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Earth's Inner Structure and Plate Tectonics
- 1. Prepared by: Karen Grace S. Manaay
- 2. . . . . . . . . . . . . . . . . . . . . . Inner Core Outer Core Mantle (Inner and Outer) Crust Earth’s Inner Structure
- 3. . . . . . . . . . . . . . . . . . . . . . Approximate Depths from the Surface ~30 km (~ 18 miles) ~2,900 km (~1,800 miles) ~ 5,200 km (~ 3,000 miles) ~ 6,400 km (~ 4,000 miles)
- 4. . . . . . . . . . . . . . . . . . . . . More Info! Surface Temperature ~ 0 °C Mohorovicic Discontinuity Temperature ~ 1,000 °C Gutenberg Discontinuity Temperature ~ 3,700 °C Outer/Inner Core Boundary Temperature ~ 4,300 °C Inner Core Temperature ~ 5,000 – 7,000 °C DT/D(time) ~ 500 °C/(3B Years) Rocky Plastic Mg, Fe, Al, Si, O Liquid Fe, S Solid Fe Radioactivity in the core Keeps things warm!
- 6. Movement of the Plates Over Time Permian 248 million years ago Triassic 206 million years ago Jurassic 206 million years ago Cretaceous 65 million years ago Present Day
- 7. Plate Tectonics The theory that the Earth’s outermost layer is fragmented into a dozen or more large and small plates that move relative to one another as they ride on top of hotter, more mobile material.
- 8. What Are Tectonic Plates? • A plate is a large, rigid slab of solid rock. • Plates are formed from the lithosphere: the crust and the upper part of the mantle. • The plates “float” on the slowly flowing asthenosphere: the lower part of the mantle. • The plates include both the land and ocean floor. • The Mohorovicic discontinuity or Moho is the boundary between the crust and the mantle.
- 9. Tectonic Plates Crustal plates, also known as tectonic plates, form the outer layer of the Earth. There are seven major plates and many smaller plates. Tectonic plates contain both the Earth's crust and the uppermost part of the mantle.
- 10. 2 Types of Tectonic Plates There are two types of tectonic plates. Continental plates are made primarily of granitic rocks and are much thicker and older. Oceanic plates are thinner, heavier, and younger. Together these plates form the lithosphere.
- 11. Continental Crustal Plates Composition Igneous, sedimentary, and metamorphic rocks form the continents. The basement rocks of the continents are granitic. The minerals in granitic rocks are lighter than the oceanic crust. The density of the continental crust is also less than the mantle.
- 12. Continental Crustal Plates Thickness The continental plates are between 25 and 70 kilometers thick. The thickest continental crust is located where great mountain ranges have formed like the Himalayas.
- 13. Oceanic Crustal Plates Thickness The oceanic crust is only about 10 kilometers thick but is much denser and heavier than the continental crust.
- 14. Oceanic Crustal Plates Composition Is mostly composed of different types of basalts. Geologists often refer to the rocks of the oceanic crust as “sima.” SIMA stands for silicate and magnesium, the most abundant minerals in oceanic crust. (Basalts are a sima rocks.)
- 16. OCEANIC CRUST CONTINENTAL CRUST Continental & Oceanic Crust
- 17. Different Types of Boundaries
- 25. Convection in the mantle Mantle convection describes the movement of the mantle as it transfers heat from the white-hot core to the brittle lithosphere. The mantle is heated from below, and cooled from above, and its overall temperature decreases over long periods of time. All these elements contribute to mantle convection.
- 26. Convection in the mantle The primary sources of thermal energy for mantle convection are three: (1) internal heating due to the decay of the radioactive isotopes of uranium, thorium, and potassium; (2) the long- term secular cooling of the earth; and (3) heat from the core.
- 28. A mantle plume can be defined as a narrow band of rock within the mantle that is hotter than its surroundings.
- 30. Divergent boundaries (also known as Constructive Boundaries) are places where two or more plates move away from each other. These boundaries can be found on continental or oceanic lithosphere.
- 31. Tensional stress operates between the tectonic plates at a divergent boundary, which causes the lithosphere at these locations to stretch and pull apart.
- 32. The process of divergence breaks up continental landmasses and supercontinents.
- 34. A divergent boundary may form beneath the continental lithosphere, where mantle convection cells cause the plates to push apart and form a Rift Valley.
- 35. Continental Rift Valley Is a region where the continental lithosphere is weakening and stretching apart. Given enough time, the rifting will continue to a point in which the continental lithosphere will become so thin, it will become predominantly enriched in the mantle plume materials. The East African rift valley is an example of an active continental rift valley.
- 37. SUSWA RIFT IN KENYA
- 39. A divergent boundary may also form beneath the oceanic lithosphere, where mantle convection cells cause the plates to push apart and form a mid-ocean ridge.
- 41. Mid- Ocean Ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics.
- 43. Mid-Atlantic Ridge Is a mid-ocean ridge located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world.
- 44. Mid-Atlantic Ridge • was discovered in the 1950s • its discovery led to the theory of seafloor spreading and general acceptance of Wegener's theory of continental drift. • The MAR separates the North American Plate from the Eurasian Plate in the North Atlantic, and the South American Plate from the African Plate in the South Atlantic. • These plates are still moving apart, so the Atlantic is growing at the ridge, at a rate of about 2.5 cm per year in an east-west direction.