Chapter 7 Vocab

Inner core

, the innermost part of a core, specif. a solid sphere in the middle of the fluid core such as the iron-nickel core of the Earth.

Folding

A bend in a layer of rock or in another planar feature such as foliation or the cleavage of a mineral

Compression

A compression is a region in a longitudinal wave where the particles are closest together. Definition 2: Rarefaction. A rarefaction is a region in a longitudinal wave where the particles are furthest apart.

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

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

Reverse fault

A geologic fault in which the hanging wall has moved upward relative to the footwall. Reverse faults occur where two blocks of rock are forced together by compression. Compare normal fault. See Note and illustration at fault.

Divergent boundary

A tectonic boundary where two plates are moving away from each other and new crust is forming from magma that rises to the Earth's surface between the two plates.

Continental drift

A term, no longer used by geologists, that refers to the fact that continents are not stationary, but move across the Earth's surface

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

Earth's lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth. The lithosphere is subdivided into tectonic plates.

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.

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.

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.

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: In a medical or biological context stress is a physical, mental, or emotional factor that causes bodily or mental tension.

Tension

The act or process of stretching something tight. The condition of so being stretched. A force tending to stretch or elongate something. The partial pressure of a gas, especially dissolved in a liquid such as blood. Mental, emotional, or nervous strain.

Outer core

The 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.

Mantle

The region of the interior of the Earth between the core and the crust

Asthenosphere

The upper part of the Earth's mantle, extending from a depth of about 75 km

Plate tectonics

a theory in geology: the lithosphere of the earth is divided into a small number of plates which float on and travel independently over the mantle and much of the earth's seismic activity occurs at the boundaries of these plates.

Strike-slip fault

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.

Mesosphere

the part of the earth's atmosphere between the stratosphere and the thermosphere in which temperature decreases with altitude to the atmosphere's absolute minimum.

Crust

the thin and solid outermost layer of the Earth above the mantle

Tectonic plate

the two sub-layers of the earth's crust (lithosphere) that move, float, and sometimes fracture and whose interaction causes continental drift, earthquakes, volcanoes, mountains, and oceanic trenches.