Earths Crust Convection currents The Earths CRUST is

Earth’s Crust

Convection currents

The Earth’s CRUST is the outer most part of the Earth’s surface. • Average 32 km thick • Thickest point 70 km (in mountains) • Thinnest point 8 km (under ocean)

Lithosphere – all of the earth’s crust and part of the upper mantle. http: //www. allaboutspace. com/subjects/astronomy/plan ets/earth/Inside. shtml Asthenosphere – plastic like layer below the lithosphere. The ridged plates of the lithosphere “float” on the more plastic layer called the asthenosphere.

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Earth’s Mantle • Mantle: Under the crust is the rocky mantle, which is • • composed of silicon, oxygen, magnesium, iron, aluminum, and calcium. The upper mantle is rigid and is part of the lithosphere (together with the crust). The asthenosphere is a part of the upper mantle that exhibits plastic properties. It is located below the lithosphere (the crust and upper mantle), between about 100 and 250 kilometers deep. The lower mantle flows slowly, at a rate of a few centimeters per year (Called mesosphere).

MESOSPHERE

Earth’s Mantle • Convection (heat) currents carry heat • • from the hot inner mantle to the cooler outer mantle. The mantle is about 2, 750 km (1, 700 miles) thick. The mantle gets warmer with depth; the top of the mantle is about 870° C (1, 600° F) Towards the bottom of the mantle, the temperature is about 2, 2003, 700° C (4, 000 -6, 700° F) The mantle contains most of the mass of the Earth. The Gutenberg discontinuity separates the outer core and the mantle.

Earth’s Core • Core: The Earth has a iron-nickel • • core that is about 2, 100 miles in radius. The inner core may have a temperature up to about 7, 200°C (13, 000°F = 7, 500 K), which is hotter than the surface of the Sun. The inner core (which has a radius of about 1, 228 km (750 miles) is solid. The outer core is in a liquid state and is about 2, 260 km (1, 400 miles) thick. 4000 -5000°C

Earth’s Layers • Crust: Thin, hard outermost • • • layer Lithosphere: crust and upper mantle; RIGID and hard Asthenosphere: upper mantle that is more flowing (lithosphere/crust floats on it) Mesosphere (Lower Mantle) Outer Core Inner Core Mantle

Plate tectonic – theory that Earth’s crust and part of the upper mantle are broken into sections called plates. Continental drift – idea that continents have moved slowly to their current positions due to convection currents in the mantel. Pangea – the idea that the all land masses on earth were once a single large land mass.

Early Case for Continental Drift. Alfred Wegener (F. B. Taylor & H. H. Baker) • Continental coastlines fit together • • – 1620 Sir Francis Bacon: Africa and S. America Rocks & structures indicated that continents joined – Pangea- supercontinent of the late Paleozoic • Separated into Laurasia & Gondwanaland Fossil evidence- Glossopteris & Mesosaurus Late Paleozoic glaciation Skepticism about Continental Drift – Problem of driving mechanism

Continental Drift • Alfred Wegener 1912 • Pangaea (ALL EARTH) • Evidence: – Continents FIT together like the pieces of a puzzle – Fossils – Rocks & structures – Paleoclimate

Continental Drift • Alfred Wegener 1912 • Pangaea (ALL EARTH) • Evidence: – Continents FIT together like the pieces of a puzzle – Fossils – Rocks and structures – Paleoclimate

Continental Drift • Alfred Wegener 1912 • Pangaea (ALL EARTH) • Evidence: – Continents FIT together like the pieces of a puzzle – Fossils – Rocks and structures – Paleoclimate

Ocean floor spreading – theory that hot less dense material below Earth’s crust rises toward the surface at the mid-ocean ridges. Then, it flows sideways, carrying the seafloor away from the ridge in both directions. http: //geology. com/nsta/divergent-boundary-oceanic. gif Convection current – unequal distribution of heat in the mantel causes a net movement in a circular motion.