Chapter

tectonic plate

A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest.

Compression

Compression- the action of compressing or being compressed.

continental drift

Continental drift- is the movement of the Earth's continents relative to each other, thus appearing to "drift" across the ocean bed. The speculation that continents might have 'drifted' was first put forward by Abraham Ortelius in 1596.

crust

Crust - In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle.

divergent boundery

In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other.

inner core

Inner Core - The Earth's inner core is the Earth's innermost part and according to seismological studies, it has been believed to be primarily a solid ball with a radius of about 1220 kilometers

subduction zone

subduction zone- In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate and sinks into the mantle as the plates converge. Regions where this process occurs are known as subduction zones.

tension

tension- Stress created as a result of two tectonic plates moving apart.

transform boundary

transform boundary- A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction.

lithosphere

Lithosphere- The lithosphere is the solid outer section of Earth, which includes Earth's crust (the "skin" of rock on the outer layer of planet Earth), as well as the underlying cool, dense, and rigid upper part of the upper mantle. The lithosphere extends from the surface of Earth to a depth of about 44-62 mi (70-100 km).

normal fault

Normal Fault. A geologic fault in which the hanging wall has moved downward relative to the footwall. Normal faults occur where two blocks of rock are pulled apart, as by tension. Compare reverse fault.

plate tectonics

Plate tectonics- is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere.

reverse fault

Reverse faults- are exactly the opposite of normal faults. If the hanging wall rises relative to the footwall, you have a reverse fault. Reverse faults occur in areas undergoing compression (squishing).

sea-floor spreading

Seafloor spreading- is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics.

stress

Stress is conventionally defined as a force acting on some area . Stress is defined as a force acting on some area

strike-slip fault

Strike-slip faults are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally. If the block opposite an observer looking across the fault moves to the right, the slip style is termed right lateral; if the block moves to the left, the motion is termed left lateral.

asthenosphere

The asthenosphere- is the highly viscous, mechanically weak and ductilely deforming region of the upper mantle of the Earth. It lies below the lithosphere, at depths between approximately 80 and 200 km (50 and 120 miles) below the surface.

mantle

mantle - The region of the interior of the Earth between the core (on its inner surface) and the crust (on its outer). Note: The mantle is more than two thousand miles thick and accounts for more than three-quarters of the volume of the Earth.

mesosphere

mesosphere- the region of the earth's atmosphere above the stratosphere and below the thermosphere, between about 30 and 50 miles (50 and 80 km) in altitude.

outer core

outer core- of the Earth is a fluid layer about 2,300 km (1,400 mi) thick and composed of iron and nickel that lies above Earth's solid inner core and below its mantle. Its outer boundary lies 2,890 km (1,800 mi) beneath Earth's surface.

convergent boundary

convergent boundary- In plate tectonics, a convergent boundary, also known as a destructive plate boundary (because of subduction), is an actively deforming region where two (or more) tectonic plates or fragments of the lithosphere move toward one another and collide.

core

core - In geology, the central region of the Earth; it extends fourteen hundred to eighteen hundred miles from the Earth's center. Note: The core is made primarily of iron and nickel and has two parts — an inner solid core and an outer liquid core.

folding

folding- A bend in a layer of rock or in another planar feature such as foliation or the cleavage of a mineral. Folds occur as the result of deformation, usually associated with plate-tectonic forces

fault

A fault - is a crack in the Earth's crust. Typically, faults are associated with, or form, the boundaries between Earth's tectonic plates. In an active fault, the pieces of the Earth's crust along a fault move over time. The moving rocks can cause earthquakes.