Science Internal Structures of Earth PDF

Science **Internal Structures of Earth** **Inner Core** - Center and hottest layer - 1,200 kilometers (746 miles) thick - Solid (due to extreme pressure) - Made up of iron and nickel with temperatures up to 5,500 ˚C **Outer Core** - Liquid - 2,300 kilometers (1,429 miles) thick...

Science **Internal Structures of Earth** **Inner Core** - Center and hottest layer - 1,200 kilometers (746 miles) thick - Solid (due to extreme pressure) - Made up of iron and nickel with temperatures up to 5,500 ˚C **Outer Core** - Liquid - 2,300 kilometers (1,429 miles) thick - Made up of iron and nickel with temperatures around 4000 ˚F -- 9000 ˚F **Mantle** - Approximately 2, 900 km thick - Semi-liquid - Made up of magma - Temperature is between 1600 ˚F -- 4000 ˚F **Asthenosphere** - Zone of Earth\'s mantle lying beneath the lithosphere is believed to be much hotter and more fluid than the lithosphere. - The asthenosphere extends from about 100 km (60 miles) to about 700 km (450 miles) below Earth\'s surface **Mantle and Asthenosphere** - An upper layer called Asthenosphere is responsible for the movement of plates. - Composed of mostly silicon, oxygen, magnesium and iron. - Texture is plastic like which has the characteristic of a solid but flows like a liquid when under pressure - Approximately 2885 km thick - Has large convection currents that drive the movement of the plates **Crust** - Outer layer where we live - Thickness is around 0 -- 60 km - Solid **Two Layers:** - Oceanic (denser and thinner and mainly composed of basalt) - Continental (less dense, thicker, and mainly composed of granite) **Lithosphere** - The solid, outer part of Earth. - It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below **Conorod discontinuity** - Between the upper and lower crust **Mohorovicc discontinuity** - Between the lower crust and upper mantle **Guttenberg discontinuity** - Between the lower mantle and outer core **Compositional Layers** - Crust (0-45 km) - Mantle (45-2900 km) - Core (2900-6371 km) **Mechanical Layers** - Lithosphere (solid) - Asthenosphere (plastic) - Mesosphere (solid) - Outer core (molten) - Inner core (solid) **Plate Tectonics** - Earth's surface is divided into a few large, thick plates that move slowly and change in size - Large, mobile slab of rock that is part of the earth's surface, bounded on four sides by weak plane surfaces - Consists of crust and upper part of the mantle **Tectonic Plates** - A massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere **Theory of Plate Tectonics** - states that the Earth\'s solid outer crust, the lithosphere, is separated into plates that move over the asthenosphere, the molten upper portion of the mantle. Oceanic and continental plates come together, spread apart, and interact at boundaries all over the planet - Developed from the 1950s through the 1970s - Plate tectonics is the modern version of continental drift, a theory first proposed by scientist Alfred Wegener in 1912. Wegener didn\'t have an explanation for how continents could move around the planet, but researchers do now **Plate Boundaries** - Threshold between 2 or more plates - Types: Convergent, Divergent and Transform **DIVERGENT BOUNDARY (Make new crust)** - **MOVES AWAY FOR EACHOTHER** - When two plates move apart magma surfaces form a NEW crust (usually oceanic) - continental rift zones (landmass splits into two or more segments) - mid-ocean ridges (sea floor is elevated) **DIVERGENT BOUNDARIES (Make the new crust: Sea Floor Spreading Oceanic-Oceanic)** - As magma rises and cools, iron and magnesium minerals align themselves to the Earth's magnetic field - "Magnetic Stripes" are formed - The Earth's magnetic field reverses polarity - Magnetic stripes are mirrored on each side of the mid-ocean ridge - Results: Mid-ocean ridges surrounded by new oceanic crust, the newest crust is closest to the rift zone. - ex. Mid-Atlantic Ridge, East Pacific Rise **Divergent Boundaries** **Rift Valley: continent-continent** - Youngest rocks form at the ridge - Older rocks are further from the ridge - Oldest rocks are located at subduction zones - Results: Young plate boundaries, rift valleys that may eventually fill with ocean water creating a new ocean, and then it becomes an oceanic-oceanic divergent boundary/mid-ocean ridge. - ex. Great Rift Valley in Africa, Lake Superior in North America (ancient/dormant rift) - Iceland has a divergent plate boundary running through its middle **Divergent Boundary** - **Oceanic -- Oceanic Mid Ocean Ridge (Seafloor Spreading)** - **Continental -- Continental Rift Valley** **CONVERGENT PLATE BOUNDARY** - **PLATES COLLIDING** - Destroys old crust and forms new mountains **Three types of convergent boundaries:** **Continental -- continental** - Two continental plates meet head-on - Since neither plate is stronger than the other, they crumple and are pushed up. This can lead to the formation of huge, high mountain ranges such as the Himalayas. - Results: Folded Mountains on Land. ex. Himalayan Mts., the Alps in Europe, the Appalachian Mts. (ancient orogenies or mountain building events) in the Eastern United States **Continental -- oceanic** - Oceanic plate sinks beneath continental plate - Subduction causes the formation of deep ocean trenches such as the west coast of South America - The rocks pulled down under the continent begin to melt. Sometimes the molten rock rises to the surface, through the continent, forming a line of volcanoes. **Ocean-continent convergence**: Trench & Coastal Volcanoes - Results: Subduction zone, basaltic oceanic crust is more dense than granitic continental crust. - Deep Ocean Trenches, Stratovolcanoes, and Volcanic Mountains on Land. - ex. Cascade Mountains in the Pacific Northwest US and the Andes Mountains in South America **CONVERGENT BOUNDARIES** Plates colliding: Subduction Zones - Denser oceanic plates always subduct beneath less dense continental plates - Subduction Zones: where ocean plates slide under another plate - Creating magma that moves upward, pushing up the land above it. - Magma/lava solidifies into intrusive/extrusive igneous rock ν Heat from the magma can change the rock around it. Rock that recrystallizes without melting becomes metamorphic rock. **Ocean-ocean convergence** - Subduction zone. - Deep Ocean Trenches, Island Arcs, Undersea Volcanism. - ex. Mariana Trench, Japan, Aleutian Islands (Alaska), Philippines, Sumatra (2004 Tsunami). **Convergent Boundaries** - Continental -- Oceanic Continental Volcanic Arc (Trenches) - Oceanic -- Oceanic Volcanic Island Arc (Trenches) - Continental -- Continental Mountain Belt Conclusion: **3 types of Plate Boundaries:** 1. **Convergent** - Towards each other - -\>\