Hon Plate Tectonics Ruggiero 24-25

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.

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

States that the earth's surface is broken into rigid tectonic plates that are in constant motion driven by convection

Volcanic Island Arc

chain of volcanic islands that form on oceanic crust, caused by partial melting of mantle due to the subduction of an oceanic plate beneath another oceanic one.

Continental Volcanic Arc

chain of volcanic mountains that form on continental crust, caused by partial melting of mantle due to the subduction of an oceanic plate beneath a continental one.

convection current

A rising and sinking loop of slow flowing mantle below and lithosphere above due to differences in density, temperature and pressure

Convergent Boundary

When plates move toward each other: sub-types are O-C subduction, O-O subduction, or C-C collision.

Transform Boundary

two plates slide past each other

Divergent Boundary

Plates that are moving away from each other.

Folded 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 rise up in essentially fixed locations not necissarily caused or associated with plate boundaries

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 most recent supercontinent. Means "all land". Existed about 250-200 million years ago.

rift valley

A shallow valley formed through extensional forces as magma swells the lithosphere and lithosphere pulls apart.

Seafloor Spreading Hypothesis

The hypothesis 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.

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 bending down top plate during subduction of two converging plates.

lower mantle

The dense, slow flowing lower part of the mantle between the asthenosphere and the outer core

outer core

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

inner core

A hot, 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.

Paleoclimate

climate in the geologic past

Mohorovicic Discontinuity

the boundary between Earth's crust and mantle

mantle transition zone

Boundary between less dense faster flowing asthenosphere and denser, slower flowing lower mantle. Zone is enriched in carbon and water squeezed out of subducting plates as the minerals recrystalize into denser crystalline structures as they enter lower mantle.

Lithosphere-Asthenosphere Boundary

the "LAB" is a boundary between the asthenosphere and lithosphere, a change in mechanical properties from rigid to ductile behavior within the mantle.

Core-mantle boundary

the "CMB" is a boundary between Earth's core and its mantle, about 2,900 km below Earth's surface. Also known as the Gutenberg discontinuity.

D-Double Prime Layer

the transition zone between the lower mantle and outer core that sometimes spawns diapirs of hotter, more fluid mantle

Diapir

mushroom shaped bodies of hot, more fluid rock that ascend within Earth's interior because they are less dense than the surrounding rock.

mantle plumes

relatively narrow tall structures of rising, hot, more fluid rock that rise within earth's interior because they are less dense than the surrounding rock. Some originate at great depth, perhaps at the mantle-core boundary. They cause hotspot volcanism.

geothermal gradient

the rate of change in temperature with depth in the geosphere. Approximately 25 degrees C/km

mantle wind

name given to the convection currents in mantle induced by subducting slabs of lithosphere that are responsible for changing the landscape of continents above

whole-mantle convection model

Cold oceanic lithosphere descends into the lowermost mantle, while two types of hot mantle plumes transport heat toward the surface. there is material transfer between the upper and lower mantle regions.

layer-cake convection model

lithosphere and asthenosphere recycle in convection loops above the mantle transition zone 660 km boundary and slow flowing, dense lower mantle layer convects and carries heat upward without mixing material with the asthenosphere.

xenoliths

Fragments of rock carried up in plumes without melting, able to preserve and inform us about the upper and lower mantle

slab pull

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

ridge push

a mechanism that contributes weakly to plate motion; it involves the oceanic lithosphere sliding down the oceanic ridge due to gravity "pushing" the plate along ahead of it

slab suction

a mechanism that contributes to plate motion and occurs as subduction induces downward mantle circulation that pulls both subducting and overriding plates toward a trench.