Rocks Flashcards
1
Q
Igneous
A
- intrusive (plutonic) = granite
- extrusive (volcanic) = basalt
- molten rock cools and solidifies
- deep within crust OR on surface
2
Q
Igneous - intrusive
A
- molten magma forces its way into rock cavities/ between layers of other rocks
- cools and solidifies deep in crust
- eventually come to surface as result of uplift or removal of overlying rocks
- granite
3
Q
Igneous - extrusive
A
- lava erupts from volcanoes/sea floor fissures
- cools and solidifies on surface
- basalt
4
Q
Granite
A
- dark grey colour
- coarse grained + has large crystals
- resistant to erosion
- batholiths
- cooled v slowly (crystals were given time to develop and grow)
- eg. The Leinster batholith
5
Q
Basalt
A
- most common on earths crust
- dark colour
- fine grained + small crystals (rapid cooling)
- cools quickly and solidifies
- eg. Antrim Derry plateau
6
Q
Sedimentary
A
- near earths surface
- land, lake beds, beneath the sea
- develop in layers called strata (sediments are deposited at over time at diff rates)
- lithification
- organic = limestone, coal
-inorganic = sandstone, conglomerates
7
Q
Lithification
A
The process that converts sediments into solid rock
1. Compaction (grains are squeezed together by weight of overlying sediments)
2. Cementation(individual particles bond to one another by a cementing agent, eg silica/calcium carbonate)
8
Q
Sedimentary - inorganic
A
- formed from sediments that were broken down by weathering and erosion of pre existing rocks
- sandstone
- conglomerates
9
Q
Sedimentary - organic
A
- formed from the remains of once living organisms (sea creatures, plants etc)
- limestone
- coal
10
Q
Inorganic - sandstone
A
- second most common rock type in Ireland
- formed from grains of sand that were deposited on land/shallow sea
- deposits later lithified
- layers separated by bedding planes
- eg. Galtee mountains
11
Q
Inorganic - conglomerates
A
- association with sandstone
- stones and pebbles deposited by flood water
- pore spaces between were filled with sand and mud
- lithified
12
Q
Organic - limestone
A
- composed almost entirely of calcium carbonate (varies in appearance)
- stratified rock laid down on the bed of warm, clear, shallow sea
- formed from skeletal remains of marine creatures (fish,urchins,coral)
- over time, compressed by their own weight + cemented by calcium carbonate to form solid rock (fossils)
- karst - Carboniferous limestone
- most common rock in Ireland
- eg. Burren
13
Q
Organic - chalk
A
- pure, soft white limestone
- laid down far from sediments that originated on land so not to be contaminated
- once covered most of Ireland (since been eroded)
- eg Antrim Derry plateau (protected by layer of basalt)
14
Q
Metamorphic
A
- other rocks that have changed with heat and/or pressure
- physical change (appearance)
- chemical (make up)
Two types :Contact (thermal) Regional - limestone —> marble
- sandstone —> quartzite
15
Q
Contact (thermal) metamorphism
A
-occurs when there’s an intrusion of molten magma into the crust
- the rocks are changed by heat alone
- localised as intrusion ‘cooks’ only the surrounding rocks
- the metamorphic rocks that surround the intrusion = an aureole
