Unit 7 - Plate Tectonics (H)

accretionary wedge

accumulation of sediment "scraped" off the ocean floor during subduction of the oceanic plate, located between the trench and fore-arc basin

Anticline

an upward fold in rock formed by compression of Earth's crust

Asthenosphere

A mechanical layer of earth located within the mantle below the lithosphere, that has the ability to flow, so is called a plastic-solid.

back arc spreading

tensional forces caused by slab rollback and the collapse of the edge of the continent. As the slab collapses into the mantle, it can 'roll back'. This rollback can pull on the overriding plate, causing extension

back-arc basin

a basin that forms on the side of a volcanic arc away from the trench

Basalt

Predominant rock of the oceanic crust. Quartz poor igneous rock, high in magnesium and iron.

Basin and Range

parallel mountain ranges and valleys in between due to divergence

continental crust

part of outermost compositional layer of earth. Usually made of granite (mostly quartz and feldspar minerals)

continental volcanic arc

chain of volcanoes that form on land, caused by partial melting due to the subduction of an oceanic plate

convection current

A rising and sinking loop of slow flowing asthenosphere due to differences in density, temperature and pressure.

Convergent Boundary

When plates move toward each other: subtypes are O-C, O-O, or C-C.

deep layer model

Favors deep in the mantle. The lower acts like a lava-lamp w/ slow swelling & sinking pattern w/out much mixing. supports the deep subduction of the cold oceanic lithosphere.

Divergent Boundary

Plates that are moving away from each other.

felsic

Describes magma or igneous rock that is rich in feldspars and quartz and that is generally light in color.

Folded Mountains

Mountains formed when two plates carrying continental crust collide, deforming the rocks and earth with great force.

fore arc basin

depression in the sea floor located between a subduction zone and an associated volcanic island arc

Grabens

areas of land that have dropped down between faults

Granite

Predominant composition of continental crust. Igneous rock high in quartz, formed from partial melting.

Horst

a ridge of the earth's crust that has been forced upward between two faults and so is higher than the surrounding land

hot spots

plumes of very warm mantle material that rises up in essentially fixed locations.

layer-cake model

This model has two zones of convection- a thin, dynamic layer in the upper mantle and a thicker, sluggish one locate below. The downward convective flow is driven by the subduction of the cold, dense oceanic lithosphere.

lithosphere

A mechanical layer of earth which is rigid and brittle and breaks into segments. It includes the crust and very top of mantle.

Mafic

describes magma or igneous rock that is rich in magnesium and iron and that is generally dark in color, low in quartz

oceanic crust

part of outermost compositional layer of earth, usually made of basalt (magnesium and iron-rich igneous rock).

partial melting

the process by which different minerals in rock melt at different temperatures causing only certain mineral to turn to liquid at subduction boundaries

Ridge-Push

One of the mechanisms that moves plates. Gravity slides plates downslope from the higher elevation ridges at divergent boundaries.

rift valley

A shallow valley formed on land as plates pull the lithosphere apart.

slab rollback

The process of subducting slab pulling back from the trench that involves an older oceanic crust which is colder and denser than other slabs, subducting at a steep angle.

Slab-pull

a mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and "pulls" the trailing lithosphere along

subduction

Denser oceanic crust sinks down into the mantle beneath the less dense plate

suture

the line that marks where two continental plates fused during a continent-continent collision.

Syncline

A downward fold in rock formed by compression in Earth's crust

Transform Boundary

two plates slide past each other

Trench

Deep, steep valley on the ocean floor created by subduction.

upwelling

the movement of magma towards the surface at divergent boundaries

Volcanic Island Arc

Forms at an oceanic-oceanic convergent boundary. String of volcanoes that result from melting related to the subduction of the older, denser oceanic crust.

whole-mantle convection model

Cold oceanic lithosphere plate sinks deep w/in the mantle, while hot buoyant plumes transport heat towards the surface.**problem: w/ this model it would chemically mix up magma, & make the earth mantle heterogeneous mixture, when it's a Homogeneous.

Uniformitarianism

A principle that geologic processes occurred slowly over long periods of time in the past can be explained by current geologic processes

catasprophism

the idea that the earth's landforms occurred quickly and as the result of catasptrophes

playa lake

a flat area on the floor of an undrained desert basin (playa) that fills and becomes a lake after heavy rain