Will California really ever fall off into the ocean? You should be able to answer this question by the end of the power-point.

Transcription

1 Plate Tectonics

2 Will California really ever fall off into the ocean? You should be able to answer this question by the end of the power-point.

3 Continental Drift Developed in 1912 by Alfred Wegner, a German meteorologist. Continental Drift proposed that Earth s continents had once been joined as a single landmass that broke apart and sent the continents adrift. Wegner called the supercontinent Pangaea which means all the earth in Greek. Pangaea broke up 200 mya. The northern half of Pangaea was referred to as Laurasia and the southern portion is known as Gondwanaland.

4 Evidence from rock layers When examining the rock layers of where the continents were connected during Pangaea, it was discovered that the rocks were of the same TYPE and AGE!

5 Fossil Evidence Wegner found similar fossils of several different animals and plants that once lived on or near land had been found on widely separated continent. The dinosaurs found could NOT swim across oceans, therefore continents had to be connected!

6 The Continents fit together like puzzle pieces:

7 Coal deposits, made accumulation of swamp plants, were found on Antarctica. Climatic Evidence: Glacier deposits were found on Africa, India, South America and Australia. For example, the Glossopteris was a fern-like shrub and was found in South America, Antarctica and India. This plant grew in Temperate Climates, which were places closer to the equator.

8 Seafloor Spreading Sea-floor spreading is the process in which the ocean floor is extended when two plates move apart. As the plates move apart, the rocks break and form a crack between the plates. Earthquakes occur along the plate boundary. Magma rises through the cracks and seeps out onto the ocean floor like a long, thin, undersea volcano or magma slowly come up and cools forming NEW OCEAN FLOOR!

9 Paleomagnetism is the study of the record of the Earth s magnetic poles preserved in various magnetic minerals, such as hematite in the ocean floor, through time. This supports the theory of continental drift because it demonstrates that periods of pole reversals align perfectly on the ocean floor. It demonstrates an identical pattern on both sides of the spreading centers. This demonstrates plate motion! Paleomagnetism

10 Evidence of continental drift (Summary) 1. Plates/continents fit together like puzzle pieces 2. Fossil evidence- dinosaurs and plants on Antarctica 3. Same type and ages of rocks found on Africa and South America 4. Seafloor Spreading- new rock created along the ocean floor 5. Paleomagnetism- shows a pattern of identical pole reversal on both sides of a spreading center. The Dwyka Tillite (rocks layers shown) correlates with similar rocks in South America, India, Australia, and Antarctica. Alfred Wegener considered this uplifted rock layer to be evidence of continental drift.

11 Layers of the Earth A. Crust- solid, 5-70 km thick Two Types of Crust: Oceanic- ocean floor, more dense then because of more iron Continental-dry land B. Moho- boundary between mantle and crust Lithosphere- upper part of the mantle, almost like crust Asthenosphere- softer layer under lihtosphere C. Mantle-(lower) melted, plastic magma D. Outer Core- liquid metal E Inner Core- solid metal (iron and nickel)

12 Convection currents in the mantle -The plasticity of the mantle allows the plates to glide and move along the mantle creating mountains, trenches and new land. -Heat from the core and the mantle itself causes convection currents to be created in the mantle. -The warmer magma at the bottom of the thick mantle is warmer because it is closer to the core. Warm magma is less dense and rises to the top of the mantle, then it cools and sinks again, creating a constant circulation in the mantle.

13 This diagram shows how the moving plate boundaries move and create different landforms. Convection Currents

14 Which plate do we live on? Divergent creates new ocean floor! Convergent creates mountains and volcanoes!

15 Plate Tectonics- the study of the movement of thin slabs of crust called tectonic plates. Three types of plate boundaries: 1. Convergent- two plates coming together 2. Divergent- two plates separating 3. Transform- two plates sliding past each other.

16 California lies on a strike-slip fault. So, will it ever fall off into the ocean? NO! The only possibility is that the western half of California will float north (up the coast of the U.S)

17 Three Types of Convergent Plate Boundaries A. Continental-Continental- Creates Mountains. (Example?) Oceanic crust sinks, why? B. Oceanic-Oceanic- More dense plate sinks & melts. Magma rises up and creates island volcanoes. (Ex: Fiji) C. Continental-Oceanic-oceanic sinks and comes to the surface and creates land volcanoes.(example:???)

18 Volcanoes and Plate Tectonics Volcano- a weak spot in the crust where magma comes to the surface. There are about 600 active volcanoes on land and many more beneath the sea. - Ring of Fire: an area of active volcanoes that form along the Pacific Plate boundary.

19 The Tectonic Plates of the World Tectonic Plates of the World