Geology: Solar System & Earth Formation

Big Bang

The theory that the Universe started with a expansive explosion. Shortly after, elements were created and galaxies started to form.

Solar nebular hypothesis

The idea that a nebula can collapse and form a star with planets.

Giant Impact hypothesis

Idea that a large body struck the Earth, sprayed material into space, and that material eventually collected to form the Moon.

Planetary accretion

The process in which solids accumulate to form larger and larger objects, eventually forming planets.

Chemical differentiation

The process of separating out different constituents of a planetary body as a consequence of their physical or chemical behavior, where the body develops into compositionally distinct layers.

Inner core

The innermost physical layer of the Earth, which is solid.

Outer core

The outer physical layer of the core, which is liquid. Movement within the outer core is believed to be responsible for Earth's magnetic field.

Mantle

The layer of hot, solid material between Earth's crust and core.

Oceanic crust

The thin, outer layer of the Earth which makes up the rocky bottom of the ocean basins. It is made of rocks similar to basalt, and as it cools, even become more dense than the upper mantle below.

Continental crust

The layers of igneous, sedimentary, and metamorphic rocks that form the continents. Continental crust is much thicker than oceanic crust and much less dense. Its average composition is similar to granite.

Hydrosphere

The water part of the Earth, as a solid, liquid, or gas.

Atmosphere

The gases that are part of the Earth, which are mainly nitrogen and oxygen.

Biosphere

The living things that inhabit the Earth.

Geosphere

The rocky parts of the Earth, including the crust, mantle, and core.

Convection

The property of unevenly-heated (heated from one direction) fluids (like water, air, ductile solids) in which warmer, less dense parts within the fluid rise while cooler, denser parts sink. This typically creates convection cells: round loops of rising and sinking material.