13: Key Terms

CHAPTER 2

asthenosphere - the semi-fluid layer of the mantle beneath the lithosphere that allows tectonic plates to move

biochemical sedimentary rock - rock formed as shells made of precipitated mineral material collect and cement together

chemical sedimentary rock - rock formed as minerals precipitate from solution

clastic sedimentary rock - rock formed from the accumulation, compression and cementation of sediments

cleavage - the way a mineral naturally breaks along specific planes of weakness in its crystal structure, forming smooth, flat surfaces

convergent boundary - boundary between two tectonic plates at which the two plates move toward one another

core - the central part of Earth, consisting of a solid inner layer and a liquid outer layer, made mostly of iron and nickel

crust - the thin, outermost layer of Earth, made up of solid rock

decompression melting - the process by which rocks melt due to a decrease in pressure, typically occurring at mid-ocean ridges or hot spots

divergent boundary - boundary between two tectonic plates at which the two plates move away from one another

earthquakes - the shaking of the Earth's surface caused by the release of energy along fault lines or from volcanic activity

extrusive rock - an igneous rock that forms from lava cooling quickly at or near the Earth's surface

felsic - a type of igneous rock rich in silica and light-colored minerals

foliated - characteristic of a metamorphic rock by which it has a fabric of aligned minerals or aligned bands of minerals

hardness - a measure of how resistant a mineral is to being scratched

igneous rock - rock formed as molten material cools

intermediate - a type of igneous rock with a composition between felsic and mafic, often lighter than mafic rocks but darker than felsic rocks

intrusive rock - an igneous rock that forms from magma cooling slowly beneath the Earth's surface

lava - molten rock on the surface

lithosphere - the rigid outer layer of Earth, made up of the crust and the uppermost part of the mantle, broken into tectonic plates

mafic - a type of igneous rock that is rich in magnesium and iron and darker in color

magma - molten rock below the surface

mantle - the thick, middle layer of Earth's interior, located below the crust and above the core, made of a mix of solid and semi-solid rock

mass wasting - the failure and down-slope movement of rock or unconsolidated materials in response to gravity

metamorphic rock - rock that has been changed from its original form by heat, pressure, or chemical processes

mineral - a naturally occurring, inorganic solid with a specific chemical composition and crystal structure

organic sedimentary rock - rock formed through the accumulation of organic material

plate - a rigid piece of Earth's lithosphere that moves on top of the asthenosphere.

plate boundary - the area where two tectonic plates meet

rock cycle - the continuous process by which rocks are formed, altered, destroyed, and reformed through geological processes like melting, cooling, erosion, and exposure to pressure

rocks - aggregates of the crystals of one or more minerals

sedimentary rock - rock formed from the accumulation and compression of sediments, through the accumulation of precipitated minerals, or through the accumulation of organic material

silica tetrahedron - a basic building block of silicate minerals, consisting of one silicon atom bonded to four oxygen atoms in a pyramid shape

silicate minerals - minerals that contain silicon and oxygen as their main elements, forming the majority of Earth's crust

specific gravity - the ratio of a mineral's density compared to the density of water

transform boundary - boundary between two tectonic plates at which the two plates slide past one another

volcanic rock - a type of igneous rock formed from lava that cools and solidifies quickly on or near Earth's surface

CHAPTER 3

chemical weathering - the chemical change of earth material into materials with a different composition resulting from exposure to the atmosphere

clay - any unconsolidated material with a grain diameter less than 0.004 mm, or the group of minerals called clay minerals, which are sheet silicates

exfoliation - the process by which layers or sheets of rock peel off due to changes in temperature or pressure

frost wedging - the process by which the water seeps into cracks in a rock, expands on freezing, and thus enlarges the cracks

hydrolysis - a chemical weathering process where minerals in rock react with water, causing them to break down and form new minerals, usually clay

mechanical weathering - the physical breakdown of rock into smaller pieces

oxidation - a chemical weathering process where minerals, especially those containing iron, react with oxygen in the air or water, causing them to lose electrons and become weaker

parent material - the material from which a soil forms

relief - the slope of a surface

soil - loose material formed in place by weathering the underlying materials

soil horizon - a distinct layer of soil that differs in color, texture, and composition from the layers above or below it

weathering - the process by which rock breaks down

CHAPTER 4

cinder cone - a small, steep-sided volcano made of ash, cinders, and other volcanic debris that erupts explosively and is usually made of mafic materials

composite volcano - a large, steep-sided volcano formed by alternating eruptions of lava flows and explosive ash, creating layers of solidified lava and debris

lahar - volcanic mudflow or debris flow

shield volcano - a broad, gently sloping volcano formed by the eruption of low-viscosity, mafic lava that flows easily, creating wide, shield-like shapes

tephra - volcanic rock fragments of any size such as the very small volcanic ash

volatiles — components that behave as gases during volcanic eruptions

CHAPTER 5

body waves - seismic waves that travel through the Earth's interior, including P-waves (primary waves) and S-waves (secondary waves), during an earthquake

earthquake intensity - a measure of what people felt and how much damage was done during an earthquake

earthquake magnitude - a measure of the amount of energy released during an earthquake

elastic deformation - he temporary change in shape or size of rocks due to stress, which can return to its original form once the stress is removed

epicenter - the point on the land surface directly above the hypocenter of the earthquake

hypocenter - the actual location of an individual earthquake's starting point at depth in the ground

intraplate - being located away from a plate boundary in the more center part of the plate

liquefaction - process by which otherwise solid body of sediment gets transformed into a liquid mass that can flow, often as a result of an earthquake

stress - force applied to a body

strain - change in shape caused by stress

surface waves - seismic waves that travel along the Earth's surface, causing most of the shaking felt during an earthquake; they include Love waves and Rayleigh waves

tsunami - very large wave, usually in the ocean, generated as the seafloor moves as a result of an earthquake event

CHAPTER 6

creep - very slow movement of soil or other unconsolidated material on a slope

debris flow - the down slope movement of a mix of different size materials that occurs when a mass of sediment becomes completely saturated with water, to the extent that the mass loses strength and flows

mud flow - the down slope movement of mud-sized materials that occurs when a mass of sediment becomes completely saturated with water, to the extent that the mass loses strength and flows

rock avalanche - the sliding motion of rock along a sloping surface at very fast rates

rock fall - abrupt movement of rock which become detached from steep slopes or cliffs

rock slide - the sliding motion of rock along a sloping surface

slump - a type of slide that takes place within thick unconsolidated deposits where there is movement along a curved surface such that there is downward motion near to the top and outward motion towards the bottom

CHAPTER 7

ammonification - the process by which decomposers break down organic matter (like dead plants and animals) and release nitrogen in the form of ammonia

carbon cycle - the process by which carbon is exchanged between the atmosphere, oceans, soil, plants, and animals, helping regulate Earth's climate

climate - the average weather for a region over time

denitrification - the process by which bacteria convert nitrates back into nitrogen gas, returning it to the atmosphere

exosphere - the outermost layer of Earth's atmosphere, where particles are very spread out and can escape into space

mesosphere - the middle layer of Earth's atmosphere, where meteors burn up upon entering

nitrification - the process by which certain bacteria convert ammonia into nitrites and then into nitrates, which plants can use as a nutrient

nitrogen cycle - the process by which nitrogen moves between the atmosphere, soil, plants, and animals, involving various bacteria and other organisms

nitrogen fixation - the process by which certain bacteria convert nitrogen gas from the atmosphere into forms (like ammonia) that plants can use for growth

photosynthesis - the process by which plants use sunlight, carbon dioxide, and water to produce food (glucose) and oxygen

stratosphere - the layer above the troposphere, where the ozone layer is located and where weather is more stable

thermosphere - a layer of the atmosphere above the mesosphere, where temperatures increase with altitude and where the auroras occur

troposphere - the lowest layer of Earth's atmosphere, where weather happens and clouds form

weather - the summation of current atmospheric conditions at any given moment

CHAPTER 8

aquifer - a layer of rock or sediment that stores and transmits groundwater, often used as a source of potable water

aquitard - a layer of rock or sediment that slows or prevents the flow of groundwater, acting as a barrier between aquifers

cone of depression - a funnel-shaped depression in the water table that forms around a well when groundwater is being pumped out faster than it can be replenished

confined aquifer - an aquifer that is trapped between two layers of impermeable rock or sediment, preventing easy flow of water

drainage basin - the area of land where all water drains into a single river or stream, including its tributaries

drainage divide - high spot that separates two drainage basins

drought - a period of reduced rainfall and/or snowfall that results in water-related problems

floodplain - the flat area of land next to a stream that is prone to flooding during heavy rain or when the river overflows

flood recurrence interval - the probability that a flood of a certain size will happen at some time in the future

groundwater - the water stored in the open spaces within unconsolidated sediment and the underlying bedrock

overland flow - the movement of water across the land's surface, usually after heavy rainfall, before it reaches streams

permeability - the interconnectedness of the pores in a rock or sediment which determines how well fluid can flow through the body

porosity - the amount of open pore space in a rock or sediment

saturated zone - the layer of rock or sediment where all the pore spaces are filled with water, located below the water table

stream - a body of flowing surface water of any size

subsidence - the lowering of the Earth's surface due to the removal of groundwater

transpiration - evaporation by solar energy from plants

tributary - a smaller stream that feeds into the larger one

turbidity - a measure of the amount of solid matter suspended in water

unconfined aquifer - an aquifer that is not sealed by an impermeable layer and is open to the surface, allowing water to easily flow in and out

unsaturated zone - the layer of rock or sediment above the water table, where pore spaces contain both air and water

water table - the upper limit of the saturated zone

CHAPTER 9

fossil fuels - natural fuels like coal, oil, and natural gas formed from the remains of ancient plants and animals, used to produce energy

geothermal energy - energy derived from the heat stored inside the Earth, often used for heating or generating electricity

hydroelectric power - energy produced by the movement of water, typically from dams or flowing rivers, to generate electricity

non-renewable sources - energy sources that once they are extracted from Earth materials and consumed, they are gone

nuclear energy - the energy that is stored in the nuclei of atoms

nuclear fission - a process in which the nucleus of an atom splits into smaller parts, releasing a large amount of energy

nuclear fusion - a process where two atomic nuclei combine to form a heavier nucleus, releasing energy; this is the process that powers the Sun

solar energy - energy harnessed from the Sun, typically using solar panels or solar collectors

tides - the regular rise and fall of sea levels caused by the gravitational pull of the Moon and Sun on Earth’s oceans

wind energy - energy generated by the movement of air, typically captured using wind turbines

CHAPTER 10

dump - a place where waste is discarded

landfill - an engineered structure with barriers to contain the waste, mechanisms to capture and treat liquid and gaseous waste byproducts, and procedures in place to monitor the surrounding water and air

monitoring wells - wells constructed around a landfill to sample the groundwater and determine if any contaminants are escaping

CHAPTER 11

greenhouse gases - gases that trap the Earth’s heat in the atmosphere, leading to warmer temperatures

nonpoint sources - pollution that comes from multiple, scattered sources, such as runoff from roads or farmland, rather than a single identifiable location

point sources - pollution that comes from a single, specific location, such as a factory or wastewater treatment plant

underground storage tanks

smog - a type of air pollution made up of smoke, fog, and chemical pollutants, often caused by vehicle emissions and industrial activity

soot - Fine black particles produced by burning fossil fuels or wood, which pollute the air

CHAPTER 12

glacial - a period of cooler climate often referred to as an ice age when glaciers are advancing/growing

interglacial - a period of warmer climate between glacials, when glaciers are retreating/melting

permafrost - ground that remains frozen year-round