Unit 4: Earth Systems and Resources (Chapter 4, 8)

Core

Core

The innermost zone of Earth’s interior, composed mostly of iron and nickel. It includes a liquid outer layer and a solid inner layer.

Mantle

The layer of Earth above the core, containing magma.

Magma

Molten rock.

Asthenosphere

The layer of Earth located in the outer part of the mantle, composed of semi-molten rock.

Lithosphere

The outermost layer of Earth, including the mantle and crust.

Crust

In geology, the chemically distinct outermost layer of the lithosphere.

Hot spot

In geology, a place where molten material from Earth’s mantle reaches the lithosphere.

Plate tectonics

The theory that the lithosphere of Earth is divided into plates, most of which are in constant motion.

Tectonic cycle

The sum of the processes that build up and break down the lithosphere.

Subduction

The process of one crustal plate passing under another.

Volcano

A vent in the surface of Earth that emits ash, gases, or molten lava.

Divergent plate boundary

An area beneath the ocean where tectonic plates move away from each other.

Seafloor spreading

The formation of new ocean crust as a result of magma pushing upward and outward from Earth’s mantle to the surface.

Convergent plate boundary

An area where plates move toward one another and collide.

Transform fault boundary

An area where tectonic plates move sideways past each other.

Fault

A fracture in rock caused by a movement of Earth’s crust.

Seismic activity

The frequency and intensity of earthquakes experienced over time.

Fault zone

A large expanse of rock where a fault has occurred.

Earthquake

The sudden movement of Earth’s crust caused by a release of potential energy along a geologic fault and usually causing a vibration or trembling at Earth’s surface.

Epicenter

The exact point on the surface of Earth directly above the location where rock ruptures during an earthquake.

Richter scale

A scale that measures the largest ground movement that occurs during an earthquake.

Tsunami

A series of waves in the ocean caused by seismic activity or an undersea volcano.

Rock cycle

The geologic cycle governing the constant formation, alteration, and destruction of rock material that results from tectonics, weathering, and erosion, among other processes.

Igneous rock

Rock formed directly from magma.

Intrusive igneous rock

Igneous rock that forms when magma rises up and cools in a place underground.

Extrusive igneous rock

Rock that forms when magma cools above the surface of Earth.

Fracture

In geology, a crack that occurs in rock as it cools.

Sedimentary rock

Rock that forms when sediments such as muds, sands, or gravels are compressed by overlying sediments.

Metamorphic rock

Rock that forms when sedimentary rock, igneous rock, or other metamorphic rock is subjected to high temperature and pressure.

Physical weathering

The mechanical breakdown of rocks and minerals.

Chemical weathering

The breakdown of rocks and minerals by chemical reactions, the dissolving of chemical elements from rocks, or both.

Acid precipitation (Acid rain)

Precipitation high in sulfuric acid and nitric acid from reactions between water vapor and sulfur and nitrogen oxides in the atmosphere.

Erosion

The physical removal of rock fragments from a landscape or ecosystem.

Parent material

The underlying rock material from which the inorganic components of a soil are derived.

Soil degradation

The loss of some or all of a soil’s ability to support plant growth.

Horizon

A horizontal layer in a soil defined by distinctive physical features such as texture and color.

O horizon

The organic horizon at the surface of many soils, composed of organic detritus in various stages of decomposition.

Humus

The most fully decomposed organic matter in the lowest section of the O horizon.

A horizon (Topsoil)

Frequently the top layer soil, a zone of organic material and minerals that have been mixed together.

E horizon

A zone of leaching, or eluviation, found in some acidic soils under the O horizon or, less often, the A horizon.

B horizon

A soil horizon composed primarily of mineral material with very little organic matter.

C horizon

The least-weathered soil horizon, which always occurs beneath the B horizon and is similar to the parent material.

Cation exchange capacity (CEC)

The ability of a particular soil to adsorb and release cations.

Base saturation

The proportion of soil bases to soil acids, expressed as a percentage.

Crustal abundance

The average concentration of an element in Earth’s crust.

Ore

A concentrated accumulation of minerals from which economically valuable materials can be extracted.

Metal

An element with properties that allow it to conduct electricity and heat energy, and to perform other important functions.

Reserve

In resource management, the known quantity of a resource that can be economically recovered.

Strip mining

The removal of strips of soil and rock to expose ore.

Mine tailings

Unwanted waste material created during mining including mineral and other residues that are left behind after the desired metal or ore is removed.

Open-pit mining

A mining technique that creates a large visible pit or hole in the ground.

Mountaintop removal

A mining technique in which the entire top of a mountain is removed with explosives.

Placer mining

The process of looking for minerals, metals, and precious stones in river sediments.

Subsurface mining

Mining techniques used when the desired resources is more than 100m (328 feet) below the surface of Earth.