Plate tectonics, rocks and weathering

Plate tectonics

The theory that explains the movement of the Earth's lithosphere which is divided into tectonic plates.

Lithosphere

The rigid outer layer of Earth, consisting of the crust and upper mantle.

Asthenosphere

The semi-fluid layer beneath the lithosphere allowing tectonic plates to move.

Oceanic plates

Tectonic plates that are young, thin, dense, and primarily composed of basalt.

Continental plates

Tectonic plates that are older, thicker, less dense, and mainly consist of granite.

Ridge push

A tectonic process where magma rises to push tectonic plates apart, as seen at mid-ocean ridges.

Slab pull

The process by which a subducted oceanic plate pulls the rest of the plate down with it due to its density.

Convection currents

Movements within the mantle caused by the heat from the Earth's interior that drive plate tectonics.

Continental drift

The theory that continents have moved slowly to their current locations over geological time.

Pangaea

The name of the supercontinent that existed during the late Paleozoic and early Mesozoic eras.

Orogenic belts

Mountain ranges formed at tectonic plate boundaries through processes like subduction.

Palaeomagnetism

The study of the Earth's magnetic field in rocks to infer the historical positions of continents.

Convergent boundary

A tectonic plate boundary where two plates collide, leading to subduction or mountain formation.

Oceanic trench

A deep trench formed at a convergent boundary where an oceanic plate is being subducted.

Magma chamber

A reservoir underground where molten rock accumulates before it erupts to the surface.

Accretionary wedge/prism

Sedimentary material that accumulates at the edge of a tectonic plate due to subduction.

Volcanic island arcs

Islands formed from volcanic activity at oceanic-oceanic convergent plate boundaries.

Mid-Atlantic Ridge

A divergent tectonic plate boundary located along the floor of the Atlantic Ocean.

Transform boundary

A tectonic plate boundary where two plates slide past each other without significant vertical movement.

San Andreas Fault

A well-known transform boundary located in California, known for its seismic activity.

Landslide

A mass movement of earth material down a slope, often triggered by rainfall or earthquakes.

Hydrolysis

A chemical weathering process where water reacts with minerals to break them down.

Carbonation

A chemical weathering process where carbon dioxide dissolves in water to form carbonic acid.

Weathering

The process of breaking down rocks in situ, while erosion involves the movement of material.

Creep

The slow, continuous movement of soil or rock down a slope due to gravity.

Solifluction

The slow, downhill flow of waterlogged soil, common in permafrost areas.

Heave

The upward movement of soil or rock due to freeze-thaw cycles.

Sheetwash

Surface runoff that moves across the soil, removing topsoil and affecting slope stability.

Geotechnical Engineering Office (GEO)

The Hong Kong governmental body responsible for assessing and managing slope safety.

Chelaion

The process of breaking down material due to the release of organic acids from vegetation.