Beaches, shoreline processes, and coastal oceans Flashcards
Why is the coastal region constantly changing?
It changes due to waves and erosional deposition
How many people in the US live in coastal regions?
80 percent of people live in easy access of coast
What is Swash and Backwash?
Swash is the water that rushes up towards the shore and the backwash is the water that flows back into the ocean
How does the berm change with swash or backwash dominated zones?
The berm will be bigger and thicker if the area is swash dominated and the berm will be smaller and thinner if the area is backwash dominated
What are the different characteristics of a summer beach?
- swash dominates
- less energetic waves
- most of the swash seeps into the sand causing less backwash into the ocean.
What are the different characteristics of a winter beach?
- backwash domination
- high energy waves
- causes the beach to get saturated from the waves causing less soaking of the swash into the sand
- net erosion of the berm
How does a rip current form and what are its characteristics?
Forms when a narrow, fast moving section of water travels in an offshore direction. They can get as fast as 8 feet per second.
What type of wave movement leads to longshore current and longshore drift?
A zigzag movement of water near the shore
What is transported in longshore drift/longshore transport?
Long shore drift moves millions of tons of sediment along the coast regions.
Where do longshore currents occur?
They occur in the surf zone as the water is too deep if it is further off the shore
Where do longshore currents not occur?
they do not occur at depths greater than the wave base
What controls the amount of longshore drift at the coast?
They depend on the equilibrium between erosional and depositional forces.
What are examples of erosional shores?
Well-developed cliffs, in areas where tectonic uplift of the coast occurs. For example, the pacific coast.
What are some main features of erosional shores?
- Sea caves - which form at the base of cliffs
- Sea arches
- Sea stacks
What are examples of depositional shores?
Sand deposits and offshore islands are common. The shore is gradually subsiding. For example, the US southern coast and the gulf coast.
What are some main features of depositional shores?
Spit - Linear ridge of sediment in the direction of longshore drift
Bay Barrier - bar forms if the spit extends across the bay and joins the mainland
Tombolo - sand ridge that connects an island or sea stack to the main land
Barrier Islands - extremely long offshore deposits of sand parallel to the coast
what is a beach compartment and how does it function?
A beach compartment is a system that preserves a beach. The river provides sand and sediments, longshore currents distribute these sediments across the beach and submarine canyons help drain that sand away from the beach.
What is beach starvation?
A point where the draining of the sand into the ocean exceeds the amount of incoming sand, causing the beach to diminish.
What are some solutions to beach starvation?
- elimination of dams
- beach nourishment
What is hard stabilization? Pros and Cons?
A man made structure used to protect the coast. They help protect the coast, but are usually very expensive, easily destroyed and may alter the recreational coastline.
What is beach replinishment?
Artificial transport to beach to replace the lost sand. Usually very expensive and most of the sand comes from offshore areas, but they can also be taken from rivers, dams, and harbors.
Explain the difference in sea level changes due to crustal movement and eustatic changes in sea level.
The crustal movement results in changes of relative sea level as the land changes height and not the sea. Eustatic changes in sea level that occur over the whole Earth because of the changes in seawater volume or the ocean basin capacity.
Describe the two kinds of eustatic changes of sea level.
Changes in seawater volume: Formation or destruction of inland lakes and Ice ages.
Changes in ocean basin capacity: Seafloor spreading and the slow spreading mid Atlantic ridge displaces more water
How does climate change and warming affect sea level?
When the water is cooled, it contracts which lowers the sea level. when the water is warmed, it expands which increases the sea level.
Describe 4 types of estuaries by their geologic origin
Coast plain estuary - Former river valley now flooded with seawater
Fjord - Formed glaciated valley now flooded with seawater
Bar built estuary - Lagoon separated from ocean by sand bar or barrier island
Tectonic estuary - Faulted or folded down dropped area now flooded with ocean
What is a dead zone? How is it formed?
Deep water anoxic layer. forms as phytoplankton in the surface die and sink down into the salty water layer, they are decayed, which uses up all the oxygen.
Define the terms “wetlands”
Ecosystems where the water table is close to the surface.
Why are wetlands valuable?
Wetlands are home to an enormous assortment of plants and animals
- Nurseries for baby fish; winter protection: migration stopover
- Wetlands also soak up nutrients from terrestrial runoff
- “Natures Kidney”
- Wetlands also protect shorelines from erosion, hurricanes
