lOMoARcPSD|11700591
‘Explain the formation of geos and blowholes’
A geo is a steep-sided narrow inlet in the cliff due to weakness in the rock, such as joints and
faults
The weak points on a cliff face are eroded more rapidly by wave action than the surrounding
more resistant rock
Hydraulic action is significant as it forces air and water into joints, weakening the rock strata
Abrasion helps to form a geo as sediment would have widened the gully
E.g. Huntsman’s Leap, Pembrokeshire, 35m deep
If part of the tunnel-like cave collapses along a master joint it may form a vertical shaft that
reaches the cliff top – blowhole
During storm conditions, large waves can force spray out of the blowhole as plumes of white
aerated water
e.g. Trevone in Cornwall which formed a 25m deep blowhole due to roof collapse
A geo is a narrow, steep sided inlet, which can be found within a cliff due to lines of weakness in the
rock, such as joints and faults. These weak points are eroded more rapidly by wave action (kinetic
energy), than the more resistant rock surrounding it. Hydraulic action is particularly significant as it
forces air and water into joints, and weakens the rock strata, together with abrasion (the scouring of
the rock face by other particles carried in the approaching wave) and attrition (wearing down of
rocks and pebbles as they rub against each other, making them smaller and rounder, eventually
producing sand). Glacier movements can also cut depressions in steep rock formations that may
erode to form a geo. An example of a geo is Huntsman’s Leap, which is located in Pembrokeshire. It
is 35m deep and has eroded along a large joint in the carboniferous limestone.
If part of the roof of a tunnel-like cave collapses along a master joint, it may form a vertical shaft that
reaches the cliff top. This is known as a blowhole. During storm conditions, large waves can force
spray out of the blowhole as plumes of white, aerated water. Blowholes may also be associated with
mining shafts or the collapse of a cave roof. The same applies to geos. A particularly good example of
a blowhole can be found on Cornwall’s north coast. It is called The Trevone Bay Round Hole. It is
25m deep and was formed after thousands of years of erosion. As a result, the walls are extremely
unstable.
‘Explain the formation of geos and blowholes’
A geo is a steep-sided narrow inlet in the cliff due to weakness in the rock, such as joints and
faults
The weak points on a cliff face are eroded more rapidly by wave action than the surrounding
more resistant rock
Hydraulic action is significant as it forces air and water into joints, weakening the rock strata
Abrasion helps to form a geo as sediment would have widened the gully
E.g. Huntsman’s Leap, Pembrokeshire, 35m deep
If part of the tunnel-like cave collapses along a master joint it may form a vertical shaft that
reaches the cliff top – blowhole
During storm conditions, large waves can force spray out of the blowhole as plumes of white
aerated water
e.g. Trevone in Cornwall which formed a 25m deep blowhole due to roof collapse
A geo is a narrow, steep sided inlet, which can be found within a cliff due to lines of weakness in the
rock, such as joints and faults. These weak points are eroded more rapidly by wave action (kinetic
energy), than the more resistant rock surrounding it. Hydraulic action is particularly significant as it
forces air and water into joints, and weakens the rock strata, together with abrasion (the scouring of
the rock face by other particles carried in the approaching wave) and attrition (wearing down of
rocks and pebbles as they rub against each other, making them smaller and rounder, eventually
producing sand). Glacier movements can also cut depressions in steep rock formations that may
erode to form a geo. An example of a geo is Huntsman’s Leap, which is located in Pembrokeshire. It
is 35m deep and has eroded along a large joint in the carboniferous limestone.
If part of the roof of a tunnel-like cave collapses along a master joint, it may form a vertical shaft that
reaches the cliff top. This is known as a blowhole. During storm conditions, large waves can force
spray out of the blowhole as plumes of white, aerated water. Blowholes may also be associated with
mining shafts or the collapse of a cave roof. The same applies to geos. A particularly good example of
a blowhole can be found on Cornwall’s north coast. It is called The Trevone Bay Round Hole. It is
25m deep and was formed after thousands of years of erosion. As a result, the walls are extremely
unstable.
