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Chapter 8 Study Guide. 1) Who is Alfred Wegener and what did he contribute to science?. 1) . Wegener was a geologist in the 1900’s who questions the thought of the continents being in a fixed position. Wegener formed a hypothesis that the continents had moved!!
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1) Who is Alfred Wegener and what did he contribute to science?
1) • Wegener was a geologist in the 1900’s who questions the thought of the continents being in a fixed position. • Wegener formed a hypothesis that the continents had moved!! • His hypothesis stated that the continents were once a single landmass that have now been separated! • He named this giant landmass Pangaea, meaning “all lands”.
2) What were Wegener’s three pieces of evidence and how did they prove his theory of Continental drift?
2) • Landform Evidence • Wegener noticed that Large mountain ranges on different continents would match up if pieced together. • He also noticed that Coal fields on different continents would match up and have the same type of coal.
2) • Fossil Evidence • Wegener noticed that fossils such as the Mesosaurus were on two different continents ( South America, Africa) This was a reptile that could not swim great distances in salt water. What does this tell us?
2) • Climate Change • Wegener Found evidence of glaciers around the world. • Glaciers will leave scratches in rock when they move. Wegener found these scratches in South Africa. • Do we see glaciers in Africa today?
3) • A hypothesis that the continents are not in a fixed position and move over long periods of time. • Was the first hypothesis of its kind, developed by Alfred Wegener.
4) Who was Harry Hess and what did he contribute to Science?
4) • Harry Hess was a professor at Princeton University. He studied Wegener's work and believed some of his theories. • Hess discovered the mid-oceanic ridge. The mid-oceanic ridge is the largest mountain range in the world.
4) • Mid-oceanic ridges were then studied further to develop sea-floor spreading.
What is the Theory of Plate Tectonics? What three pieces of evidence support this theory?
5) • The theory of plate tectonics is the formation, movement, and interaction of the plates at boundaries. • Three Pieces of evidence are???
6) • 1) Earthquakes and Volcanoes • Data indicates that these events do not occur in random locations. Instead they are concentrated in belts. • Earthquakes and volcanoes are going to occur along plate boundaries. • These boundaries are places where two plates are converging, diverging, or sliding past one another (Transform)
7) • 2) Age of the Sea-floor • When geologist discovered the ages of the rock in the magnetic reversal, they realized that the rock close to the mid-oceanic ridge was younger than the material further away.
8) • 3) Magnetic Stripes • When the rock is being made the iron will align itself. As soon as the rock cools it is held in place. They noticed that iron in the rock on the same side of the plate had changed in some locations. • This tells us that new material is being made at mid-ocean ridges.
9) Types of Plate Boundaries • Take out your Note Packet!!!
10) Chart on page 179 • Take out your chart!!!
11) Three hypothesis of plate movement • 1) Mantle Convection • According to the mantle convection hypothesis, the convection currents in the asthenosphere are moving the plates along with it as it convects.
11) • 2) Ridge Push • The new rock made at the ridge is less dense and more Buoyant than the rocks around it. As this new material cools and ages it becomes much more dense. • Gravity will then cause this old, dense rock to slide away from the ridge.
11) • 3) Slab Pull • The edge of the subducting plate is much older and heavier than the mantle, so it continues to sink, pulling the rest of the plate along with it.
12) What is Pangaea • Evidence indicates that around 250 million years ago, all the continents were a single landmass called Pangaea. • Pangaea formation is not completely understood. Geologist can not use ocean floor data because it is recycled roughly every 200 million years.
13) What is a craton • The ancient core of the Continents • One example of a craton is here in North America, which is exposed at the surface in most of eastern Canada. The part of the craton exposed is called the Canadian shield
Deep-Sea Sediments • Deep sea Sediments can be added to the edges of a continent when an oceanic plate is subducted under and continental plate. • Some of the sediment on the ocean floor will be scraped off and left behind as growth material on the edge of the contintent.
Igneous Rocks • Plutons formed from magma that rises from beneath earths surface will add material to the continents. • Any type of volcano is going to add material to the continents.
River Sediment • Rivers that flow across continents will erode material as they travel. These sediments which will be carried and eventually deposited, will build up along the edges of continents. • The Mississippi river delta in an example.
Terranes • A terrane is a large block of lithosphere plate. They usually travel great distances and attach themselves to pieces of the continents. • Geologist use three characteristics to idenitfy and terrane • 1) have major faults on all four sides • 2) Rocks and fossils are different than the rest of the continents • 3) Magnetic record does not match the other rock around it.
