Astronomy and Earth Science Key Vocabulary

A comprehensive set of vocabulary flashcards covering key astronomy and geology concepts—from celestial models and planetary formation to Earth systems, rock types, and surface processes.

Geocentric Model

Claudius Ptolemy which states that earth is at the center of the solar system

Heliocentric Model

Nicholas Copernicus developed a model explaining the structure of the solar system

Angular Momentum

The quantity of rotation of a body, which is the product of its movement of inertia and its angular velocity

Nebular Hypothesis

Immanuel Kant and Pierre-Simon Laplace propose the earliest theory of how the solar system was originated

Nebula

cloud of dispered interstellar gas and dust where new stars can form.

Orion Nebula

One of the brightest nebulae

Planetesimal and Tidal Theories

Thomas Chowder Chamberlain and Forest Ray Moulton proposed that a star passed close enough to the sun, creating huge tides and causing materials to be ejected

Jeans–Jeffreys Tidal Theory

variation of the planetesimal concept. suggested that when a huge tidal wave was created from sun’s collision with another star, a long filament was drawn out

Protoplanet Theory

Modified version of nebular hypothesis. Under the influence of turbulence and tidal action

Habitable Zone

Earth’s distance from the sun, allows earth to hold water in its liquid form

Greenhouse Effect

Just one of the many benefits of having an atmosphere

Axis

Imaginary line through a rotating body; Earth’s axis runs from the North to the South Pole.

23.5° (Earth’s Axial Tilt)

Earth’s Axis is tilted at

Sidereal Day

The amount it takes for earth to turn on its axis. 23hrs

Solar Day

The amount of time it takes for the sun to return to the same spot (~24 h).

Biologically

Only photosynthetic organisms are capable of harnessing and converting radian energy into chemical

Physiologically

All organisms respond to stimulus

Melanin

A brown to black pigment occuring in the hair, skin, and the iris of the eyes and animals

Meteorology

Earth’s weather and climate is driven by solar radiation

Season

Changes in weather, ecology and daytime

Spring, Summer, Fall, Winter

Seasonal Variations

Subsystems

Earth Science look at the entire planet as a system of interacting parts

Regolith

loose particles of rocks

Geosphere, Hydrosphere, Atmosphere, Biosphere

Four basic subsystem

Geosphere

Composed of naturally occuring solid aggregate of minerals, organic materials, or natural glass and loose particles of rocks

Hydrosphere

Totality of Earth’s water

Cryosphere

permanently frozen parts

Atmosphere

Mixtures of gases that surround the planet

Biosphere

Includes all life forms, even organic that has not yet decomposed

Lithosphere

outermost layer which is composed of the crush and the upper mantle

Rock

Naturally occurring solid aggregate of minerals or mineraloids.

Rock Cycle

Continuous processes that transform rocks among igneous, sedimentary, and metamorphic forms.

Igneous Rocks

Rocks formed from the solidification of magma or lava.

Ignis

Latin word for “fire,” root of the term igneous.

Sedimentary Rocks

Accumulate on earth’s surface

Deposition

Accumulate on earth’s surface in a process

Metamorphic Rocks

Rocks altered by heat, pressure, or chemically active fluids without melting.

Protolith

Original rock from which a metamorphic rock forms.

Texture (Geology)

Size, shape, and arrangement of mineral grains within a rock.

Aphanitic

rocks have grains that are too small to see or identify

Phaneritic

minerals that are commonly found in the earth’s crust and are responsible for the formation of various types of rocks

Rock-Forming Minerals

composed of elements such as those found in the periodic table

Minerals

Naturally occurring, inorganic solids with a definite chemical composition and crystalline structure.

Luster

Color of a freshly broken surface of mineral

Color (Mineralogy)

Finely formed powder

Streak

resistance to abrasian

Hardness

Mineral’s resistance to scratching, measured by the Mohs scale.

Cleavage

Tendency of a mineral to break along flat, parallel planes of weakness.

Fracture

Irregular breakage of a mineral that does not follow cleavage planes.

Specific Gravity

Relative density of a mineral compared with water; indicates heft.

Abraham Gottlob Werner

18th-century German geologist and mineralogist; pioneer of mineral classification and Neptunism.

Weathering

Breakdown of rocks at Earth’s surface by physical, chemical, and biological processes.

Physical Weathering

Mechanical fragmentation of rocks without chemical alteration.

Exfoliation

Physical weathering where outer rock layers peel away due to pressure release or temperature change.

Frost Action

Alternate freezing and thawing of water in cracks and pores of rocks

Frost Wedging

When Ice forms in cracks, expands, and breaks up rocks

Subsystem (Earth System)

One component of Earth’s interacting spheres—geosphere, hydrosphere, atmosphere, cryosphere, or biosphere.

Chemical Weathering

Decomposition of rocks through chemical reactions that change mineral composition.

Biotic Weathering

Rock breakdown by living organisms such as plant roots, lichens, or microbes.

Geosphere

Solid portion of Earth, including rocks, minerals, and landforms.

Hydrosphere

All liquid water on Earth—oceans, lakes, rivers, and groundwater.

Atmosphere

Layer of gases surrounding Earth, essential for climate and life.

Cryosphere

Frozen water part of Earth—glaciers, sea ice, ice caps, and permafrost.

Biosphere

All ecosystems and living organisms on Earth.

Mass Wasting

Downslope movement of soil and rock under the influence of gravity.

Regolith

Loose, heterogeneous layer of soil, dust, and broken rock covering solid bedrock.