Plate Tectonics Flashcards
What is the continental drift hypothesis?
That the earth’s continents have moved over geologic time
What is evidence for continental drift?,
- Fossils
- Fossil distribution
- Glacial flow Direction
- Rock sequences
What is the plate tectonics theory?
The scientific theory that the outermost layer of the Earth is divided into plates that move relative to one another & that interact at their boundaries
Who is Harry H. Hess?
A geologist & WW2 navy captain who used sonar to discover long mountain ranges on the seafloor
What is sea-floor spreading?
Oceanic lithosphere forms at mid-ocean ridges that gets pushed away from the ridge
What are magnetic polarity stripes?
When earth’s magnetic field reverses, a new stripe, with new polarity, begins
What are Hot spot chains?
A chain of volcanoes formed as a tectonic plate moves over a plume of hot mantle material rising from deep within the earth
What evidence supports plate tectonic theory?
- Mountain ranges on sea-floor
- Symmetry of age of rocks on sea-floor
- Magnetic patterns symmetrical
- Hotspots
What is thermal convection?
The transfer of heat from one place to another due to the movement of fluid
Define ridge push
Magma rises as the plates pull apart, magma cools & forms new oceanic crust, this material slides down away from the ridge, and the plates move apart
Define slab pull
The denser plate will sink back into the mantle and pull the rest of the plate behind it
Define oceanic crust
- The crust beneath ocean basins
- Magic
- Density = 2.9 - 3.0 g/cm3
- Thickness = 5-8km (3-5 miles)
- Oldest = only 180 million years
- Similar composition across the world
Define continental crust
The layer of igneous, sedimentary & metamorphic rocks that forms geological co
What is a convergent boundary?
Plates move towards each other
What is a divergent boundary?
Plates move away from each other
