Cameroon GCE A-Level Geology flashcards
Cameroon GCE A-Level Geology · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Mohs hardness scale
- A relative scale from 1 (talc) to 10 (diamond) ranking minerals by resistance to scratching; used in hand-specimen identification.
- Silicate tetrahedron
- The SiO4 building block of silicate minerals; polymerization of these tetrahedra controls cleavage, hardness and classification of rock-forming silicates.
- Bowen's reaction series
- The sequence of mineral crystallisation from cooling magma, from olivine and Ca-plagioclase at high temperature to quartz and K-feldspar at low temperature.
- Cleavage in minerals
- The tendency of a mineral to break along planes of weak atomic bonding, producing flat surfaces; number and angle of cleavage planes aid identification.
- QAPF classification
- A modal mineralogy diagram using quartz, alkali feldspar, plagioclase and feldspathoid proportions to classify igneous rocks such as granite, granodiorite and gabbro.
- Porphyritic texture
- An igneous texture with large crystals (phenocrysts) set in a finer groundmass, recording two stages of cooling at different depths.
- Graded bedding
- A sedimentary structure in which grain size decreases upward within a bed, typically deposited by a waning turbidity current.
- Metamorphic facies
- A set of mineral assemblages formed under a specific pressure-temperature range; examples include greenschist, amphibolite, granulite and blueschist facies.
- Foliation
- A planar arrangement of platy or elongate minerals in metamorphic rocks, produced by directed pressure; includes slaty, schistose and gneissose textures.
- Strike and dip
- Strike is the compass direction of a horizontal line on a plane; dip is the angle of steepest descent perpendicular to strike.
- Normal fault
- A fault where the hanging wall moves down relative to the footwall, caused by tensional stress and typical of divergent plate boundaries.
- Anticline
- A fold with the oldest rocks in its core and limbs dipping away from the axis, formed by compressional stress.
- Angular unconformity
- An erosion surface where tilted or folded older strata are overlain by younger, nearly horizontal beds, indicating a period of deformation and erosion.
- Cameroon Volcanic Line
- A Y-shaped intraplate alkaline volcanic chain trending NE-SW from Lake Chad through Mt Cameroon to Bioko and Annobón.
- Principle of superposition
- In an undisturbed sequence of sedimentary rocks, the oldest layer is at the base and the youngest at the top.
- Radiocarbon dating
- A method using the decay of carbon-14 (half-life 5,730 years) to date organic remains up to about 50,000 years old.
- End-Permian extinction
- The mass extinction about 252 million years ago that eliminated roughly 90% of marine species, the largest in Earth history.
- Pan-African orogeny
- A Neoproterozoic collision event about 600-550 million years ago that welded African cratons into Gondwana and formed Cameroon's Central African Fold Belt.
- Index fossil
- A fossil with a wide geographic range and short stratigraphic range, used to correlate and date rock layers.
- Walther's Law
- The principle that vertical facies successions in conformable sequences reflect the lateral migration of depositional environments over time.
- Transgression
- A sea-level rise causing the shoreline to move landward, producing a fining-upward sequence with offshore muds over nearshore sands.
- Formation
- The fundamental lithostratigraphic unit, a mappable body of rock with a defined type section and recognizable boundaries.
- Dendritic drainage
- A branching river network resembling a tree, developed on relatively uniform lithology with no strong structural control.
- Karst topography
- A landscape formed by dissolution of soluble rocks such as limestone, characterised by sinkholes, caves and disappearing streams.
- Longshore drift
- The movement of sediment along a coastline by waves approaching at an angle, causing a zigzag transport pattern.
- Lateritic bauxite
- An aluminium ore formed by intense tropical weathering that leaches silica and concentrates aluminium hydroxides; Cameroon's Minim-Martap deposit is an example.
- Cut-off grade
- The minimum ore grade that makes mining economically viable, determined by commodity price, mining and processing costs, and recovery.
- Acid mine drainage
- Acidic, metal-rich water formed when sulphide minerals such as pyrite oxidise in mine workings, requiring management and treatment.
- Lake Nyos disaster
- A 1986 limnic eruption that released carbon dioxide from Lake Nyos, Cameroon, killing about 1,700 people; degassing pipes now prevent recurrence.
- Ntem Complex
- The Archaean cratonic basement of southern Cameroon, composed of gneisses, granitoids and greenstone belts, correlating with Gabon and Congo cratons.
- Douala Basin
- A Cretaceous to Recent sedimentary basin in coastal Cameroon containing oil and gas, lignite and thick clastic sequences.
- Three-point problem
- A graphical method using the elevations of three points on a geological plane to determine its strike and dip.