Erosion Revision Quiz

what are the types of Erosion

Hydraulic Action Waves breaking at the [blank_start]foot[blank_end] of a cliff force air in cracks to be [blank_start]compressed[blank_end]. Loose rocks are dislodged and removed. When the wave [blank_start]retreats[blank_end] the compressed air rushes out of the crack and [blank_start]can[blank_end] further weaken faults in the cliff face. Where velocity is [blank_start]high[blank_end] e.g. the [blank_start]outer[blank_end] bend of [blank_start]meaner[blank_end], hydraulic action can remove material from the [blank_start]banks[blank_end] which may lead to [blank_start]undercutting[blank_end] and river bank collapse. Near waterfalls and rapids, the force may be [blank_start]strong[blank_end] enough to work on lines of [blank_start]weakness[blank_end] in joints and bedding planes until they are eroded.

Cavitation Cavitation is a [blank_start]rare[blank_end] form of hydraulic action and the [blank_start]sudden[blank_end] and [blank_start]violent[blank_end] implosion of gas bubbles caused by this process [blank_start]shatters[blank_end] banks extremely rapidly. The resultant shockwaves hit and [blank_start]slowly[blank_end] weaken the banks. This is the [blank_start]slowest[blank_end] and [blank_start]least[blank_end] effective process.

Abrasion/Corrasion Corrasion is when rock caught up in [blank_start]surging[blank_end] waves are hurled at a cliff face – causing it to be chipped and gauged. Abrasion is the [blank_start]sandpaper[blank_end] effect of loose rocks being scraped along bare rock. It often [blank_start]smooths[blank_end] and polishes the rock. The sediment carried by a river scours the bed and banks. Where [blank_start]depressions[blank_end] exist in the channel floor the river can cause [blank_start]pebbles[blank_end] to spin around and turn hollows into potholes. This process is most effective during times of [blank_start]flood[blank_end] and is the major method by which the river erodes both vertically and horizontally. If there are hollows in the riverbed, pebbles are likely to become trapped. Turbulent eddies in the current can swirl pebbles around to form potholes. This form of erosion occurs most often during times of [blank_start]higher[blank_end] river flow, bed load being used as an abrasive agent, scratching and scraping of the solid bedrock.