AS Rocks and Weathering

Acid rain

Acid rain

Rain with high pollutants, sulfur and nitrogen oxides, from factories, power stations, and car exhausts; forms corrosive rain.

Acidification

Liquids becoming acidic, dissolving rocks and minerals when containing concentrated acids like acid rain.

Asthenosphere

Upper layer of Earth's mantle, below lithosphere, with less rigid rock estimated between 85 and several hundred kilometers in depth.

Batholiths

Large areas of igneous rock formed underneath the Earth's surface by magma intruding and solidifying, typically 10-15 km deep.

Benioff zone

Area of contact between ocean and continental plates, causing earthquakes; also known as Wadati-Benioff zone.

Biological weathering

Wearing away of land by plants and animals, e.g., tree roots growing into bedrock cracks.

Carbonation

Process where carbon dioxide, often from rainwater, produces carbonic acid, dissolving rock.

Chelation

Bio-chemical weathering process where organisms produce chelates to decompose minerals and rocks by removing metallic cations.

Chemical weathering

Decomposition of rock from a chemical change due to interaction with moisture, leading to dissolved particles and clay formation.

Collisional plate boundary

Occurs when continental plates with no subduction and of equal thickness and densities collide.

Conservative plate boundary

Type of boundary characterized by two plates moving side by side, often at different rates or in different directions, creating increased stress.

Constructive plate boundary

Occurs when tectonic plates move apart, creating an upwelling of magma from beneath.

Continental crust (sial)

Relatively thick part of the crust forming large continental land masses, generally older, more complex, and less dense than oceanic crust.

Continental drift

Gradual movement of continents across the Earth's surface.

Convection currents

Heat from Earth's core carried up to the mantle via currents, moving the plates.

Convergent

In plate tectonics, plates moving towards each other, forming large mountain ranges or subduction zones.

Core

Innermost part of the Earth below the mantle, mainly composed of iron and nickel, divided into liquid outer core and solid inner core.

Crust

Outer layer of the Earth made up of tectonic plates.

Destructive plate boundary

Resulting from convergence of oceanic and continental plates or two oceanic plates, with the denser plate subducting under the less dense one.

Divergent

In plate tectonics, plates moving away from each other, creating rifts and rift valleys.

Dragging theory

Another name for slab-pull mechanism.

Exfoliation

Weathering where outer rock layers shear off due to diurnal heating and cooling, especially active in desert regions.

Fold Mountains

Mountains formed by large-scale and complex folding, e.g., the Himalayas, Andes, Alps, and Rockies.

Freeze thaw weathering

Weathering in cold climates where temperature fluctuations around freezing cause rocks with cracks or fissures to break.

Honeycomb weathering

Another name for pitting.

Hotspots

Volcanic areas fed by underlying magma, often found near tectonic plate boundaries.

Hydration

Process of rocks absorbing water into their pores and cracks.

Hydrolysis

Process where chemical bonds are broken and components partner up to form different elements, often changing the pH of a solution.

Igneous rock

Rocks formed when magma cools and solidifies.

Island arc

Line of volcanoes on islands above a subducting plate, forming an arc, e.g., the Ryukyu Islands, Japan.

Lithosphere

Hard and rigid outer surface of the solid Earth, including the crust and top of the mantle.

Magma

Hot, fluid molten rock found beneath the Earth's crust.

Mantle

Earth's layer between the crust and the core, over 2500 km thick, accounting for more than three quarters of the Earth's volume.

Mass movement

Movement of material caused by gravity, e.g., landslides and rockfalls.

Mechanical weathering

Also known as physical weathering.

Weathering

Disintegration of rock into smaller particles through mechanical processes without a change in chemical composition.

Metamorphic rock

Rocks changed by intense heat or pressure, often with increased hardness and resistance to erosion.

Mohorovicic Discontinuity (Moho)

Boundary between Earth's crust and mantle.

Mountain building

Formation of mountains on continents due to tectonic plate interaction, mainly subduction.

Oceanic crust (sima)

Relatively thin, young, and dense part of the crust under oceans.

Oceanic trenches

Deep-sea depressions along tectonic plate boundaries, often parallel to island arcs, reaching depths of 6000-11000 m.

Orogenesis

Mountain building process, from the Greek 'oros' for 'mountain' and 'genesis' for creation.

Oxidation

Rocks exposed to air due to earth movement, digging, or mass movement.

Peeling

Another term for exfoliation.

Pitting

Salt weathering creating cavities in rock surface, resembling honeycomb.

Planar landslides

Weathered rock detachment along a plane or joint, often featuring a clean and straight break.

Pressure release

Weathering due to removal of overlying materials, causing underlying rocks to expand and fracture.

Pseudo bedding planes

Structures in igneous rocks resembling bedding planes but caused by erosion due to pressure release.

Regolith

Layer of loose broken rock, soil, dust, and other materials covering solid rock.

Rockfalls

Sudden movements of rock from cliff faces caused by various factors including gravity, erosion, and weathering.

Rotational slides

Type of landslide occurring on a curved failed surface, causing the upper surface to tilt back.

Salt crystallisation

Mechanical weathering where salt particles dissolved in water expand and put pressure on the rock, causing it to break apart.

Sedimentary rocks

Rocks formed by consolidation of sediment derived from pre-existing rocks.

Sial

Silicon-rich and aluminium-rich rocks of the earth's continental upper crust.

Sima

Silicon-rich and magnesium-rich rocks of the earth's oceanic crust.

Slab-pull mechanism

Motion of a tectonic plate by subduction, causing the oldest edge to sink into the mantle.

Slide

Type of mass movement of downhill weathered rock material, occurring in a cohesive unit with minimal internal dislocation and deformation.

Slope overloading

Slope becoming overloaded with material, increasing pressure and causing it to fail.

Slope stability analysis

Analysis of the safety of a slope, for example a hillside, railway embankment, or landfill site.

Soil creep

Slow movement of soil on gentle slopes due to expansion and contraction of soil particles.

Solifluction

Gradual movement of wet soil down a slope in areas underlain by frozen ground.

Subduction zone

Area where oceanic crust is forced under continental crust and sinks into the mantle as plates converge.

Thermal expansion

Weathering found in areas with large diurnal temperature range, causing rocks to expand and contract, weakening outer layers.

Transform

In plate tectonics, plates moving past each other side by side, often causing earthquakes.

Unroofed

Upper layers of rock erode, allowing lower layers to relax and crack.

Volcanoes

Fissures in Earth's crust through which magma reaches the surface, with four main types: acid lava cone, composite volcano, fissure volcano, and shield volcano.