Coasts - Theme 2 - GEOLOGY Flashcards
What are the two sub sections of geology
- Lithology
- Structure
What is lithology
- The way rocks are made up
- resistant?
- permiability
- chemical form
What is Structure
-The way rocks are disposed
What are the three rock types
- Igneous
- sedimentary
- metamorphic
How are igneous rocks formed
- Rocks are pushed deep down into the earth
- They melt and become molten (magma)
- When errupted from volcanos they become lava
- When they cool they become igneous
- Igneous rocks have CRTYSTALS
- because they cool quickly (earth surface is cool) they have SMALL crystals
- Igneous rocks in the earth have larger crystalls because it takes longer to cool
How are sedimentary rocks formed
- Sediment that is compacted under pressure to form a rock
- They are made up of grains
- Grains can be ANDULAR or GROUNDED
- They create pores
- IF PORES CONNECT THEY ARE PERMIABLE
How are metamorphic rocks formed
- Rocks that change over time
- Under pressure and heat the grains and minerals change
- This is called METAMORPHISM
- Metamorphic rocks are crystilline
- THEY HAVE LAYERS
- two factors effect the type of rock
- type of rock at START and the AMOUNT of heat and pressure
What are examples of igneous rocks
- basalt
- granite
- obsidian
What are examples of sedimentary rocks
- limestone
- sandstone
What are examples of metamorphic rocks
- marble
- slate
- gneiss
How does lithology effect erosion rates
- Resistance
- Permeability
- Faults or bedding planes
- Chemical composition
How does resistance effect erosion rates
- igneous and metamorphic rocks are hard
- harder to erode
- sedimentary rocks are easier to erode
How does permiability effect erosion rates
- more permeable means there are cracks and joints
- vunurable to salt crystilisation hyrualic action freeze thaw
- CHALK IS AN EXCEPTION AND GETS STRONGER
How does the physical make up of rock effect erosion rates
-more bedding planes and faults easier to erode
How does chemical composition effect erosion rates
- if chemically inert then slow
- ferrous - oxidation
- CaCO3 - carbonation
- Saltwater causes rocks like basalt to weather 14 times faster
How does structure and arrangement change erosian rates
-the strata in the rock deceide how organised the planes are and therefore erosion rates
How does horizontal strata effect erosion rates
- resist the erosion
- produce tall cliffs
How does vertical strata effect erosion rates
- weathering can lead to the rock becoming unstable
- erodes fast
How does seaward dip strata effect erosion rates
- leads to sheets falling into the sea
- only needs one part of the strata to erode then whole sheet is eroded
How does inland dip strate effect erosion rates
- more resistant to erosion and produces steep cliffs
- harder to erode
How does strata with well developed joints at right angles effect erosion rates
- gives a place to attack
- is a weakness
- faster
