1.5Understand how ocean waves and currents change the face of coastal areas.

1.5.1Define the term spit. (P ) Spit A ridge of sand running away from the coast, usually with a curved seaward end. Spit grows in the prevailing direction of longshore drift. Ends are curved by the action of waves in different directions Longshore drift consists of the transportation of sediments (clay, silt and sand) along a coast at an angle to the shoreline, which is dependent on the prevailing wind direction.

Spit

What can you tell about the direction of long shore drift?

Sea Cave A sea cave is a large, natural hollow in a headland caused by wave erosion

Sea Arch A sea arch is a feature which results when two caves occurring on either side of a headland are cut. Arches are usually temporary, until the roof collapses and isolates the seaward end

Sea Stack A sea stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by erosion. Stacks are formed over time by wind and water.

1.5.3 Describe how sea caves, sea arches and sea stacks are formed. (P. 48) In order for these three coastal structures occur on “emerging” coast lines, there must be steep cliffs & a headland. 1 st Sea caves form, 2 nd sea arches form and 3 rd sea stacks form.

What is a Coastal Headland? A headland is a coastal landform, a point of land usually high and often with a sheer drop, that extends out into a body of water.

1.5.3 Describe how sea caves are formed. (P. 48) 1. Waves strike the headland first 2. Waves refract around the headland and put hydraulic pressure on the sides of the headland. 3. Erosion of the weak portions create caves & blow holes in the sides of the headland.

1.5.3 Describe how sea arches are formed. (P. 48) 4. Eventually the sea caves get deeper until they connect inside the headland forming a complete passage way or tunnel or “arch” through the head land It is difficult to see or imagine from the top view. However the side view provides a better picture.

1.5.3 Describe how sea stacks are formed. (P. 48) 5. Continuous erosion causes the collapse of the ground over the arch 6. This leaves a pillar or column or “STACK” of land standing alone where the headland was. Sea stacks are common in eastern Canada. Many have plant growth on top.

* 1.5.4Analyze the processes that result in the straightening out” of an irregular coastline. (P. 48) [emerging] 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 & bay bars. However the result is similar in that headlands are reduced in size.

1.5.4Describe the three process by which wave action erodes coastal areas. (P.31 * same as three for river erosion) Hydraulic pressure = The pounding force of water/waves 2.Corrosion = Minerals such as calcium carbonate & limestone dissolve in the water 3.Abrasion = rock & sand particles suspended in the water bump, grind, scrape & gouge surfaces the water hits

* 1.5.4Analyze the processes that result in the straightening out” of an irregular coastline. (P. 42 questions # 11 & 12) [submerged] 1. Weathering of Headland What forces cause the weathering & erosion? Hydraulic Corrosive Abrasive 2.Transportation of silt How is silt transported? Longshore Drift Waves Currents 3.Deposition of silt Where does deposition occur? Bay beaches; filling inlets Bay bars; closing off inlets 4.Summary: Submerged coasts straighten due to erosion.

Video Sea stacks of NL