Basic Rock Info
- what is a rock?
made of minerals
igneous (formed from heat)
- ‘fire’, basalt (on ocean floor, part of oceanic crust) and lacks in silica. common in shield volcanoes. rounded from erosion.
- pumice (exfoliating!). as rock cools, the gas escapes and thus it’s so porous.
- granite (brown/red/pink). formed from liquid - cooled down, cools slowly (therefore you get crystals).
- obsidian (igneous surface rock)
metamorphic (undergone transformation from heat and pressure)
- slate: hard and thin. chalkboards! doesn’t let water through, therefore used for roofing tiles
sedimentary (made from sediment, material that is deposited in water)
- sandstone. colours vary because of rust (there’s parts of iron in it, reacted with water and rusted! and since sandstone is from sand, we’re basically lying on rust.
- mudstone: made of mud.
- coal: remnants of sea creatures (one of the only rocks that can burn)
- limestone (heated and put under pressure = marble) (concrete!)
- chalk (used not only because of its white colour, but because it can rub off)
- preserved, altered remains in rock
coprolite: fossilized dung!
limestone and its features: mulu, sarawak - bat caves. bats: guano (excrement).
- when you cave in limestone, it’s called spelunking
- and limestone is full of these vents, because of chemical weathering
- impermeable → can’t pass through
permeable → can get through, and is porous sometimes
difference between porous and permeable → permeable allows liquids through, but porous just has holes/gaps
- pervious → water can pass through cracks, called joints. porous = holes, pervious = joints.
- so a spelunker can use the perviosity of the rock - but not the porosity.
if there are no cracks → impervious.
- antonym of porous → non-porous.
porous rocks → sedimentary, layers of undersea sediment.
- clay: IMPERMEABLE, but POROUS (the pores aren’t connected)
- CARBONATION dissolves joints in rocks, and widens them.
- the dips are called grykes, and the flat surfaces clints. caved-in holes are called swallow holes - formed because two cracks cross over and the water goes down, over time this widens into a hole.
- stalactites, from the top; stalagmites, from the bottom (grow upwards)
when a stalactite and stalagmite meet, it’s called a column.
- calcium carbonate is the building block of limestone!
- doline - sunken in depression in the ground
- THESE SYSTEMS ARE CALLED KARSTS