Plate Tectonics

Alfred Wegener

A German meteorologist who proposed a hypothesis in 1915 that stated that all the continents were once joined together in a single land mass in the past and they have moved apart since.

Vine and Matthews

two graduate students who used the pattern of geomagnetic reversals from the ocean floor support ideas of seafloor spreading.

Harry Hess

Princton geologist who proposed Sea Floor Spreading in 1962 as the mechanism for Pangea's break-up

Tharp and Heezen

Creators of the first world ocean floor map & discovered the central rift valley (runs through the Mid-Atlantic Ridge)

Lithosphere

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

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.

Granite

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

Basalt

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

continental crust

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

oceanic crust

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

Continental Drift Hypothesis

hypothesis states that at one point in time, all the continents on Earth were together in a large land mass called Pangaea and have since moved apart.

Plate Tectonic Theory

Describes and provides evidence for the existence and movement of Earth's plates.

Continental Volcanic Arc

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

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.

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.

Transform Boundary

two plates slide past each other

Divergent Boundary

Plates that are moving away from each other.

Collisional Mountain Ranges

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

hot spots

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

pole reversal

a switch in the direction of Earth's magnetic field so that the magnetic north pole becomes the magnetic south pole and the magnetic south pole becomes the magnetic north pole.

reverse polarity

A magnetic field opposite to that which exists at present.

normal polarity

a magnetic field that is the same as that which exists at present

Paleomagnetism

The alignment of magnetic minerals in rock that form a historical record of the location and polarity of Earth's magnetic poles

Pangea

The name of the supercontinent. Means "all land". Existed about 250-200 million years ago.

pillow basalt

round blobs of basaltic lava cooled in water (mid-ocean ridge)

rift valley

A shallow valley formed as plates pull lithosphere apart.

Sea Floor Spreading

The theory proposed by Harry Hess in 1962. Convection currents in the asthenosphere allows lithosphere on top to separate and new sea floor to form, in other places the lithosphere crashes together and subduction takes lithosphere back into mantle. Continents ride along as part of the lithosphere as it separates.

Sonar

A device that determines the distance of an object under water by recording echoes of sound waves

subduction

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

Tectonic Plate

A block of lithosphere that consists of the crust and the rigid, outermost part of the mantle

Trench

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

upwelling

the movement of magma towards the surface at divergent boundaries

mid-ocean ridge

An underwater moutain chain where new ocean floor is formed

Crust

The thin and solid outermost layer of the Earth above the mantle

Mantle

The layer of hot, solid material between Earth's crust and core.

core

The central part of the earth below the mantle

Moho

boundary between crust and mantle

Mesosphere

The strong, lower part of the mantle between the asthenosphere and the outer core

Peridotite

Dense, dark igneous rock that makes up the mantle.

outer core

the liquid layer of the Earth's core that lies beneath the mantle and surrounds the inner core

inner core

A dense sphere of solid iron and nickel at the center of Earth

continental-continental convergent boundary

when two continental plates collide, with no subduction

oceanic-continental convergent boundary

When a more dense oceanic plate subducts under a less dense continental plate. Creates trenches and continental volcanic arcs.

oceanic-oceanic convergent boundary

When 2 oceanic plates converge against one another, causing the colder, denser, older plate to subduct. Creates trenches and volcanic island arcs.