Topic 4: Evolving Physical Landscape Flashcards
What are igneous rocks?
They are formed when molten rock (magma) from the mantle cools down and hardens, they are usually the strongest of the three rock types.
What are sedimentary rocks ?
They form when layers of sediment are compacted together until they form solid rock, there are two types:
- Carboniferous limestone and chalk are formed from tiny shells and skeletons of dead sea creatures, limestone is strong and chalk much softer
- Clays and shales are made from mud and clay minerals, they are soft
What are metamorphic rocks ?
These rocks are formed when other rocks (igneous, sedimentary or older metamorphic) are changed by heat and pressure, they become more compact and harder.
How have active volcanoes shaped the uk?
- 520 million years ago the uk used to be much closer to the plate boundaries, this meant that active volcanoes formed here.
- These volcanoes created igneous rocks
How have plate collisions shaped the uk?
- Plate collisions created mountainous areas in Scotland
- The igneous rock there is hard
How have plate movements shaped the uk?
- Britain used to be partly underwater, this meant that areas underwater formed chalks and clays (weak rocks) whereas northern areas above water formed much stronger rocks like Carboniferous limestone
How have glaciers shaped the uk?
- Glaciers used to be in Scotland, they eroded to create valleys
- When they melted they deposited a mineral called tilt in southern areas as the glacier water ran over leaving tilt behind
What does impermeable mean?
A rock that cannot have water run through it
Physical processes that have shaped upland uk?
- Freeze thaw occurs on steep valleys, rock falls create a screen slope.
- Most rocks upland are impermeable : therefore there are a lot of rivers meaning more erosion takes place
- Glaciers formed u shaped valleys : in the u shaped valley lies a misfit river
Physical processes that have shaped lowland uk?
- Meanders : They form on the impermeable rock
- Wet climate : lots of rain causes flooding of the river which means silt is deposited on the valley floor creating a flood plain
- Dry valleys : when the uk had a cold enough temperature for glaciers
Distinctive landscapes formed from human activity ?
- Agriculture : cleared forests to make space for farming, hedgerows have been used to mark out fields
- Forestry : most of the uk used to be covered in deciduous forests, this is mostly gone now
- Settlements : concreted roads have effected drainage patterns, rivers have been diverted to underground tunnels and rivers have been straightened or had embankments to prevent flooding
Concordant?
A coastline with only one type of rock
Discordant?
A coastline with multiple types of rock, creating headlands and bays
How are headlands and bays formed?
- Must be on a discordant coastline
- Less resistant rocks are eroded to create bays
- The wave energy is then directed towards the more resistant rock which will be eroded at the bottom to create steep cliffs
Rotational slumping?
- The bottom layer of rock is impermeable (clay) but the top layer is permeable (sand).
- When it rains water accumulates at the boundary and lubricates it
- The permeable material (sand) will become saturated and slip rotationally
Mass movement : rock slides?
- Joints holding the rocks together face the sea diagonally
- Erosion occurs at the base or weathering at the top of the cliff
- The cliff becomes unsupported
- The rocks slide down into the sea
Hydraulic action?
- Cracks form at the base of the cliff
- Air get trapped in the cliff
- As the waves hit the cliff it compresses the air increasing the size of the crack
- The air blasts out creating more cracks