UNIT 5 EXAM GEOLOGY CHAPTER 15

Describe the two processes that contribute to longshore transport.

Beach drift is when incoming waves hit the beach at an angle, causing a zigzag motion of the water and the sediment contained in it down the beach. The longshore current also contributes to longshore transport; as the longshore current is the current that runs parallel to the beach.

Describe the process of coastal upwelling. Why is an abundance of marine life associated with these areas?

Coastal upwelling occurs when wind blow surface waters laterally. Cold, nutrient-rich water from lower ocean layers moves upward to fill the space. There is an abundance of marine life in these areas because of the dense nutrient concentrations in these upwelled waters.

Briefly describe what happens when storm waves strike an undeveloped barrier island.

Waves may move sand from the beach to the offshore region or the dunes. Overwash may move sand as far as the bay side of the barrier island. The whole island is capable of moving sediment with whatever waves hit it.

Why do waves that are approaching the shoreline often bend?

Wave refraction occurs as part of the wave approaching at an angle becomes a shallow water wave, thus slowing down, while part of the wave is still a faster-moving deep water wave.

What is a beach? Distinguish between beach face and berm.

A beach is where sediment accumulates along the landward edge of an ocean or a lake. The beach face is the part of the beach that is wet and sloping, extending from the berm to the shoreline. The berm is relatively flat and adjacent to coastal dunes or cliffs; they mark a change in slope.

How is a mixed tidal pattern different from a semidiurnal tidal pattern?

A mixed tidal pattern is when there are two high tides and two low tides of unequal height during the day and a semidiurnal tidal pattern is when there are two high tides and two low tides of equal height during the day.

How is a marine terrace related to a wave-cut platform?

A wave-cut platform is generated as waves erode coastal cliffs over time. A wave-cut platform can become a marine terrace if it is uplifted by tectonic forces.

What is an observable feature that would lead you to classify a coastal area as emergent?

An elevated marine terrace.

Why is the shoreline considered an interface?

An interface is a boundary where different parts of a system interact; the shoreline is a boundary between the ocean processes and those found on land and in the atmosphere.

Why is deep-ocean circulation referred to as thermohaline circulation?

Deep-ocean circulation is a global circulation pattern that relies on temperature and density differences to determine if the current will flow at the surface or on the ocean floor.

Describe the formation of the features labeled in Figure 15.20 and Figure 15.21.

In Figure 15.20 we see a sea stack and a sea arch. These form due to wave erosion as refracted waves aggressively erode extending headlands. If there are caves on opposite sides of the headland, a sea arch with a hole in the middle of the rock may form. In Figure 15.21 we see a spit, a baymouth bar, and a tidal delta. A spit is formed as longshore transport generates an elongated ridge of sand that extends into a hook shape into a bay. A baymouth bar is also caused by longshore transport if a ridge of sand completely seals off a bay. A tidal delta is a bayward deposit of sand caused by the ocean breaking through the ridge of sand. 3. List three ways that barrier islands may form. They can originate as spits that were severed from the mainland, they may be formed when turbulent coastal waters deposit long ridges of sand, or they may be former sand dunes that had the areas around them flooded as sea level rose after the last glacial period.

How might building a dam on a river that flows to the sea affect a beach?

It would restrict the flow of continental sediments to the beach, depriving the beach of a sand source.

How do ocean currents influence climate? Provide at least three examples.

Ocean currents influence climate because the currents are major redistributors of heat and energy throughout the globe. Warm currents such as the Gulf Stream cause regions that would normally be cold to be warmer. For example, New York is warm for its latitude. Cold currents cause the air above them to be cooler. San Francisco is relatively cool in the summer because of the presence of the cool California Current off its coastline. Cold currents also increase the aridity of an area. The Peru Current off the coast of South America causes stable atmospheric conditions that resist cloud formation and moisture-bringing precipitation.

Describe or make a simple sketch of the ocean's conveyor-belt circulation.

See Figure 15.7. Warm surface waters flow from the mid-Pacific, through the Indian Ocean basin, and upwards to the North Atlantic. In the North Atlantic, these waters become more dense as they cool, and they sink to the ocean floor, where they flow back to the Indian and Pacific Oceans as deep-ocean currents.

How does the Coriolis effect influence ocean currents?

The Coriolis effect causes the deflection of the path of moving objects, including the path of surface currents, to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection generates the large ocean gyres that flow in a circular path in the oceans

Explain why an observer can experience two unequal high tides during one day

The Moon's position will vary with respect to the observer. If the Moon is located in a position where it pulls strongly on the tide in one part of the day and more weakly during the other part of the day, the observer can experience two unequal tides.

Describe the motion of a floating object as a wave passes.

The floating object will bob up and down as the water underneath it moves in a vertical circular pattern

Describe two ways in which waves cause erosion.

The force of the water in a wave exerts a great deal of pressure on rocks, causing rock fragments to break loose and enlarging fractures. Waves also cause erosion due to abrasion from rock fragments and large sediment carried by them.

Distinguish among shore, shoreline, coast, and coastline.

The shore is the area that ranges from the lowest tide level to the furthest reaches of land affected by storm waves, while the shoreline is the line that demarcates between land and sea. The coast is the area that extends from the shore to as far as ocean-related features can be found, where the coastline marks the coast's seaward edge.

How do the speed, length, and height of a wave change as the wave moves into shallow water and breaks?

The speed decreases while the length of the wave also decreases. The height increases, eventually breaking on the shore.

Are estuaries associated with submergent or emergent coasts? Explain.

They are associated with submergent coasts. As sea level rises, drowned river mouths that have been submerged become estuaries.

Distinguish between neap tides and spring tides.

When the Sun and the Moon are aligned with the Earth, both influence the tidal bulges, which will be greater than normal; this is a spring tide. When the Moon is in the first or third quarter position, the tidal bulges produced by the Sun are at right angles to those produced by the Moon, and these bulges will be smaller than normal. These are neap tides.

List three factors that determine the height, length, and period of a wave.

Wind speed, length of time the wind has blown, and fetch, which is the distance wind has travelled across the open water.

What is the effect of wave refraction along an irregular coastline?

You will find erosion of the headlands and deposition in the bays

What is the primary driving force of surface-ocean currents?

wind

What are two alternatives to hard stabilization, and what potential problems are associated with each?

• Beach nourishment - sand is manually replaced on beaches where it has been eroded. The transported sand has to come from another beach, it is expensive, it is temporary, and it generally replaces eroded sand with sand that is different in size, shape, sorting, and composition. • Relocation - moving buildings. People do not always want to move and it is another expensive solution

List three examples of hard stabilization and describe what each is intended to do. How does each affect sand distribution on a beach?

• Jetty - built in pairs and run perpendicular to the shoreline at the entrance to rivers and harbors. They are intended to prevent deposition in the river channels. They cause sand to accumulate on the side from which the longshore current is coming and to erode on the other side. • Breakwater - built parallel to the shoreline with the intent of protecting boats from the force of breaking waves. Sand may accumulate behind a breakwater close to the shore. • Seawall - designed to protect structures and property on the coast from breaking waves. The beach on the seaward side of the seawall will generally experience significant sand erosion.

Name the five subtropical gyres( ocean currents) and identify the main surface currents in each.

• North Atlantic Gyre - Gulf Stream, North Atlantic Drift, Canary Current, and North Equatorial Current. • South Atlantic Gyre - Brazil Current, South Equatorial Current, and Benguela Current. • North Pacific Gyre - California Current, North Equatorial Current, Kuroshito Current, and North Pacific Current. • South Pacific Gyre - South Equatorial Current, Peru Current, West Wind Drift, and East Australian Current. • Indian Ocean Gyre - South Equatorial Current, Agulhas Current, West Wind Drift, and West Australian Current.