Earth's Systems

geosphereThe system made of all of Earth's rock and metal, from the ground under your feet to the center of the planet. It includes the crust, the mantle and the core.Chapter 10

hydrosphereThe system made of all of Earth's water in every form: oceans, lakes, rivers, groundwater, ice sheets, cloud droplets and invisible water vapor.Chapter 10

atmosphereThe layer of gases that gravity holds around Earth, mostly nitrogen and oxygen. It thins out gradually with height instead of ending at a sharp edge.Chapter 10

biosphereThe system made of every living thing on Earth plus all the places in rock, water and air where life can survive.Chapter 10

crustThe outermost layer of the geosphere: a cool, brittle shell of rock that is thin next to the layers below it and the least dense. Continental crust averages about 35 km thick; ocean crust is thinner, around 7 km.Chapter 10

mantleThe thick layer of hot rock between the crust and the core. It is solid, yet over millions of years it creeps and circulates like an extremely stiff putty.Chapter 10

coreEarth's center, made mostly of the metals iron and nickel. The outer core is liquid; the inner core is solid because of the enormous pressure. It is the densest and hottest layer.Chapter 10

densityThe amount of mass packed into a given volume, such as grams per cubic centimeter. Warming a material usually spreads its particles out and lowers its density.Chapter 10

conductionEnergy passing from particle to particle through a material, or between materials that touch, always from the warmer side to the cooler side, without the material itself moving.Chapter 10

convectionEnergy carried along by moving matter: warmer, less dense material is pushed upward as cooler, denser material sinks under gravity, forming a loop called a convection cell.Chapter 10

radiationEnergy traveling as light, including invisible infrared light. Radiation needs no matter to carry it, so it can cross the empty space between the Sun and Earth.Chapter 10

closed systemA system that matter cannot enter or leave. Energy, such as sunlight and heat, can still cross the boundary.Chapter 10

weatheringThe breaking down of rock where it sits, either into smaller pieces by physical forces (frost, grinding, roots) or into new substances by chemical reactions. Weathering loosens rock; it does not carry it away.Chapter 11

erosionThe picking up and moving of loosened rock material by flowing water, wind, moving ice or gravity.Chapter 11

depositionThe settling and piling up of carried rock material in a new place when the water, wind or ice that moved it slows down or stops.Chapter 11

upliftThe raising of a large area of Earth's crust by forces from deep inside the planet. Uplift is usually very slow, but during a large earthquake a patch of land can rise several meters in minutes.Chapter 11

uniformitarianismThe principle that the kinds of natural processes we can observe today, following the same natural laws, also operated in the past and will operate in the future. It does not claim that every process always ran at the same speed, and it leaves room for sudden events.Chapter 11

spatial scaleThe size range of the thing or change you are describing, from microscopic (too small to see) through human-sized to regional and global (the whole planet).Chapter 11

time scaleThe range of durations you are describing, from fractions of a second through years and centuries to millions and billions of years.Chapter 11

rate of changeHow much something changes divided by how long the change took, such as millimeters per year or centimeters per century. Rates let scientists compare slow and fast processes with numbers.Chapter 11

catastrophic eventA sudden, powerful event such as a landslide, flash flood, volcanic eruption or asteroid impact that reshapes part of Earth's surface in seconds to weeks. The conditions that make it possible usually build up over a much longer time.Chapter 11

chemical weatheringWeathering in which a chemical reaction changes or dissolves rock. Rainwater holding a little dissolved carbon dioxide is weakly acidic, and over long spans it dissolves limestone to open caves.Chapter 11

compaction and cementationTwo steps that turn loose sediment into rock: the weight of layers above squeezes the grains together (compaction), and minerals left behind by groundwater glue the grains to one another (cementation).Chapter 11

hoodooA tall, thin pillar of rock, usually with a cap of tougher rock on top, left standing while weathering and erosion strip away the softer rock around it.Chapter 11