Cliff collapse

Cliffs collapse for a number of reasons, including the rate and type of weathering acting upon the front edge of the cliff or the cliff face, and the rate and type of erosion occurring at the cliff base.  These 2 processes are dependent upon various factors including:
The size and power of the waves attacking the coastline
The material that makes up the coastline - weak clays will collapse quicker than more solid Granite
The STRUCTURE of the rock, rocks with vertical faults and horizontal bedding planes are more susceptible to erosion.
The climate of the area - warm humid climates favour more chemical weathering.
Where the waves strike the cliff face.

Cliffs can collapse in a number of different movements, called MASS MOVEMENTS;

Slumping/Rotational slips

Here, water can build up in soils and add weight to it.  The material moves down slope along a curved surface, leaving behind an exposed scarp face below the head of the slump, and producing a hummocky toe at the foot.

Rock falls

Here, large and small fragments of rock are continually weathered and eroded until they separate and fall from the cliff as whole parts.  In Britain this is often due to freeze thaw weathering.

Land slides

Where rocks are laid down in beds that slope (dip) down towards the sea whole layers can slide down slope along a slide plane.

Mudflow

This is where saturated soil and weak rock flows down a slope and produces a lobe - sometimes called a solifluction lobe.