A measure of the amount of dissolved salt in water; average ocean salinity is 3.5%.
saltation
The intermittent movement of bed load particles.
sand dune
Sand deposit formed in regions of abundant sand and constant winds.
Santa Ana winds
Hot winds that blow east to west into Southern California in fall and winter.
satellite
An object, either natural or human made, that orbits a larger object.
savanna
The tropical wet and dry biome, typified by grasses and widely scattered deciduous trees.
scavenger
Animals that eat animals that are already dead.
scientific method
A means of investigating a testable question using empirical information gathered from experiments, experience, or observations.
sea breeze
A wind that blows from sea to land in summer when the land is warmer than the ocean.
sea level
The average height of the ocean; the midpoint between high and low tide.
sea stack
Isolated tower of rock that forms when a sea arch collapses.
seafloor spreading
The mechanism for moving continents. The formation of new seafloor at spreading ridges pushes lithospheric plates on the Earth’s surface.
seawall
Structure built parallel to the shore on the beach to protect against strong waves.
sediment
Small particle of soil or rock deposited by wind or water.
sedimentary rock
A rock that forms from the compaction of sediments or the precipitation of material from a liquid.
sedimentation
Sediments are laid down in a deposit.
seismic waves
Also called earthquake waves. Seismic waves transport the energy released during an earthquake. Seismic waves give scientists information on Earth’s interior.
seismogram
A seismogram is the printed record of seismic activity produced by a seismometer.
seismograph
An older type of seismometer in which a suspended, weighted pen wrote on a drum that moved with the ground.
seismology
The study of seismic waves including earthquakes and the Earth’s interior.
seismometer
A seismometer is a machine that measures seismic waves and other ground motions.
sewage treatment
Any process that removes contaminants from sewage or wastewater.
shadow
Darkness that occurs where a light source is blocked.
shear
Parallel stresses that move past each other in opposite directions.
shield
The part of a craton that crops out at the surface.
shield volcano
A shield-shaped volcano composed of fluid lavas.
silicates
Minerals of silicon atoms bonded to oxygen atoms.
sinkhole
Circular hole in the ground that forms as the roof of a cave collapses.
slash-and-burn
A method of clearing land for farming that involves cutting trees and then burning the leftover debris. This is common in rainforests.
slash-and-burn agriculture
Plants are slashed down and then burned to clear the land for agriculture.
slip
The distance rocks move along a fault.
slip face
Steeper, downwind side of a dune where sand grains fall down from the crest.
slump
Downslope slipping of a mass of soil or rock, generally along a curved surface.
soil
The top layer of Earth’s surface containing weathered rocks and minerals and organic material.
soil horizon
An individual layer of a complete soil profile; examples include A, B & C horizons.
soil profile
The entire set of soil layers or horizons for a particular soil.
solar eclipse
Occurs when moon passes directly between the Earth and Sun; the Moon’s shadow blocks the Sun from view.
solar flare
A violent explosion on the Sun’s surface.
solar prominence
Plasma loop flowing between sunspots.
solar system
The Sun and all the objects that revolve around the Sun as a result of gravity.
solar wind
High-speed protons and electrons that fly through the solar system from the Sun. The solar wind extends millions of kilometers out into space and can reach out into the solar system.
space probe
An unmanned spacecraft that collects data by flying near or landing on an object in space.
space shuttle
A reusable spacecraft capable of carrying large pieces of equipment or a space station.
space station
A large spacecraft in space on which humans can live for an extended period of time.
space telescope
Telescopes in orbit above Earth’s atmosphere.
species
A classification of organisms that can or do interbreed and produce fertile offspring.
specific heat
The amount of energy needed to raise the temperature of 1 gram of material by 1oC.
spectrometer
A tool that uses a prism to break light into its component colors.
spiral arm
Regions of gas and dust plus young stars that wind outward from the central area bulge.
spiral galaxy
A rotating type of galaxy with a central bulge and spiral arms with stars, gas and dust.
spit
Long, narrow bar of sand that forms as waves transport sand along shore.
spring
A point on the Earth’s surface where ground water bubbles up.
spring tide
A large tidal range that occurs when the Moon, Sun, and Earth area aligned; this happens at full and new moon phases.
squall line
A line of thunderstorms that forms at the edge of a cold front.
stalactite
Icicle-like formation of calcium carbonate from water dripping from the ceiling of a cave.
stalagmite
Deposit of calcium carbonate that grows upward in caves as water drips onto the floor.
star
A glowing sphere of gases that produces light through nuclear fusion reactions.
star cluster
A group of hundreds of thousands of stars.
star system
Small groups of stars that are close together.
stationary front
A stalled front in which the air does not move.
steppe
The biome of semi-arid deserts, with bunch grasses, scattered low bushes and sagebrush.
storm surge
Water that is pushed in a pile near shore by storm winds causing sea level to rise locally.
strain
Deformation in a rock because of a stress that exceeds the rock’s internal strength.
stratosphere
Above the troposphere; temperature increases with altitude because of the presence of ozone.
streak
The color of the powder of a mineral.
stream
A body of moving water, contained within a bank (sides) and bed (bottom).
stress
Force per unit area in a rock.
strike-slip fault
A fault in which the dip of the fault plane is vertical.
stromatolites
Reef like cyanobacteria that still exist today.
subduction
The sinking of one lithospheric plate beneath another.
subduction zone
The area where two lithospheric plates come together and one sinks beneath the other.
sublimation
The change of a substance from a solid to a gas without going through the liquid phase.
subsidence
Sinking of the land surface because of the extraction of ground water.
subsoil
The B horizon of a soil profile; beneath the topsoil.
sunspot
Cool, dark area on the Sun’s surface that have lower temperatures than surrounding areas; sunspots usually occur in pairs and come and go on an 11-year cycle.
supercontinent
A collection of continents that have come together because of the plate tectonics processes.
supercontinent cycle
The cycle in which the continents join into one supercontinent and then move apart to join together at the other side of the planet as another supercontinent.
Superfund Act
A law passed by the U.S. Congress in 1980 that held companies responsible for any hazardous chemicals that they might create.
Superfund site
A site where hazardous waste has been spilled. Under the Superfund Act, the company that created the hazardous waste is responsible for cleaning up the waste.
supernova
A tremendous explosion that occurs when the core of a star is mostly iron.
superposition
In a sequence of sedimentary rock layers, the oldest is at the bottom and the youngest is at the top.
supervolcano
A massive volcano that can produce unbelievably enormous, but rare, eruptions.
surface current
A horizontal movement of ocean water, caused by surface winds.
surface waves
Seismic waves that travel along the ground surface; they do the most damage.
suspended load
Solid particles that are carried in the main stream flow.
sustainable development
Economic development that helps people out of poverty, use resources at a rate at which they can be replaced, and protects the environment.
swamp
A low-lying wetland where water moves very slowly and oxygen levels are low.
symbiosis
Relationships between two species in which at least one species benefits.
symbiotic
A relationship between organisms in which each benefits and none is harmed.
syncline
A fold in the rocks that bends downward, in which the youngest rocks are at the center.