Earth's Layers & Plate Tectonics

earthquake

A movement or trembling of the ground that is caused by a sudden release of energy when rocks along a fault move. Often happens along the edges of transform boundaries

volcano

A weak spot in the crust where magma comes to the surface, often occurs where an oceanic plate subducts under a continental plate

Pangaea

Alfred Wegner's name for a supercontinent that existed about 245 million years ago, and from which all present day continents are formed.

Convection Currents

Circular currents in the mantle caused by the magma being heated by the core of the Earth and cooling as it rises. This leads to the cooler mantle falling back toward the center where it is again heated by the core.

mountains

Formed by two continental plates colliding and forcing each other upwards.

Tectonic Plates

Huge pieces of lithosphere (crust and mantle) that move around on top of the asthenosphere (lower mantle).

magma

Molten rock beneath Earth's surface. Once it rises above the surface, it is called lava.

oceanic-continental boundary

The boundary between an oceanic and continental plate. These are all convergent (no divergent examples exist). These result in the more dense oceanic crust subducting under the continental plate. This can result in volcanoes being formed in the continental plate.

Convergent Boundary

The boundary between two colliding tectonic plates

continental-continental boundary

The boundary between two continental plates. Convergent boundaries can result in mountain ranges. Divergent boundaries can result in rift valleys although these are mostly extinct and no longer moving.

oceanic-oceanic boundary

The boundary between two oceanic plates. Divergent boundaries can result in sea-floor spreading and convergent boundaries can result in volcanic island arcs.

Divergent Boundary

The boundary between two tectonic plates that are moving away from each other

Transform Boundary

The boundary between two tectonic plates that are sliding past each other

Lithosphere

The cool, rigid, outermost layer of the earth that is divided into enormous pieces called tectonic plates. It is made up of the crust and the top part of the mantle.

mantle

The layer of hot, solid material between Earth's crust and core. (the upper part is found as part of the lithosphere while the bottom is part of the asthenosphere)

Sea Floor Spreading

The process by which new oceanic lithosphere (sea floor crust) forms at mid-ocean ridges. As the new crust forms, it pushes existing crust in the opposite direction away from the ridge.

Asthenosphere

The soft, lower layer of the mantle on which the lithosphere floats.

Continental Drift

The theory proposed by Alfred Wegener that today's continents were once part of a single landmass that broke into pieces that drifted apart from one another into their present day locations. It also suggests they are still drifting.

Plate Tectonics

The theory that pieces of Earth's lithosphere are in constant motion, caused by convection currents in the mantle.

Trench

a long steep-sided dip in the ocean floor caused by an oceanic plate sinking below a continental plate and pulling a bit of the continental plate with it

Alfred Wegener

he proposed the theory of continental drift that states that all land on the earth was once a single mass but eventually broke apart from one another and drifted away

core

the HOTTEST and MOST DENSE layer of Earth, found in the center of Earth

Subduction Zone

the area where an oceanic plate sinks down into the asthenosphere at a convergent boundary (usually between continental and oceanic plates)

Plate boundary

the region where two tectonic plates are in contact

continental crust

thicker, less dense, older part of Earth's crust that makes up the continents. Made mostly of granite. ARROW ON THE RIGHT SIDE OVER THE MOUNTAINS

oceanic crust

thinner, more dense, younger crust that makes up ocean floor. Made mostly of basalt. ARROW ON THE LEFT SIDE OVER THE WATER