Erosion of Emerging Coastlines
• In this lesson you will:
– 1.5.2 Define the terms sea cave, sea arch,
and stack. (k)
– 1.5.3 Explain how sea caves, sea arches and
stacks are formed. (a)
– 1.5.4 Analyze the processes that result in the
“straightening out” of an irregular coastline.
(a)
The Evolution of Sea Stacks
• Sea stacks are columns of land standing
in the ocean just off shore.
• They are created over a long period of
time after a series of other land structures
have eroded away.
The Evolution of Sea Stacks
• First sea caves are formed in a headland.
• Continued erosion turns sea caves in to
the second land feature, sea arches.
• Erosion and eventual collapse of the arch
top leaves a sea stack standing in the
ocean.
Sea Cave Formation:
• waves strike the headland first;
• waves refract around the headland and
put hydraulic pressure on both sides of the
headland;
• erosion of the weak portions create caves
and blow holes in the sides of the
headland. Page #48
Waves attack the
headland cutting
caves on each side
Sea Arch Formation
• Eventually sea caves, on alternate sides of
the headland get deeper until they connect
inside the headland forming a complete
passage way or tunnel or “arch” through
the head land.
Wave attack opens up the caves
on each side of the headland until
they join and form a natural arch
Sea Stack Formation
• Continuous erosion, of sea arches, causes
the collapse of the ground over the arch;
• this leaves a pillar or column or “STACK”
of land standing alone where the headland
was.
The arch enlarges until it
collapses, leaving a standing
rock called a stack
New arch forms
The old stack is worn down
into a stump
Another arch collapses
and a new stack is formed.
This is a huge Sea Cave, 250
meters wide and 15 meters deep
Sea Stack Formation
• Continuous erosion, of sea arches, causes
the collapse of the ground over the arch;
• this leaves a pillar or column or “STACK”
of land standing alone where the headland
was.
Tom Abbott, Biddulph High
School and made available
Waves attack the
headland cutting
caves on each side
Tom Abbott, Biddulph High
School and made available
Waves attack the
headland cutting
caves on each side
Tom Abbott, Biddulph High
School and made available
Waves attack the
headland cutting
caves on each side
Tom Abbott, Biddulph High
School and made available
Wave attack opens up the caves
on each side of the headland until
they join and form a natural arch
Tom Abbott, Biddulph High
School and made available
Tom Abbott, Biddulph High
School and made available
The arch enlarges until it
collapses, leaving a standing
rock called a stack
New arch forms
Tom Abbott, Biddulph High
School and made available
Tom Abbott, Biddulph High
School and made available
The old stack is worn down
into a stump
Another arch collapses
and a new stack is formed.
Tom Abbott, Biddulph High
School and made available
Straightening of Emerging
Coastlines
• emerging coastlines straighten in much the
same fashion as submerging coastlines;
• erosion of headlands creates sea caves, sea
arches and sea stacks instead of bay beaches,
spits and bay bars;
• however the result is similar in that headlands
are reduced in size which straightens the
coastline. Compare the headland length in figure 3.11 before
and after erosion.
Landforms Affect Human
Activity
• In this lesson you will:
– 1.9.1 Examine examples to illustrate how human
activity adapts to land forms and water forms.
– 1.9.2 Examine examples to illustrate how land forms
and water forms affect accessibility.
– 1.9.3 Justify a preference for the appeal of selected
landforms and water forms.
– 1.9.4 Propose a solution to a threat posed by selected
land and water forms.
•
Human adaptation
• Humans have adapted to most conditions
on earth.
• Look at many small fishing villages in
Newfoundland and you will see how
people adapted to build houses up cliffs
that overhang the ocean.
• The stilt houses of Bangladesh show how
humans have adapted to living in delta
regions.
• Assigned Readings
• "Storm surges in Bangladesh" on p. 50-51
in your text book.
Economic Proposal
• In this lesson you will learn:
• To develop a proposal for the economic
use of selected landforms or water forms.
(i)
Economic Proposal
• You will be expected to write an economic
proposal for a given land form or water
form.
• You could be asked to write a proposal for
a river with many large water falls or with
small rapids; you could be asked to write a
proposal for a mountain near the coast.
Consider the following when you do
a proposal
• The economic activity must fit the terrain. For example a
hydroelectric generating station on a slow meandering
old river might not be a good idea whereas boat tours
might be.
• How would the environment be impacted? Obviously
you would need an environmental impact study and a
means of reducing the impact on nature.
• Is the area accessible to people or machinery? You
must be able to access it to make money.
• How might building and erosion forces impact your
proposal in the short term and long term?
• What types of potential problems accompany the land or
water form. For example flooding accompanies old
meandering rivers.