Earth Science: Science Terms Explained
Plain-language definitions of every earth science term your child meets in school, each with kid-friendly explanations, worked examples, and common mistakes to watch for.
Canyon
A canyon is a deep, narrow valley with steep sides, usually carved into rock over a long time by a river or stream cutting downward as it flows.
Cave
A cave is a natural underground space large enough for a person to enter, usually formed when rock is worn away by water, waves, lava, or other natural processes.
Continental drift
Continental drift is the idea that Earth's continents have slowly moved across the planet's surface over hundreds of millions of years, changing position and shape over time.
Crust
The crust is Earth's thin, solid outer layer made of rock, where all continents, oceans, and living things are found, and it sits on top of the hotter, softer mantle below.
Delta
A delta is a landform made of sediment that builds up where a river slows down and meets a larger body of water, such as an ocean, sea, or lake, often creating a wide, fan-shaped area of new land.
Deposition
Deposition is the process in which wind, water, ice, or gravity drops and leaves behind sediment, building up new layers of rock and landforms over time.
Earthquake
An earthquake is a sudden shaking of the ground that happens when rocks inside Earth move and break, releasing stored energy as seismic waves that travel through the Earth.
Erosion
Erosion is the process where wind, water, ice, or gravity pick up and move rock, soil, or sand from one place to another, slowly changing the shape of Earth's surface over time.
Fault
A fault is a crack or break in Earth's crust where rocks on one side have moved past rocks on the other side.
Fossil
A fossil is the preserved remains, trace, or imprint of a once-living organism, such as a plant or animal, that lived long ago and became trapped and preserved in rock or other materials over time.
Geologic time
Geologic time is the way scientists describe Earth’s entire history, from its formation about 4.6 billion years ago to today, using a special timeline divided into very large units like eons, eras, and periods.
Glacier
A glacier is a large, long-lasting mass of ice that forms on land from compacted snow and slowly moves under its own weight, shaping the landscape by eroding and depositing rock and sediment.
Igneous rock
Igneous rock is rock that forms when hot, melted rock material such as magma or lava cools and hardens, either deep underground or at Earth’s surface.
Landform
A landform is a natural shape or feature on Earth's surface, such as a mountain, valley, hill, plain, or canyon, that is formed by processes like moving water, wind, ice, and shifting rock.
Landslide
A landslide is a rapid movement of rock, soil, and other earth materials down a slope, usually caused by gravity working on weakened or loosened ground.
Layers of the earth
Layers of the earth are the main parts that make up our planet from the outside in, usually described as the crust, mantle, outer core, and inner core, each with different materials, temperatures, and behaviors.
Mantle
The mantle is the thick layer of hot, mostly solid rock between Earth's thin outer crust and its central core, and its slow, flowing motion helps drive plate tectonics, volcanoes, and earthquakes.
Metamorphic rock
Metamorphic rock is rock that has been changed from an existing rock into a new type of rock by high heat, high pressure, or hot mineral-rich fluids, without completely melting.
Mineral
A mineral is a naturally occurring, solid substance made in Earth, with a definite chemical makeup and an orderly, repeating crystal structure.
Mountain
A mountain is a tall, steep landform that rises high above the land around it, usually with a noticeable peak or summit and sides that slope sharply upward.
Natural hazards
Natural hazards are dangerous events that happen in nature, such as earthquakes, floods, hurricanes, or wildfires, that can harm people, animals, and the environment.
Pangaea
Pangaea was a giant "supercontinent" that existed hundreds of millions of years ago, when almost all of Earth's land was joined together in one huge piece before breaking apart into the continents we know today.
Plate tectonics
Plate tectonics is the scientific theory that Earth’s outer shell is broken into large, moving pieces called plates, whose slow motion shapes the planet’s surface by forming mountains, causing earthquakes, and creating new ocean floor.
Relative and absolute dating
Relative and absolute dating are two ways scientists figure out the age of rocks and fossils: relative dating tells which rocks are older or younger compared with others, and absolute dating estimates a rock's actual age in years.
Rock cycle
Rock cycle is the ongoing process that forms, breaks down, and changes rocks into different types through heat, pressure, melting, cooling, and weathering on Earth.
Sand dune
A sand dune is a hill or ridge of loose sand that is piled up by the wind, usually found in deserts or along beaches, and can slowly move and change shape over time.
Sediment
Sediment is loose pieces of rock, mineral, or organic material that have been broken down by weathering and moved by wind, water, ice, or gravity, often settling in layers on the land or at the bottom of rivers, lakes, and oceans.
Sedimentary rock
Sedimentary rock is a type of rock that forms when bits of broken rock, minerals, or once-living things settle in layers, get buried, and are pressed and cemented together over time.
Seismic waves
Seismic waves are vibrations that travel through Earth when energy is suddenly released, most often during an earthquake, and they move outward from the source like ripples from a stone dropped in water.
Soil
Soil is the loose, top layer of Earth made from broken-down rock, water, air, and once-living material that supports plant life and many living things.
Tectonic plates
TECTONIC PLATES are huge, rigid pieces of Earth's outer shell that fit together like a jigsaw puzzle and slowly move over the softer rock beneath, shaping Earth's surface by forming mountains, causing earthquakes, and creating volcanoes where they meet.
Topographic map
A topographic map is a detailed map that shows the shape and height of the land using contour lines, symbols, and colors so you can see hills, valleys, and other landforms from above.
Valley
A valley is a long, low area of land between higher ground such as hills or mountains, usually formed over a long time by moving water, ice, or shifting Earth plates.
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