Earth's Structure and Composition

Flashcards covering the interior structure, concentric layers, discontinuities, chemical compositions, and geological theories of the Earth based on lecture notes.

Primary Waves (P-waves)

Earthquake seismic waves that reach the surface of the earth and decrease in velocity at the Gutenberg Discontinuity.

Secondary Waves (S-waves)

Seismic waves that do not pass through liquids and disappear completely in the outer core and at the Gutenberg Discontinuity.

Magma Chamber

A reservoir deep inside the earth from which molten material rises to the surface during volcanic eruptions.

Meteorites

Rocks falling from outer space that scientists study because the earth is constituted of the same materials.

Lithosphere

The outer layer or outermost crust of the earth made of solid rocks (from Lithos meaning stones or rocks) containing large contents of silicates, feldspar, and mica.

Hydrosphere

The parts of the earth's crust that are immersed under the oceans and seas.

Atmosphere

The blanket of gases that extends upwards and envelopes the earth.

SIAL

The continental layer of the earth's crust, named after Silica (Si) and Aluminium (Al), which has less density and floats above Sima.

SIMA

The oceanic floor layer of the earth's crust, named after Silica (Si) and Magnesium (Mg).

NIFE

The core of the earth, named after its primary high-density heavy metals Nickle (Ni) and Iron (Fe).

Core

The most inaccessible and densest part lying at the centre of the earth, measuring about $7000\,\text{km}$ in diameter with temperatures ranging from about $4400^\circ\text{C}$ to about $6000^\circ\text{C}$.

Earth's Magnetism

The magnetic field oriented towards the North and South Poles, generated by the iron and nickel composition of the core.

Mantle

The layer lying below the crust with an average thickness of $2900\,\text{km}$ that makes up $84\%$ of the earth's total volume.

Upper Mantle

The cooler section of the mantle made of solid rocks that extends from the Moho Discontinuity to a depth of $700\,\text{km}$.

Lower Mantle

The hotter and denser section of the mantle extending from $700\,\text{km}$ to $2900\,\text{km}$, which is solid due to high pressure.

Asthenosphere

A partially molten layer of the mantle located at a depth of around $100\text{--}410\,\text{km}$.

Gutenberg Discontinuity

The boundary or interface between the mantle and the core that begins at a depth of $2800\,\text{km}$, marked by an abrupt change in seismic waves.

Mohorovicic Discontinuity (Moho Discontinuity)

The boundary between the crust and mantle discovered in 1909 by Andreaja Mohorovic, found at about $8\,\text{km}$ beneath oceans and $32\,\text{km}$ beneath continents.

Theory of Continental Drift

A theory put forward by Wegener in the early 20th century suggesting that the earth's crust undergoes structural changes.

Theory of Plate Tectonics

A theory put forth in the 1960s explaining structural changes and lateral movements of the earth's crust over millions of years.