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 through Waves attack the headland cutting caves on each side

Tom Abbott, Biddulph High School and made available through Waves attack the headland cutting caves on each side

Tom Abbott, Biddulph High School and made available through Waves attack the headland cutting caves on each side

Tom Abbott, Biddulph High School and made available through 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 through Tom Abbott, Biddulph High School and made available through The arch enlarges until it collapses, leaving a standing rock called a stack

New arch forms

Tom Abbott, Biddulph High School and made available through Tom Abbott, Biddulph High School and made available through 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 through 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.