Rocks and Weathering Practice Flashcards

A set of vocabulary flashcards covering plate tectonics, physical and chemical weathering processes, and mass movements based on the lecture materials.

Lithosphere

The upper surface layer of the Earth, including the crust and the upper mantle, which is about $70\,km$ deep.

Continental crust

A layer of the Earth’s crust that is $35\text{--}70\,km$ thick on average, very old, and primarily granitic in nature.

Oceanic crust

A layer of the Earth’s crust that is $6\text{--}10\,km$ thick on average, very young, and primarily basaltic in nature.

Convection current theory

A theory stating that huge currents occur in the Earth's interior where magma rises due to radioactive decay and spreads at mid-ocean ridges.

Hotspot

A plume of lava that rises vertically through the mantle, such as the Hawaiian hotspot, which may create a drag force causing plate movement.

Paleomagnetism

The phenomenon where magnetic grains in cooling lava acquire the direction of the Earth's magnetic field at the time of cooling.

Sea-floor spreading

A process occurring at constructive margins where ocean floors grow and new oceanic crust is created as plates move apart.

Subduction

The process where one plate is forced downwards into the mantle at a convergent boundary, often forming deep-sea trenches.

Transform fault

A fault zone created where plates slide past one another without colliding or separating, often associated with shallow earthquakes.

Ocean ridges

Giant submarine mountain chains with a total length of more than $60,000\,km$ that rise $2\text{--}3\,km$ above the surrounding ocean basins.

Island arcs

A volcanic island chain formed in an arc-shape when oceanic lithosphere is subducted beneath other oceanic lithosphere.

Weathering

The decomposition and disintegration of rocks in situ.

Freeze–thaw

A physical weathering process where water in cracks freezes at $0^{\circ}C$, expanding by about $10\%$ and exerting pressure up to $2100\,kg/cm^2$.

Exfoliation

A physical weathering process in hot deserts where the outer layers of rock peel due to stresses from a large diurnal temperature range.

Salt crystallisation

The decomposition of rock by salt solutions, where substances like $Na_2SO_4$ and $Na_2CO_3$ expand by about $300\%$ between $26\text{--}28^{\circ}C$.

Pressure release

The process whereby underlying rocks expand and fracture parallel to the surface after overlying rocks or weight are removed by erosion.

Hydrolysis

A chemical weathering process where minerals like orthoclase feldspar in granite react with acidic water to form kaolin or china clay.

Hydration

A process where certain minerals absorb water and expand, such as when anhydrite is changed into gypsum.

Carbonation–solution

A chemical process where weak carbonic acid formed from rainfall and $CO_2$ reacts with calcium carbonate to form soluble calcium bicarbonate.

Oxidation

A chemical reaction where iron compounds react with oxygen to produce a reddish brown coating, changing $FeO$ to $Fe_2O_3$.

Chelation

The process in which plant roots absorb relatively insoluble minerals by exchanging hydrogen ions with cations in adjacent minerals.

Van’t Hoff’s law

The principle stating that the rate of chemical weathering increases $2\text{--}3$ times for every $10^{\circ}C$ increase in temperature.

Tor

An isolated mass of bare rock, often granite, left standing on a hilltop after the surrounding rock has been broken down and removed.

Equifinality

A concept in geomorphology stating that different processes can produce the same end result.

Swallow holes

Depressions or sinks in the ocean floor or limestone surfaces, ranging from small-scale to large dolines up to $30\,m$ in diameter.

Regolith

The superficial and unconsolidated material found at the Earth’s surface, including soil, scree, and weathered bedrock.

Mass movements

Large-scale movements of the Earth’s surface that are not accompanied by a moving agent such as a river, glacier or ocean wave.

Shear strength

The internal resistance of a slope to mass movement.

Shear stress

The forces attempting to pull a mass downslope.

Tailings

The impurities left behind after a mineral has been extracted from its ore during the mining process.