Geology and Geophysics Division of the NOAA National Geophysical Data Center.
World Locations of Volcanoes and Earthquakes
Source: Map plotted by the Environmental Data and Information Service of NOAA; earthquakes from U.S. Coast and Geodetic Survey.
World Lithospheric Plates
Source: After W. Hamilton, U.S. Geological Survey.
Source: http://www.mq.edu.au/scienceresearch/lackie.htm
Polar Wander
Plate Movements — Today
Source: After R.S. Dietz and J.C. Holden, “Reconstruction of Pangaea,” Journal of Geophysical Research, 75:4939-4956, 1970, copyright by the American Geophysical Union.
Plate Movements — 100 Million Years Ago
Source: After R.S. Dietz and J.C. Holden, “Reconstruction of Pangaea,” Journal of Geophysical Research, 75:4939-4956, 1970, copyright by the American Geophysical Union.
Plate Movements— 200 Million Years Ago
Source: After R.S. Dietz and J.C. Holden, “Reconstruction of Pangaea,” Journal of Geophysical Research, 75:4939-4956, 1970, copyright by the American Geophysical Union.
Glacial Deposits Across Southern Continents
Source: After Arthur Holmes, Principles of Physical Geology, 2d ed., Ronald Press, New York, NY, 1965.
Types of Plate BoundariesTypes of Plate Boundaries
• Divergent Plate Boundaries– Rifts, Mid ocean ridges, lots of volcanism
• Transform Boundaries– Sliding plates, lots of earthquakes
• Convergent Plate Boundaries– Subduction zones, mountain belts
Divergent plate boundary: East African Rift
Satellite Image of Lake Tanganyika, Africa
Source: © NASA
Transform plate boundary: San Andreas strike-slip fault
Convergent plate boundary: Subduction Zone in Alaska
Source: Image courtesy of NOAA National Geophysical Data Center.
Convergent plate boundary: Where are we?
Current Motions of Major Plates: Satellite laser data
Source: Data from NASA.