Theory of Plate Tectonics PDF

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Summary

Notes and vocabulary list of tectonics...

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Theory of Plate Tectonics Alfred Wegener observed the fit of these continents and tried to explain this and other data with continental drift. 

The fossil distribution is consistent with continental drift

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Earthquakes usually occur in discrete belts

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Ocean trenches and associated island arcs have numerous earthquakes

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Most tectonic activity occurs around plate boundaries, but sometimes happen in the middle of plates

Plate Movement: 

Divergent: two plates move apart relative to one another and magma fills the space between the plates.

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Convergent: two plates move toward one another, typically one plate slides under the other

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Transform: two plates move horizontally past one another

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Mid-ocean ridges are divergent plate boundaries and new oceanic lithosphere forms.

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Elevation of the seafloor decreases away from the ridge because the rock cools and contracts

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When rifts occur, the entire crust thins as it is pulled apart. The central rift becomes lower in elevation over time

Convergent Boundaries Two plates move towards each other and can contain oceanic and continental plates. 

Oceanic trenches, island arcs, and earth’s largest mountain belts form at convergent boundaries.

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Many of earth’s most dangerous volcanoes and largest earthquakes also occur along these boundaries

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Ocean-ocean convergent boundaries: two oceanic plates where one bends and slides beneath the other plate along an inclined zone

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As the plate subducts, the temperature increases and releases minerals. The water causes melting in the asthenosphere and the resulting magma is buoyant and rises to the overlying plate

Oceanic and Continental Plate 

Volcanoes form the same way they form on ocean-ocean boundaries on the overriding plate

How Do plates move and interact? Circulates material back and forth between the asthenosphere and the lithosphere 

By creation and destruction of the lithosphere, the earth transports heat to the surface

Earth’s Magnetic Field The inner core transfers heat and less dense material to the liquid outer core. 

Movement of molten iron is affected by the forces within earth’s rotation. Movement of liquid iron and electrical currents generates the magnetic field

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Lava erupts and the magnetic field is recoded by the iron-rich mineral magnetite contained within the rocks

Seamount Chains 

Hot spots push high temperature regions of magma and if the hot spot is moving relative to the hot spot, volcanism constructs a chain of volcanoes

 Abyssal Plains Mid-ocean ridges Seamounts Fracture Zones Continental Shelves Island arcs Gondwana Seafloor Spreading Tectonic activity/tectonics Lithosphere Spreading center Continental rift Subduction Subduction zone Oceanic trench Accretionary Prison Oceanic-continent boundary Continental Collision Transform Faults Driving force Slab pull

Ridge Push Mantle Convection

Fairly smooth surfaces in the ocean Broad, symmetrical ridges that cross the ocean basins. They are 2 to 3 km higher than the average depth of the seafloor Mountains in the ocean that do not reach sea level Cracks and steps that cross the seafloor mostly at right angles. Continents that continue outward from the shoreline under shallow seawater. Curving chains of islands The southern continent name when they were a single large super continent Contributed to Wegener’s observation and combined into the theory of plate tectonics Earthquakes, volcanoes, other processes that deform the crust Earth’s strong upper layer that is broken into a dozen or so fairly rigid pieces that are called tectonic plates Mid-ocean ridges Stretching of the crust causes large crustal blocks to drop down along faults The process of one plate sliding beneath another plate The zone around the downward-moving plate. Many large earthquakes occur in subduction zones. Form as the subducting plate bends down. Sediment and slices of oceanic crust collect in the trench. Material is being added over time to the wedge or prism shaped region Along this boundary, the denser oceanic plate subducts beneath the more buoyant continental plate Produces huge mountain ranges and high plateaus within continent-continent boundaries. Plates slip horizontally past each other and are associated with mid-ocean-ridges. The spreading direction must be parallel to transform faults and perpendicular to the spreading segments. A force that drives the movement that must exceed the resisting force. A significant force that moves plates faster, subducted plates move more quickly than those not subducted. The mid ocean ridge is higher than the ocean floor away from the ridge because lithosphere near the ridge is thinner and hotter. Gravity causes the plate to slide away from the topographically high ridge and push the plate outward. The asthenosphere is capable of flow. It experiences convection,

where hot material rises and cold sinks. Hot material rises at mid-ocean ridges, cools, and eventually sinks back into the asthenosphere at a subduction zone....