Ridge Push

Force exerted on ocean lithosphere due to rising material below the mid-ocean ridge

Magnetometer

Instrument that measures small changes in magnetic fields

Continental Slope

Relatively steep portion of continental margin connecting the shallow continental margin with the deep ocean basin

Abyssal Plain

Relatively flat area of the deep ocean basin underlain by ocean lithosphere

Rift Valley

Long, narrow depression with parallel mountains on either side found along developing and mature divergent plate boundaries

Slab Pull

Force exerted on ocean lithosphere due to the weight of subducting ocean lithosphere

Seamount

Conical-shaped underwater volcanic mountain

Isochron

Line on a map connecting points of equal age

Guyot

Flat-topped seamount

Pangaea

Ancient supercontinent made up of all of today's continents

Fossils

Preserved remains of ancient organisms found in rocks

Sea floor spreading

Process in which older ocean lithosphere moves away from the mid-ocean ridge as new ocean lithosphere forms along the mid-ocean ridge

Moho

Boundary between Earth's crust and mantle

Continental Shelf

Relatively flat portion of continental margin covered by shallow ocean water

Subduction

Process in which ocean lithosphere plunges back into the asthenosphere under other lithosphere

Trench

Long, deep canyon on the ocean floor that forms where ocean lithosphere is subducting, typically the deepest parts of oceans

Plates

Large, slow-moving pieces of the Earth's lithosphere

Convergent

Plate boundary where the two plates move toward one another

Continental Margins

The edges of continents, parts of which are under relatively shallow ocean water, and are underlain by continental lithosphere

Volcanic Island Arc

Chain of volcanic islands bordering an ocean trench and formed by subduction

Asthenosphere

Middle part of the mantle below the lithosphere that exhibits the property of plasticity

Seismic Waves

Energy waves given off during earthquakes that are used to study the layers of the Earth

Plate Tectonics

Theory describing how the continents move and why there are earthquakes, volcanoes, and mountain ranges in certain areas

Divergent

Plate boundary where the two plates move away from one another

Plasticity

Ability of a solid to flow slowly and change shape

Continental Rise

Gently sloping pile of sediments at the edge of the continental margin marking the boundary between the continental and ocean lithospheres

Continental Volcanic Arc

Volcanic mountain range along the edge of a continent bordering an ocean trench and formed by subduction

Paleomagnetism

Ancient magnetic field of the Earth preserved in igneous rocks when they crystallized from magma

Hot Spot

Volcanic activity caused by a rising plume of hot material through the asthenosphere such as occurs at Hawaii and Yellowstone

Transform

Plate boundary where the plates move side-to-side past one another

Lithosphere

Solid, rigid top part of the Earth divided into numerous plates that slowly slide around the surface of the Earth

Convection

Movement of heat energy through a substance in which the molecules of the substance move from one area to another

Mid-ocean ridge

Long mountain chain along the ocean floor in which new ocean lithosphere is formed by seafloor spreading

Magnetic Reversal

A 180-degree flip in Earth's magnetic field