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
-pressure water experiences at a particular point below the water table due to the weight of the water above it
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
-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
