HiSet Earth and Space Science A: Earth

Terms from the Earth section

Atmosphere

The layer of gases surrounding Earth, essential for weather, climate, and supporting life.

Axis

An imaginary line around which Earth rotates, tilted at about 23.5 degrees.

Continental Drift

The theory that Earth's continents have moved over geological time to their current locations.

Core

The innermost layer of Earth, composed mostly of iron and nickel, with a solid inner core and liquid outer core.

Crust

The thin, outermost layer of Earth where we live, composed of solid rock.

Exosphere

The outermost layer of Earth's atmosphere, where atmospheric gases gradually fade into space.

Fault Lines

Cracks in Earth's crust along which movement occurs, often causing earthquakes.

Geologic Time

The timeline used to describe Earth’s 4.6-billion-year history, divided into eons, eras, periods, and epochs.

Glaciers

Large, slow-moving masses of ice formed from compacted layers of snow.

Global Warming

The long-term increase in Earth's average surface temperature due to human activities and greenhouse gas emissions.

Greenhouse Effect

The trapping of heat in Earth’s atmosphere by gases like carbon dioxide and methane.

Hydrosphere

All of Earth’s water, including oceans, lakes, rivers, glaciers, and water vapor in the atmosphere.

Igneous Rocks

Rocks formed from cooled and solidified magma or lava.

Ionosphere

A layer of the atmosphere containing ions, important for radio communication, located within the thermosph-ere.

Magma

Molten rock located beneath Earth’s surface.

Mantle

The thick middle layer of Earth made of semi-solid rock that flows slowly.

Mesosphere

The layer of the atmosphere above the stratosphere, where temperatures drop and meteors burn up.

Metamorphic Rocks

Rocks formed when existing rocks are changed by heat and pressure.

Minerals

Naturally occurring, inorganic solids with a specific chemical composition and crystal structure.

Ozone

A gas made of three oxygen atoms; in the stratosphere, it protects life by absorbing harmful UV radiation.

Pangaea

A supercontinent that existed about 300 million years ago before breaking apart into today’s continents.

Plate Tectonics

The theory explaining the movement of Earth’s plates that shapes the planet's surface.

Revolution

The movement of Earth around the Sun, taking about 365.25 days to complete.

Rotation

The spinning of Earth on its axis, causing day and night, completed once every 24 hours.

Sedimentary Rocks

Rocks formed from the accumulation and compaction of sediments.

Stratosphere

The second layer of Earth’s atmosphere, where the ozone layer is located.

Subduction

The process where one tectonic plate sinks beneath another into the mantle.

Thermosphere

A high-temperature layer of the atmosphere above the mesosphere, where auroras occur.

Trench

A deep depression in the ocean floor, typically formed by subduction zones.

Troposphere

The lowest layer of Earth’s atmosphere, where weather occurs and most air molecules are found.

Volcanoes

Openings in Earth’s crust where magma, gases, and ash erupt.

Water Cycle

The continuous movement of water on, above, and below the surface of Earth through processes like evaporation, condensation, and precipitation.