GEOLOGY REVISION
Igneous: Meaning “from fire”, they are created when lava or magma cools at different rates. They contain crystal such as clear quartz, black mica and white/pink feldspar. Can be plutonic/intrusive where magma cools slowly underground, or volcanic/extrusive where they cool quickly above, often after an eruption.
-Used for decorative walls, floors, or desktops
-Eg. Pumice, Granite, Basalt, Obsidian, Gabbro
Sedimentary: Literally resembling, containing, or forming by a collection of sediments.
-3 main characteristics: No crystals, layers, grains
-Identified by layering, size and type of sediments.
-They all form underwater.
Sediments= Deposited piece of weathered rock or plant/animal remains
-Layers caused when grains/pebbles of different sizes settle at different times.
-Used for statues, paving, buildings and statues, but not as common due to acid rain wear. Polished limestone is too slippery for paving.
-Type of rock formed depends of place of formation and type of material
-Coal creates in forest floor where bottom layers are dried and temperature rises leaving coal
-Conglomerate formed in fast flowing river
-Mudstone formed in a still lake
-Limestone and coal aka biological rocks
-Eg. Breccia, Sandstone, Limestone, Shale, Mudstone, Siltstone, Gypsum, Coal, Conglomerate
Metamorphic: Meta meaning change and morphe meaning form.
Parent Rock Metamorphic Rock Main Cause of Metamorphism
Shale Slate Pressure
Limestone Marble Heat
Granite Gneiss Pressure
Sandstone Quartzite Heat
Conglomerate Metaconglomerate Heat
-Can be made of any other rock type
-Buried deep underground, change caused by heat from volcano and pressure from crust
-Used for statues, tables, roofs, slates, tiles, roads
-May be platy or flaky, distinct colour banding where minerals are squeezed into layers, distinct folding due to pressure
-Eg. Quartzite, marble, slate, schist, gneiss, Phyllite, Metaconglomerate
Weathering, Erosion:
-Sea action, wind, blasting of sand and soil, acid rain, and chemical reactions between water and ground
-Expansion of freezing water causes widening cracks which eventually break the rock
-Weathering: Where rocks are broken down into smaller pieces
-Erosion: Transportation of weathered rock
-Deposition: The weathered rock is laid down or deposited. Eg. From slowing wind or water
Rock Cycle Summary: Magma, crystallization, igneous, to weathering, erosion, deposition, to sediment, compaction and cementation, sedimentary, heat and pressure, metamorphic, melting, magma.
Layers of the earth: Crust, mantle, outer core, inner core.
Minerals: (rocks are made of minerals)
-Identified by characteristics including colour, lustre, transparency crystal system, crystal habits, cleavage, fracture, hardness, specific gravity, streak, other characteristics, associated minerals, notable occurrences, best field indicators.
-Rocks are composed of different minerals
-Most minerals contain crystals
Crystals: refer to previous revision
