Ch.9 Survey

What was the name of the super continent?
What did Wegener argue must have once been joined based on fossils?
Erosion continually changes shorelines over time.
What does rock evidence exists in the form of?
They appear as several mountain belts that end at one coastline, only to reappear on a landmass across the ocean
Where were areas of glacial till found?
LAYERS of glacial till were found in southern Africa and South America, as well as India and Australia. It’s interesting that much of the land area that shows evidence of these glaciations now lies near the equator in a subtropical or tropical climate
What could Wegener not describe?
Wegner could not describe a mechanism that was capable of moving the continents across the globe
What is the new theory know as?
The new theory was know as plate tectonics. This theory provides the framework for understanding most geologic process, such as the formation of the mountains?
What are the segments of the lithosphere called?
What is the movement driven by?
The movement is driven by the unequal distribution of heat within Earth.Hot material found deep in the mantle moves slowly upward as part of Earth’s internal convection system.
What are also called spreading centers?
Divergent boundaries
What happens at convergent boundaries?
Two plates move together
What is an example of a transform plate boundary?
Transform plate boundaries are margins where two plates grind past each other without the production or destruction of lithosphere
What two things continuously add oceanic lithosphere?
The system of ocean ridges is the longest physical feature on Earth’s surface
What is the longest physical feature on Earth’s surface?
Seafloor spreading is the process by which plate tectonics produces new oceanic
What is the process by which new oceanic lithosphere is produced?
Destructive plate margins where oceanic crust is being pushed down into the mantle are called subduction zones
What are subduction zones?
The type of crust involved
Forces acting on the plate
What two things control convergent boundaries?
When two oceanic slabs converge, one descends beneath the other.
What happens when two oceanic slabs converge?
At transform plate boundaries, plates grind past each other without destroying the lithosphere
What happens at transform plate boundaries located?
Most transform plate boiundaries 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 percent magnetic field, they show normal polarity
What is the strongest evidence of seafloor spreading?
The discover of stripes of alternating polarity, which lie as mirror images across the ocean ridges, is among the strongest evidence of seafloor spreading
What close link is obvious?
Deep focus earthquakes along the oceanic ridge system was shown to be consistent with the new theory.
What was the drilling ship used from 1968 to 1983 named?
Glomar Challenger
What is the basic driving force for plate movement?
Convection occuring in the mantle