Podcast
Questions and Answers
What is the primary difference between a white smoker and a black smoker?
What is the primary difference between a white smoker and a black smoker?
Which of the following is NOT a characteristic of abyssal plains?
Which of the following is NOT a characteristic of abyssal plains?
What is the primary method used in satellite-based ocean mapping?
What is the primary method used in satellite-based ocean mapping?
What is the primary difference between active and passive continental margins?
What is the primary difference between active and passive continental margins?
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Which of the following is NOT a feature found on a continental margin?
Which of the following is NOT a feature found on a continental margin?
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What is the primary advantage of using echo soundings to map the seafloor?
What is the primary advantage of using echo soundings to map the seafloor?
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Which of the following ocean provinces is characterized by the presence of hydrothermal vents?
Which of the following ocean provinces is characterized by the presence of hydrothermal vents?
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What is the primary difference between a seamount and a guyot?
What is the primary difference between a seamount and a guyot?
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What is the primary source of information for creating a hypsographic curve?
What is the primary source of information for creating a hypsographic curve?
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Which of the following best describes the term 'fathom'?
Which of the following best describes the term 'fathom'?
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Study Notes
Ocean Mapping
- Methods used to map the seafloor have strengths and weaknesses.
- Three major ocean provinces and their subdivisions with key features are listed and described.
- Active and passive continental margins are contrasted, including differences in tectonic activity and sediment accumulation.
- Interplate features like seamounts and guyots and their formation are identified and described.
- The hypsographic curve is used to discuss the height of land, depth of the ocean, and the area of Earth covered by land and sea.
Early Ocean Mapping
- Early methods included nautical instruments and maps.
- Fathoms (feet) and meters are both used to measure depths.
HMS Challenger
- Conducted the first systematic ocean floor measurements in 1872.
- Stocked 144 miles of rope.
- Made 492 bottom soundings.
- Found that the deep ocean floor has relief.
Echo Soundings
- Echo sounders use sound waves to measure depth.
- Depth is calculated from the time it takes for the sound to travel to the seafloor and return.
- The formula to calculate depth is D = 1/2 * v * t.
GLORIA Side Scanning Sonar
- A geological instrument utilizing long-range inclined acoustic sensors.
- Measures the shape of the seafloor.
- Images from GLORIA provide data gaps, showing an incomplete survey of the seafloor.
Mapping from Space
- Satellite measurements are used to study sea floor features.
- Measurements of sea surface bulges caused by gravitational anomalies, are used to indirectly calculate bathymetry (sea depth and shape).
Comparing Bathymetric Maps
- Bathymetric maps illustrate seafloor topography.
- Comparing maps from various resources (ship v. satellite).
- Ship-based methods and satellite-based methods vary, and are compared.
Ocean Profiles
- Displays various topographic cross sections of different ocean areas (based on echo sounder data).
- Depicts the varied topography of ocean basins.
Ocean Provinces
- Shows different ocean provinces (Continental margins, ocean basins).
- Demonstrates the Mid-Atlantic Ridge, a submarine mountain range.
- Identifies the continental margin for both North and South America as well as Europe and Africa.
Continental Margin
- Continental margins include the shelf, shelf break, slope, and rise.
- A diagram illustrates these features in a cross-section.
Active and Passive Margins
- Active margins are located close to plate boundaries and exhibit tectonic activity.
- Passive margins are not close to plates boundaries and show little tectonic activity.
- Active margins have steeper slopes, less wide shelves, and trenches, while passive margins have gentler slopes and wider shelves.
Passive Margins
- Passive margins are not close to any plate boundaries.
- They have no major tectonic activity.
- East coast of the United States is an example of a passive margin.
Active Margins
- Active margins are located close to or on plate boundaries.
- These areas have variable tectonic activity like trenches (e.g., Mariana Trench).
- The Pacific Ring of Fire is an active region with numerous trenches and volcanoes.
Deep Ocean Basin: Abyssal Plains
- Abyssal plains extend from the base of continental rises.
- They are the deepest, flattest parts of the Earth.
- Fine particles settle, forming the flat surface.
- Well developed in the Atlantic and Indian Oceans.
Abyssal Hills and Seamounts
- Abyssal hills are small, gently sloping hills.
- Seamounts are large, isolated underwater volcanic mountains.
- Table mount or guyots are submerged volcanic mountains with flattened tops.
Mid-Ocean Ridges
- Mid-ocean ridges are underwater mountain ranges where seafloor spreading occurs.
- Show varying water depths across the mid-ocean ridge, indicating geological features and plate movement.
Mid-Ocean Ridges: Hydrothermal Vents
- Hydrothermal vents are openings in the seafloor where hot, mineral-rich water emerges.
- Vent activity is related to magma chambers.
White Smokers
- Release cooler water (30-350°C).
- Rich in barium, calcium, and silicon.
- Mineral precipitates create white "smokes".
Black Smokers
- Water temperatures exceed 350°C.
- Solutions exiting vents are acidic.
- Rich in hydrogen sulfide.
- Creates black precipitates, forming chimneys.
Hypsographic Curve
- Illustrates the percentage of Earth's surface covered by land and sea at various elevations and depths.
- Shows the average elevation of land and the average depth of the oceans.
- Shows how land and water are distributed across the planet.
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Description
Explore the various methods and historical milestones in ocean mapping, from early nautical instruments to advanced echo soundings. This quiz covers the strengths and weaknesses of different mapping techniques, interplate features, and significant expeditions like the HMS Challenger. Test your knowledge on the key concepts of ocean provinces and continental margins.
