In This Chapter: Composition of the Earth Layers of the Earth:
crust, outer core, inner core, mantle Continental Drift Theory
Evidence: fossil clues, climate clues, rock clues Pangaea Theory of
Seafloor Spreading Evidence: rock and magnetic clues Plate
Tectonics Plate movements Plate boundaries Convection currents
Slide 3
Fossil Rock Anthem
http://www.youtube.com/watch?v=ClJ5lwl_wM0
Slide 4
Continental Drift Theory Proposed by Alfred Wegner Continents
were at one time all joined together (Pangaea)
Clues to Pangaea Climate Clues Fossils of warm water plants
found on Arctic Ocean island (Glossopteris) Glacial deposits &
grooved bedrock in South America, Africa, India, and Australia
These areas were once connected
http://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Pangaea_Glossopteris.jpg/220p
x-Pangaea_Glossopteris.jpg
Slide 8
Clues to Pangaea Rock Clues Similar rock structures are found
on different continents Ex. Appalachian Mountains: Eastern U.S.
Greenland Western Europe
http://www.jamestown-ri.info/Pangaea_mts.jpg
Slide 9
How Do The Continents Drift? Theory of Seafloor Spreading
supports Wegeners theory
http://mail.colonial.net/~hkaiter/Aaa_web_images2012/sfsseafloor_spreading.gif
Slide 10
Theory of Seafloor Spreading Proposed by Harry Hess in 1960s
Hot, less dense material in mantle is forced upward to surface at
Mid Ocean Ridge It cools, contracts, turns, and flows sideways,
carrying the seafloor away from the ridge in both directions MAGMA!
Moves upward, flows into cracks, solidifies to form new
seafloor
Slide 11
Evidence of Seafloor Spreading Age difference in rocks Glomar
Challenger (research ship) found youngest rocks are near center of
ridges Magnetic clues Magnetic field has reversed itself
http://www.gcsescience.com/Magnetic-Reversal-Mid-Ocean-Ridge.gif
Slide 12
Plate Tectonics Plate movements The Earths crust and upper
mantle are broken into sections called plates
http://www.enchantedlearning.com/egifs/Earthsplates.GIF
Slide 13
Earths Composition Lithosphere Upper mantle and crust Rigid,
less dense than material below it; divided into plates Floats on
asthenosphere Asthenosphere Located below lithosphere More dense,
plastic-like
Plate Boundaries Divergent Boundary (divide) Plates move away
from each other
http://geographicalconcepts.wikispaces.com/file/view/db.jpg/177810579/db.jpg
Slide 16
Plate Boundaries Convergent Boundary One fault surface is
forced up and over the other fault surface Forms mountains &
subduction zones
http://www.geo.cornell.edu/hawaii/220/PRI/images/subduction2.jpg
Slide 17
Plate Boundaries Transform Boundary Plates slide past each
other Not much upward/downward movement
http://www.divediscover.whoi.edu/images/tectonics-slide.jpg
Slide 18
Causes of Plate Tectonics
http://rockdale.k12.ga.us/schools/dms/class/jtamburro/Class%20Documents/Geology%20Unit/Convection%20current.JPG
Slide 19
Effects of Plate Tectonics Volcanoes Earthquakes Mountain
building Ocean rift formation Tsunamis Ocean basins
Slide 20
Review What are the 3 types of clues for Pangaea? Who proposed
the Continental Drift Theory? What theory did Harry Hess propose?
What is the difference between the lithosphere and
asthenosphere?