influences on rates of coastal erosion Flashcards
how does wave refraction happen
-happens when waves move from deeper to shallower water
-wave speed decreases in shallower water, causing the wave to bend
-inner slows and outer continues at speed
what is wave refraction
reorientation of wave crests as waves enter shallow water so that the wave approaches parallel to the shore
what is unconsolidated sediment
-material like sand, gravel, clay and silt that hasnt been compacted/semented to become sedimentary rock (not undergone lithification)
-loose and easily eroded
what is pore water pressure
- the pressure exerted by water that fills the void spaces (pores) between particles in soil or rock.
what is the water table
-the level of water found underneath the ground
examples of igneous rock
-granite
-basalt
-dolerite
what is igneous rock
-crystalline meaning interlocking crystals make for strong, erosion resistant rock
-often have few joints so limited weaknesses
what are examples of metamorphic rock
-slate
-schist
-marble
what is metamorphic rock
-can be crystalline which are resistant but exhibit foliation (repetitive folding)
-often folded and heavily fractured which are weaknesses
what is foliation in crystalline rocks
-when crystals are all oreintated in one direction
-produces weaknesses
what are examples of sedimentary rock
-sandstone
-limestone
-shale
what is sedimentary rock
-most are clastic and erode fastest of all rock types
-geologically younger sedimentary rock tend to be weaker
-rocks with more edding places and fractures most vulnerable to erosion
what is the resistance of a cliff mostly influenced by
-the weakest rock type
what happens to weak uncosolidated layers
-slumping
what happens to groundwater flow in permeable vs impermeable rock
-flows through permeable sands but cannot flow through impermeable clay
-water flow along the sand/clay interface weakens material leading to slumping
examples of permeable rock
-sandstone
-limestone
example of impermeable rock
-mudstone
-most igenous and metamorphic rocks
why is the permeability of a rock important
-because the grounderwater flow through the layers can weaken rocks by removing cement that binds it together creating a high pore water pressure affecting stability
what is the morphology of a coastline mainly due to
-the geology
-the wave action
-how consolidated the rock is
what is wave action influenced by
-energy of wave
-length of fetch
-type of wave
-prevailing wind
-depth of nearshore and offshore
