Coastal Recession Flashcards
What does coastal recession refer to?
How fast a coastline is moving inland.
What is the key factor of coastal recession?
Lithology or rock type.
What are the three major rock types?
Igneous, sedimentary, metamorphic.
Three examples of an igneous rock
Granite
Basalt
Dolerite
Three example of a metamorphic rock
Slate
Schist
Marble
Three examples of a sedimentary rock
Sandstone
Limestone
Shale
At what rate does an igneous rock erode and why?
Very slow. Less than 0.1cm per year.
Igneous rocks are crystalline, and the interlocking crystals make for strong, hard erosion - resistant rock.
Igneous rocks such as granite often have few joints, so there are limited weaknesses that erosion can exploit.
At what rate do metamorphic rocks erode and why?
Slow. 0.1-0.3cm per year.
Crystalline metamorphic rocks are resistant to erosion.
Many metamorphic rocks exhibit a feature called foliation, where all the crystals are orientated in one direction, which produces weaknesses.
Metamorphic rocks are often folded and heavily fractured, forming weaknesses that erosion can exploit.
At what rate do sedimentary rocks erode and why?
Moderate to fast. 0.5 -10 cm per year.
Most sedimentary rocks are clastic and eroded faster than crystalline igneous and metamorphic rocks.
The age of sedimentary rocks is important, as geologically young rocks tend to be weaker.
Rocks with many bedding planes and fractures, such as shale, are often most vulnerable to erosion.
What is unconsolidated material?
Sediment that has not been cemented to form solid rock, a process known as lithification.
How fast does boulder clay on Holderness Coast erode?
2 - 10m per year
What can erosion and weathering resistance be influenced by?
How reactive minerals in the rock are when exposed to chemical weathering.
Whether rocks are clastic or crystalline, the latter are more erosion resistant.
The degree to which rocks have cracks, fractures and fissures, which are weaknesses exploited by weathering and erosion.
How can cliff profiles be influenced by the permeability of the strata?
Permeable rocks allow water to flow through them, and include many sandstones and limestones.
Impermeable rocks do not allow groundwater flow and include clays, mudstones and most igneous and metamorphic rocks.
What is pore water pressure?
Pore water pressure is an internal force within cliffs exerted by the mass of groundwater within permeable rocks.
Why is permeability important?
Permeability is important because groundwater flow through rock layers can weaken rocks by removing the cement that binds sediment in the rock together.
It can also create high pore water pressure within cliffs, which affects their stability.
