1. BEFORE PANGAEA
EPSC 510 // PRESENTATION 1

2. CURRENT THEORY
Plate tectonics -- Earth’s continental and oceanic crusts divided into plates
Convection from inner Earth causes movement of plates//tectonic activity
Earthquakes, mountain ranges, volcanic activity, ocean trenches, etc.
Outcome: the geological landscape we know today

3. History
Alfred Wagner theory of continental drift -- later developed into theory of plate tectonics
Supercontinent Rodinia (~1 Ga) fragmented into smaller continents, then reassembled into…
Supercontinent Pangaea (~ Ma) fragmented into two smaller continents…
Laurasia and Gondwana (~200 Ma) fragmented into…
Current layout of continents on Earth

4. Proof Shapes of continents -- jig-saw puzzle
Fossil comparison -- species similarity at distant continental boundaries
Geo-sequences -- similar deposits at distant boundaries
Paleomagnetism -- polar wandering paths
Position of plate boundaries -- location of major seismic, volcanic, geothermal activity
Mid-Ocean Ridges -- clear indicators of mantle convection (driving force of tectonics)
Quantitative measurements of plate movement -- a few cm/yr

5. But where did the tectonic plates come from?
Theory of plate tectonics implies a dynamic Earth through time -- future, present and past
Why do we assume supercontinents were the beginning? Did they just appear out of thin air?

6. Cratons
Cratons -- building blocks of continents, often found in interior of tectonic plates
Very old stable basement rock which roots deep into the lithosphere -- older than oceanic lithosphere
These cratons supposedly formed during the Archean
At this time, the Earth was much hotter -- greater heat flow, less viscous mantle -- high turnover of oceanic crust
Continental evolution -- many steps before Pangaea
“The Early Earth and Plate Tectonics” --