Continental Drift

Continental Drift

Theory First person to think the continents fit together – mapmaker, Abraham Ortelius First to propose the idea of Continental Drift was meteorologist – Alfred Wegener – Hypothesis that continents were connected but broke apart 200 million years ago and drifted to current position

Pangaea Wegener suggested the continents were once connected as one large landmass called Pangaea

The Earth appears to be cracked into pieces called plate tectonics. (Like a cracked egg shell) 5. Some plates move in opposite directions (Divergent). Some plates collide (Convergent) Some plates slide past each other (transform boundary)

Divergent Boundaries Two plates that are moving apart. This is seafloor spreading Hot material rises to create new lithosphere Volcanoes and earthquakes common Rift valley – the crack Deep-sea trenches Ex: Mid-Atlantic Ridge

Convergent Plate Boundaries Two plates move together A: Continental plate vs. continental plate – Same densities, neither sinks below the other causing folded mtns. – Earthquakes common – EX: Appalachian Mtns., Himalayan Mtns., Alps

Continental plate vs. oceanic plate – Oceanic plate is more dense so sinks or subducts under continental plate – SUBDUCTION ZONE: WHERE ONE PLATE SINKS BELOW ANOTHER – High temps melt the subducting rock – Volcanoes and earthquakes common – EX: Cascade Mtns. in Washington, Andes Mtns.

Transform Plate Boundaries Where two plates slide past one another – Can move opposite directions – Same direction at different speeds – Earthquakes common