Prelim Revision

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Prelim Revision Lithosphere and RLR
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Coasts

• Characteristic features
• Erosion
• wave-cut platform
• Cave
• Blowhole
• Arch
• Stack
• Stump
• Headlands and bays

• Deposition
• Spit
• Sandbar
• Lagoon
• tombolo

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Recap of Coastal Erosional Processes
Match them up!
A2 B3 C4 D1
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Explain the formation of this feature (7 marks)
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As waves crash against a cliff, they wear away
the rock to form a wave cut notch (an
indentation in the rock at sea level) (1), by the
processes of hydraulic action (1) and corrasion
(1). This is known as undercutting (1). As the
notch increases in size, the weight of rock above
is unsupported (1) and becomes unstable and
eventually the overhanging area of cliff
collapses into the sea (1). The continual
action of the waves against a cliff can result in
the formation of a wave cut platform (1). This is
a gently sloping area of rock at the base of a
cliff, and is the end product of a long, slow
process of erosion.
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Headlands, the areas of hard rock which jut
into the sea, erode slowly in stages.   The
continuous action of waves against headland rock
attacks at the weakest points cracks and faults
(1). Hydraulic action and corrasion (1) eat into
these cracks, and over time they widen
sufficiently to become caves (1).   As the
process continues, a cave may expand so much that
it cuts right through the headland to create an
arch (1). Waves and weather continue to erode the
structure of an arch, particularly at its base
(1) as the rock wears away, the arch is unable
to support its roof, which eventually collapses
into the sea (1).  
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When a mass of rock becomes entirely detached
from the mainland, it becomes a stack (1).
  Standing independently, a stack will continue
be weathered and eroded (1) until it finally
leaves behind a stump (1). Another feature of
the coastline is a blowhole. This is a vertical
opening in a cave, caused by weathering and
erosion - in certain wave and weather conditions,
sea water is forced through the blowhole,
resulting in a upwards spray (1).
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Coastal Deposition

• Longshore drift
• When waves hit a shore at an angle (usually as
  a result of prevailing wind direction) the swash
  moves up the beach diagonally, taking with it
  sand and sediment.
• The backwash, as a result of gravity, takes the
  most direct route back to the sea at 90 degrees
  to the shore.
• Gradually, the zigzag' movement of longshore
  drift carries material along the beach. Longshore
  drift helps to create several coastal features.

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(No Transcript)
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A spit is a long narrow beach growing at a gentle
angle out to sea or across a river mouth. It has
a sandy beach on the seaward side with sand dunes
inland. A spit forms when there is a sudden
change of direction in the coastline and where
the sea is shallow and calm.   Sometimes a spit
will grow across a bay to form a feature called a
sandbar. The loch behind the bar has fresh not
salt water in it, showing that the sandbar was
formed several hundred years ago.
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When a spit grows out from the mainland to meet a
separate island, it is known as a tombolo.
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Identification of coastal features from OS maps
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Upland Limestone

• Characteristic features
• Limestone pavement (with clints and grykes)
• Swallow hole
• Shake hole
• Cave
• Gorge
• Scar and Scree
• Stalagmite and Stalactite

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• Limestone pavement
• Areas of bare limestone, scraped clear of soil
  and glacial drift by glacial abrasion
• Many limestone pavements were exposed during the
  last glaciation and have subsequently been eroded
  and dissolved by rainwater
• Joints formed in limestone as it dries out or as
  pressure is released
• Lines of weakness are susceptible to chemical
  weathering
• Carbonation and solution have widened and
  depended bedding planes and joints to produce a
  distinctive landscape of clints (raised blocks)
  and grykes (deep gaps)
• Carbonation is the dissolving of limestone and
  its removal in solution as calcium hydrogen
  carbonate
• Solution occurs when rainwater, dilute carbonic
  acid, dissolves minerals in the rock and carries
  them away in solution

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Grikes

• When rain falls onto the surface of limestone,
  it seeps into the many joints. As it does so, it
  dissolves the rock on either side by chemical
  weathering, making the joint wider and wider.
  This happens over the whole surface of the
  limestone so that eventually the surface is
  broken up into a series of rectangular blocks
  separated by wide, deep cracks (grikes).

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Stalactite

• The water that drips down into caves is laced
  with calcium carbonate that has dissolved on its
  passage through the rock.
• The water drips from the cavern roof very slowly
  so that some of it evaporates.
• When it evaporates, it leaves behind the calcium
  carbonate, which is deposited on the cave roof.
• The deposits build up to form fingers of
  dripstone that grow downwards into the cave
  stalactites.

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Stalagmite

• Some of the water drips onto the cavern floor
  where it also evaporates.
• It leaves behind calcium carbonate here as well,
  which is deposited as dripstone on the cavern
  floor.
• As more water drips down, more is deposited,
  forming fingers of dripstone that grow upwards
  from the cavern floor stalagmites.

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Swallow Hole
Caused by a river/stream flowing off of
impervious rock onto the weak pervious rock. The
water ends up eroding the rock and caving in to
form a swallow hole.
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Gorge
Cave
Enlarged joints and bedding planes provide lines
of weakness where erosion can set in. Underground
streams contribute to the process of erosion and
the formation of long networks of caves, caverns
and tunnels.

• Massive collapse of the roofs of underground
  caves as carbonation and solution continue to eat
  away at underground limestone. Eventually leaving
  a roofless cave, or a gorge

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What feature is this and how was it formed?
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Scar a short steep slope which is generally
bare rockScree loose fragments of rock which
have accumulated on a hillside

• More likely in well-jointed rock
• Water enters cracks and joints
• When temperature drops this water freezes and
  expands
• This process slowly widens cracks permitting more
  water to enter in future
• The process of enlargement of these cracks
  continues until the rock fragment breaks off and
  falls to the ground
• Larger fragments tend to occur higher up the
  slope.

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Identification of limestone features from OS maps
Identifying Limestone Features on an O.S map
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River seemingly coming from nowhere
intermittent drainage
limestone pavement
swallow hole
gorge
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Rural Land Resources

• Coastal Dorset
• Features, problems/conflicts, solutions/protection
  .

• Limestone Yorkshire Dales
• Features, problems/conflicts,
  solutions/protection.