Sea landforms

An opening or hollow in the rock at the foot of a cliff

A weak spot in the rock, such as a crack, will be attacked by the hydraulic action of the waves, compressed air and abrasion. The crack gets larger and develops into a small cave.

A passage or tunnel that runs right through a headland

Either where a cave is deepened and enlarged by erosion so that it cuts through to the other side of the headland or where two caves on opposite sides of a headland meet.

a pillar of rock that is cut off from the headland or cliff

When the waves erode the base of a sea arch, they widen it. Eventually the roof is unable to support itself and it collapses, leaving the former tip of the headland cut off as a sea stack. If the base of the sea stack is eroded, it will collapse to leave a stump of rock that is visible at low tide.

A passage that links the roof of a cave with the surface of the cliff top

Air is trapped and compressed in a cave by powerful storm waves. This builds up pressure and helps to loosen and shatter the rock at the back of the cave. The rock eventually collapses, forming a blowhole.