Questions and Answers
What percentage of the Earth's surface is covered by the ocean?
What is a passive continental margin?
A passive continental margin occurs in the interior of a plate, far away from any plate boundary.
What is an active continental margin?
Continental convergent margins where the margin of the continent coincides with a convergent plate boundary.
What does salinity measure?
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What is thermohaline circulation?
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Continental shelf is underlain by ________ crust.
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The wave base is effective at moving water to a depth equal to half of the ________.
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How does a tombolo form?
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What causes eustatic sea level changes?
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What is a spit?
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What are marine terraces?
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Describe how longshore current operates along a coast.
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Study Notes
Ocean Coverage
- The ocean covers approximately 71% of Earth's surface.
Oceanic Structures
- Various ocean features include the Continental Shelf, Slope, and Rise, Abyssal Plains, Oceanic Ridges, and Oceanic Trenches.
Passive Continental Margins
- Found in the interior of tectonic plates, far from plate boundaries; examples include the Atlantic coasts of North and South America, Europe, and Africa.
- No current deformation occurs, as these margins result from the rifting of larger ancient continents.
Active Continental Margins
- These margins coincide with convergent plate boundaries.
- Notable current locations include the Pacific coast of South America and the Cascade Mountains in the U.S.
Salinity
- Salinity measures the concentration of dissolved ions in the ocean, ranging from 33 to 37 parts per thousand.
Thermohaline Circulation
- Seawater circulates vertically due to density changes driven by variations in salinity and temperature.
Key Geographical Definitions
- Continental Shelf: Underlain by thinning continental crust.
- Continental Slope: Transitional zone between continental and oceanic crust; leads to abyssal plains.
- Abyssal Plain: Vast, flat areas of the ocean floor, underlain by mafic oceanic crust.
- Passive Continental Margin: Tectonically stable areas away from plate boundaries.
- Active Continental Margin: Dynamic areas where continental edges converge with tectonic plates.
- Wave Base: Depth at which wave motion effectively stops, at half the wavelength.
- Wave Refraction: Waves bend as they approach the shoreline due to varying bottom depth.
- Spit: Elongated sand/gravel deposit extending into open water, commonly formed at bay mouths.
- Tombolo: A spit connecting the mainland to an island.
- Fjord: Deep, U-shaped valleys flooded by sea, created by glacial activity.
- Atoll: Circular coral reefs remnants surrounding submerged volcanic islands.
- Estuary: Flooded river valleys where freshwater and saltwater mix.
Longshore Current and Beach Drift
- Coastal structures like sea walls and groins can alter sediment movement, influencing longshore currents and beach drift, sometimes causing erosion down-current.
Features of Rocky Coasts
- Wave Cut Benches: Elevated areas formed by the uplifting of wave cut benches on emergent coasts.
- Wave-Cut Cliffs: Formed due to erosion and resistance, often leading to marine terraces.
- Marine Terraces: Elevated wave-cut benches that have survived above sea level.
- Sea Caves: Created by differential erosion; may develop into sea arches if two caves meet.
- Sea Arches: Formed when sea caves erode enough to connect, eventually collapsing into sea stacks.
- Sea Stacks: Isolated columns of rock remaining after sea arches collapse.
Eustatic Sea Level Changes
- Fluctuations in sea level are driven by climate changes affecting ocean water volume.
- During glacial periods, sea levels drop as water is trapped in ice; during interglacial periods, melting ice raises sea levels.
- Higher ocean temperatures can expand water volume, contributing to sea level rise.
- Geographic transformations, such as volcanic activity, can also change sea levels through altering ocean floor shapes.
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Description
Explore these flashcards to learn about the ocean's coverage, its geological features, and the characteristics of passive continental margins. This quiz is designed to enhance your understanding of ocean geography and related terms. Perfect for geography students and enthusiasts.
