Flashcards in Erosional landforms Deck (14):
Destructive waves break on cliff, undercutting by wave action forms wave-cut notch. Rock strata above weakened, it collapses producing a steep profile. Debris from foot of cliff removed by wave action, cliff retreats inland parallel to coast.
Horizontally bedded strata
Undercutting of lower rock layers causes rockfall, parallel retreat inland due to undercutting then collapse of rock layers above. Has steep/near vertical profile.
Difficult to dislodge as rock layers angled away from weathering/wave action, rocks only loosened. Profile lowered by weathering/mm. Steep profile.
Undercutting removes basal support and the layers are loosened by weathering so slide along the bedding planes into the sea. Profile matches angle of strata.
Undercutting, collapse, at base a gently sloping platform is cut, dissected by abrasion. Friction slows waves, so they break on platform not cliff base, undercutting stops.
Rock outcrops lie perpendicular to coastline. Weaker erode rapidly (bays), resistant rocks remain (headlands).
Bay depth & width
Width- band of weaker rock, depth-differential rates of erosion between the two rock types.
Lie parallel to coastline, resistant rock seaward so protects weaker rock inland, Bays/coves eroded at fault lines.
Isle of Purbeck, Dorset
Discordant east-facing and concordant south-facing. Irregular shaped coasts refract waves as their increasingly parallel configuration becomes disturbed.
Wave refraction (headlands)
Waves are slowed by friction in shallower headland water, the part of the crest in deeper water moves faster, so the wave refracts around headland and orthogonals converge focusing energy/erosion.
Wave refraction (bays)
Orthogonals diverge, energy is dissipated so waves deposit their load. Waves breaking on headland approach at angle so LSD movement of sed into bays.
Narrow/steep sided inlets, form from faults eroded rapidly by wave action. Huntsman's Leap, Pembrokeshire is 35m deep.
Caves/mining shafts enlarged by erosion may suffer roof collapse, forming a vertical shaft to the cliff top. Storm waves force plumes of aerated water out. Trevone, Cornwall, 25m deep blowhole.