All terms in this list:

Core: the dense center of the earth made of solid and molten iron and nickel

Mantle: the layer of earth that surrounds the core; made of both molten magma and solid rock

Crust: the thin, solid, rocky outermost layer of the earth

Viscosity: the ability of a substance to resist flowing

Tectonic Forces: forces generated from within the earth that result in uplift, movement, or deformation of the earth's crust

Richter Scale: he scale used to measure the magnitude or strength of an earthquake

Focus: the point inside the earth where rock first moves, starting an earthquake

Epicenter: the point on the earth’s surface directly over the focus of an earthquake

Convection Current: he circular flow of magma within the molten part of the mantle as it heats up and cools down

Oceanic Trench: geologic feature formed in the oceans at convergent boundaries where subduction zones exist

Deformation: the process of physically changing the earth’s crust as a result of tectonic forces

Continental Margin: the edges of the continents below sea level that represent the shallowest parts of the oceans

Plate Boundary: an area on the earth’s surface where the edges of tectonic plates are interacting

Subduction: he geologic process by which one tectonic plate is forced downward into the mantle under another tectonic plate forming an oceanic trench

Volcanic Arc: an arcing chain of volcanic islands or volcanic mountains formed by the subduction of an oceanic plate into the mantle under another tectonic plate

Aleutian Islands: an arc-shaped chain of small volcanic islands off the coast of Alaska formed by subduction processes along an oceanic-oceanic convergent boundary

Cascade Mountain Range: active volcanic mountain range located in the Northwest United States formed by the subduction zone between the Juan de Fuca and North American plates that produces volcanic hazards for California

Mid Ocean Ridge: underwater mountain range that is hundreds of miles long in the middle of the ocean providing evidence that Earth's tectonic plates are moving away from each other at a divergent plate boundary as mantle magma rises to form new crust

Mid Atlantic Ridge: mid ocean ridge in the middle of the Atlantic Ocean responsible for pushing apart the continents of Africa and S. America

Plate Tectonics: the theory that the earth’s surface is made of large sections of crust that move and interact with each other

Ring of Fire: an area of high subduction activity and frequent volcanic eruptions surrounding the Pacific Plate

Basaltic Magma: magma having low viscosity, low silica content (SiO2), small amounts of dissolved gases, and high concentrations of iron and magnesium that produces quiet, nonexplosive, voluminous eruptions of thin, fluid lava

Granitic Magma: very thick and sticky magma having high viscosity due to cooler temperatures, high silica content (SiO2), high gas content, and low concentrations of iron and magnesium that produces extremely violent volcanic eruptions

Continental Drift: the theory originally proposed by Alfred Wegner that the major landmasses of the earth were once part of one large single super continent that broke apart 200 million years ago

Differentiation: the process of Earth materials separating and sorting by density resulting in a layered structure with the densest material (Fe & Ni) settling in the core

Tectonic Plates: a large section of the earth’s crust that moves and carries everything on it

Hotspot: a stationary, high temperature area of melting within the earth’s mantle that can last for several millions of years where super heated mantle magma rises towards the surface

Rift Valley: a long, narrow rip or opening, made by the stretching, pulling, or splitting apart of the earth’s crust along divergent plate boundaries through which mantle magma reaches the surface adding new crust to the edge of a tectonic plates

Seafloor Spreading: the theory that oceans widen (open up) and continents are pushed apart as new crust is formed at mid-ocean ridges

Paleomagnetism: a record of the Earth's magnetic field preserved by the alignment of magnetic minerals in the rocks of earth’s crust at the time that the rocks were formed at mid ocean ridges