Chapter 2- Essentials of Geology PLATE TECTONICS Chapter 2- Essentials of Geology
SLO’s for this chapter… I will be able to discuss the view that most geologists held prior to the 1960s regarding the geographic positions of the ocean basins and continents. I will be able to list and explain evidence Wegener presented to support his continental drift hypothesis. I will be able to list the major differences between the Earth’s lithosphere and asthenosphere and explain the importance of each in the plate tectonics theory. I will be able to sketch and describe the movement along a divergent plate boundary that results in the formation of new oceanic lithosphere.
The Continental Puzzle Alfred Wegener German scientist proposed the Continental Drift Continental Drift The continents had once been joined together to form a supercontinent Pangea Broke into smaller continents 200mya The Continental Puzzle
Wegener’s Evidence for Continental Drift Fossil Evidence Several identical fossils found on different landmasses Mesosaurus Reptile Lived in freshwater lake and shallow bays South America & Southern Africa
How does the distribution of Mesosaurus fossils provide evidence for continental drift?
Rock Types Matching rock types Mountain belts that are separated today Appalachians North America to Newfoundland
Ancient Climates Glacial deposits When the ice melts, the mixture of sediment deposits carried by the glacier Proved that ice sheets covered large area of southern hemisphere
What was the evidence that supported the hypothesis of the Continental Drift?
Rejection of Wegener’s Hypothesis Main objection: Wegener could not describe a mechanism capable of moving the continents Tidal influence of the moon
What was Pangea?
https://www.youtube.com/watch?v=zbtAXW-2nz0&t=425s
Why did scientists reject Alfred Wegener’s continental drift hypothesis?
Theory of Plate Tectonics Earth’s lithospheric plates move slowly relative to each other Driven by convection currents in the mantle Theory of Plate Tectonics
Causes of plate motion Convection currents within the earth Magma moves upward by convection Cooler, denser slabs of lithosphere sink into mantle https://www.youtube.com/watch?v=ryrXAGY1dmE&t=3s
Plate motion Averages 1-5cm per year As fast as your fingernails grow Earthquakes, volcanoes, and mountain building
Types of plate boundaries Convergent Form where two plates move together Plates collide Trenches, volcanoes, mountain ranges “destructive” plates
Types of plate boundaries Divergent Found where two plates move apart Spreading centers located along mid- ocean ridges “Constructive” plates Producing new oceanic lithosphere Form Rift Valleys
Types of plate boundaries Transform fault boundaries Occur where two plates grind past each other Does not destroy the lithosphere San Andreas fault Pacific plate moving past N. American plate Earthquake activity