2.1 Flashcards
Why do igneous rocks erode slowly?
- crystalline structure; interlocking crystals make rock harder
- igneous rocks have few joints; limited weaknesses for erosional processes to exploit
Differences in composition of intrusive vs extrusive igneous rocks
- intrusive solidify at depth, extrusive at surface (volcanic eruptions)
- intrusive is almost always crystalline, extrusive may be partly glassy
Why do metamorphic rocks erode slowly?
- are crystalline in structure
What weaknesses are there in metamorphic rocks?
- can exhibit foliation; crystals orientated in only one direction
- can be heavily folded and fractured; faults can be exploited
What are clastic sedimentary rocks?
Rocks made up of pieces of pre existing rocks that are compressed together
What geological factors can affect rate of erosion?
- permeability of rock
- linked with hardness (determined by rock type)
- age of rock (younger is weaker)
- whether reactive minerals are present in the rock
- eg calcite, which dissolves in water
Where are sand dunes found?
Runkerry
West of Giants Causeway
What is the name of the major headland?
Portrush
What are the Skerries?
Group of volcanic islands off North Antrim coast
What is present at White Rocks?
White chalk cliffs topped with basalt
What process has exposed the chalk at White Rocks?
- Tectonics uplift
- Dip changed to landward
- now the lower chalk strata is being eroded rather than the basalt cap
What is the general geological structure of the North Antrim Coast?
- top layers are composed of basalt
- as a result of volcanic activity 60 mya
- covers most of North Antrim Coast
- lower layers are softer sedimentary rocks
- laid down by warm shallow ocean millions of years ago
What sort of sedimentary rocks are present in Northern Ireland?
- sandstone
- chalk
