Ch.9 Notes

What was the name of the supercontinent ?
Pangaea
What did Wegener argue must have once joined based on fossils ?
Continents
What does rock evidence exists in the form of ?
several mountain belts that end at one coastline
Where were areas of glacial till found ?
Southern Africa,South America,India and Australia
What could Wegener not describe ?
a mechanism that was capable of moving continents across the globe
What is the new theory known as ?
Plate tectonics
What are the segments of the lithosphere called ?
Plates
What is the movement driven by ?
Unequal distribution of heat within earth
What are also called spreading center ?
Divergent boundaries
What happens at convergent boundaries ?
where two plates move together,causing oceanic lithosphere plunging beneath over riding plate and descending into the mantle
What is an example of a transform plate boundary ?
margins where two plates grind each other without the production or destruction of lithosphere
What two things continuously add oceanic lithosphere ?
Fractures and constructive plate margins
What is the longest physical feature on Earth’s surface ?
The system of oceanic ridge
What is the process by which new oceanic lithosphere is produced ?
Seafloor spreading is the process by which plate tectonics produces new oceanic lithosphere
What are subduction zones ?
Destructive plate margins where oceanic crust is being pushed down into the mantle
What two things control convergent boundaries ?
Type of crust involved and the forces acting on the plate
What happens when two oceanic slabs converge ?
one descends beneath the other,this causes volcanic activity
What happens at transform plate boundaries ?
earthquakes occur where there are transformed boundaries.
Where are most transform plate boundaries located ?
Most transform plate boundaries are located within the ocean basins,a few cut through the continental crust
What is normal polarity ?
When rocks show the same magnetism as the present magnetic field
What is the strongest evidence of seafloor spreading ?
The discovery of strips of alternating polarity which lie as mirror images across the ocean ridges
What close link is obvious ?
Scientist found a close link between deep-focus earthquakes and ocean tranches
What was the drilling ship from 1968 to 1983 named ?
Glomar Challenger
What is the basic driving force for plate movement ?
Convection occurring in the mantle is the basic driving force for plate movement