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Transcript
Earth Science The Formation of Soil Parts of the Earth • The crust of the Earth is an extremely thin, less-dense solid covering over the mantle—it essentially floats on top of the mantle • The mantle makes up the majority of the Earth, and surrounds a small core of iron. Parts of the Earth Structure of the Earth Parts of the Earth • The outermost portion of the mantle is solid. • The crust and solid outer mantle are collectively known as the lithosphere. • The asthenosphere is a thin layer below the outer mantle capable of plastic flow. Parts of the Earth Structure of the Earth Plate Tectonics • Plate tectonics is the concept that the outer surface of the Earth is made of large plates of crust and outer mantle that are slowly moving over the surface of the liquid outer mantle. – Heat from the Earth causes the slow movement. – Plates are pulling apart in some areas, and colliding in others due to convection cells. – These building processes are counteracted by processes tending to make elevated surfaces lower—i.e.erosion. Plate Tectonics Tectonic plates Plate Tectonics • Evidence that plates are moving: – Earthquakes – Volcanoes • both happen at plate boundaries • The asthenosphere provides the plates with a surface on which they can move—it is pliable because it is hot. Plate Tectonics • Heat from Earth’s inner and outer cores is transferred through the mantle by a process called mantle convection. – The mantle moves the plates along with it as it convects. Plate Tectonics Subduction Destructive margin Mid oceanic ridge Constructive margin Convection cells Plate Tectonics • A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle. – when they reach shallow depths, they are thought to be the cause of volcanic centers known as hotspots. – Hawaii was formed by mantle plumes. Plate Tectonics Mantle plume Geographic formations • Where 2 plates are pushing against each other, mountains form. • Where 2 plates are pulling away from each other, cracks in the lithosphere form. Geographic Formations • Mountain ranges form where 2 plates come together. – Himalayas – Cascades – Andes Diversity • Diverse geographic formations lead to ecological diversity. • Ecological diversity leads to biological diversity (biodiversity). – organisms have adapted (evolved) to live in a certain geographic region. • Examples: – – – – Artic hare Deep water fish Mountain goats Bison Diversity • Geographic formations can lead to isolation of populations. – Examples: • Islands • Mountain ranges • Bodies of water – Isolation of populations leads to speciation • This means that the population can only reproduce with its own kind. • Example: • Eastern Meadowlark vs. Western Meadowlark • Kiiwii in Hawaii Geographic Formations • Think of the effect of elevation on climate and vegetation. Soil Formation • Although mountains are constantly being formed by converging plates, erosion is continually breaking down the mountains. • Due to this building and breaking down, soil is formed. – The type of soil depends on the source and the amount of weathering it has experienced.