the dynamic earth and plate tectonics
DESCRIPTION
the Dynamic Earth and Plate Tectonics . Early Ideas on a moving Earth. Alfred Wegener proposed idea: “ Continental Drift ” Stated that all continents used to be joined in Pangaea (meaning “all land”) that broke up into smaller continents, “drifted” to current locations - PowerPoint PPT PresentationTRANSCRIPT
the Dynamic Earth and Plate Tectonics
Early Ideas on a moving Earth• Alfred Wegener proposed idea: “Continental
Drift”– Stated that all continents used to be joined in
Pangaea (meaning “all land”) that broke up into smaller continents, “drifted” to current locations
What patterns do we see in continent shapes?
Continental Drift - Wegener’s hypothesis of continent movement after Pangaea broke apart
Early evidence #1:Coastlines on early maps seem to fit like puzzle pieces
Why are there fossils of cynognathus on both Africa and South America and no where else?
“Continental Drift”, Early evidence #2
Fossils of the same organism were on opposite land masses (puzzle pieces), known to have been joined at one time
Why do rocks from Rhode Island and Scotland match?
“Continental Drift”, early evidence #3
Mountains and rocks continued on opposite puzzle pieces
Why did southern India used to have glaciers?
“Continental Drift”, early evidence #4
Misplaced glacial remnants
and tropical swamps can be
explained if continents were
once joined
Newer evidence• Proof of seafloor spreading at the Mid-
Atlantic Ridge (1947)– Rock at the ridge was dated much younger than
continental rock– Paleomagnetism also apparent • As magma solidifies, iron crystals align with
Earth’s magnetic field like a compass. Geologists have known that this happens periodically throughout history, as magnetic poles flip flop.
Modern Theory of Plate Tectonics
• Earth is made up of 9 primary plates and several microplates made up of continental and oceanic crust.– Upper lithosphere is crusty and moves about on
plasticy asthenosphere.– Asthenosphere moves most likely due to convection in
the mantle due to heat from core and radioactivity from mantle
• Where plates meet is called a plate boundary– Types: Convergent, divergent, transform
PLATE BOUNDARIES1. Convergent Boundary• Ocean – Continent• Ocean – Ocean• Continent – Continent
Continent – Continent convergence
Ocean – Continent Convergence
2. Divergent Boundary
3. Transform Boundary
Where in the World do we find those
boundaries?