Questions and Answers
The rest of the wave water is deflected ___ to the shoreline to form the longshore current.
parallel
What is the movement of sediment or surfers within the surf zone called?
Longshore transport
Surf zone is the turbulent water between the ___ zone and the ___ zone.
breaker, swash
___ is the ocean current which flows from the shoreline out past the breaking waves.
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What is a jetty?
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What is the purpose of a dredge?
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The grain size at Surfside Beach is (large/small), and (well/poorly) sorted compared to that at Alamitos Bay.
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Source rock for the terrigenous components of Surfside Beach is ___.
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When a wave reaches a beach or coastline, it releases a burst of ___ that generates a longshore current.
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What problem did the Beach Replenishment Project address?
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Jetties promote beach erosion at Surfside Beach.
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A seawall could provide a solution to the problem of beach erosion by stopping the natural ___ of sand by the waves.
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The California Continental Borderland is characterized by a number of ___ that are collecting ___ sediments eroding from the continent and islands.
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What is the main geological activity affecting the Borderland?
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The ___ connects points of equal elevation (on land) or depth (on ocean floor).
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What is a profile view?
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An ocean basin is a relatively deep part of the ocean floor surrounded by ___ ocean floor.
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Submarine fans are large fan-shaped ___ of sediments composed of ___ delivered from the end of a ___.
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Course terrigenous sediment, typical of very shallow water, can be deposited on a ___ because ___ can carry shallow water sediment down through a ___ and eventually deposit it into deeper water.
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The San Clemente Island to Manhattan Beach portion of the Continental Borderland shows deep, wide ___ bounded by ___.
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The Catalina Basin is filling with sediment at a much slower rate than the San Pedro basin because the San Pedro basin is (______/farther from) the continents.
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The continental borderland has formed over the past 19 years by the movement of the ___ and the ___.
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As wind flows across the surface of the ocean, it drags some of the ___ along with it.
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The Coriolis effect causes deflection of currents to the (______/left) in the northern hemisphere.
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What is an eddy in the ocean?
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Seasonal changes affect the flow of the Southern California Countercurrent because the strongest ___ winds are found during spring.
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Higher winds lead to stronger waves that cause it to ___, inhibiting the SAR from picking it up.
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A beach grows ___ when small waves wash sediment ashore.
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A wave base is the ___ to which an ocean wave will disturb water molecules as the wave passes through.
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Study Notes
Longshore Current and Transport
- Longshore current flows parallel to the shoreline, formed by waves breaking at an angle, with some water moving up the beach face in the swash zone.
- Larger waves release more energy, resulting in faster longshore currents.
- Longshore transport refers to the movement of sediment within the surf zone.
Surf Zone Dynamics
- The surf zone is the turbulent water region between the breaker zone and the swash zone, where longshore currents primarily flow.
- Rip currents are ocean currents moving from the shore out past breaking waves, often formed by specific beach shapes.
Coastal Structures and Erosion
- Jetties are human-made structures designed to protect harbor entrances from wave erosion.
- Dredges vacuum sediment from the ocean floor and deposit it onshore.
Sediment Composition and Sources
- Surfside Beach features large, poorly sorted grains of feldspar, quartz, and magnetite.
- Local mountains are the source of terrigenous sediment, while biogenous components originate from the ocean.
Wave Energy and Longshore Currents
- Wave energy generates longshore currents, affecting their velocity based on the wave’s angle, slope of the beach, and height—steeper and higher waves increase velocity.
- Longshore currents are typically faster in winter due to larger waves.
Beach Replenishment and Erosion
- The Beach Replenishment Project was initiated when Surfside Beach faced severe erosion threatening homes, with future replenishments necessary due to smaller sediment grain sizes that erode quickly.
- Seawalls can prevent sand movement but may exacerbate erosion by reflecting waves back to the ocean.
California Continental Borderland Features
- The Borderland contains basins that collect terrigenous and biogenous sediments, characterized by steep slopes known as escarpments.
- Major tectonic movements along the San Andreas Fault have shaped these features, leading to fractured and folded crustal fragments.
Ocean Basin and Sediment Dynamics
- Ocean basins are deep parts of the ocean floor surrounded by shallower areas, gradually filling with sediment.
- Submarine fans form from sediments carried from submarine canyons, shaped by turbidites.
Ocean Currents and Wind Interaction
- Wind-induced currents flow at about 2-5% of wind speed, with currents generally moving 45 degrees to the wind direction due to the Coriolis effect.
- Gyres are large circular currents formed by the interaction of prevailing winds, gravity, and the Coriolis effect.
Seasonal Effects on Ocean Currents
- Seasonal wind changes affect the Southern California Countercurrent, which accelerates during the summer and impedes during spring as the Countercurrent moves closer to shore.
Imaging and Eddy Flow
- Synthetic Aperture Radar (SAR) imaging is better for analyzing small eddies compared to sea surface temperature (SST) imaging due to its higher spatial resolution and less limitation by cloud cover.
- Wind-generated waves can obstruct SAR imaging by causing eddy flow to scatter.
Beach Dynamics and Wave Interaction
- Beaches are dynamic environments, widening with small waves and shrinking due to larger waves that remove sediment.
- The wave base is the depth at which wave action only disturbs water molecules; deep-ocean waves do not touch the ocean floor, while shallow-water waves do, impacting sediment movement.
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Description
Test your knowledge with these oceanography flashcards focused on longshore currents. Understand how waves interact with shorelines and the dynamics of near-shore ocean water flow. Ideal for students looking to reinforce their grasp of key concepts in oceanography.
