Unit 13: Oceans and Coastal Processes
The seafloor's own geography, the currents that move heat and water around the globe, and what waves, tides, and coastlines are actually doing.
6 topics · 18 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Ocean Basins and the Seafloor
- How it worksHow does a continental shelf, a continental slope, and the deep abyssal plain form the seafloor's shape moving away from shore?
- Going furtherWhat feature marks the deepest part of the seafloor, where one plate subducts beneath another?
- Ties togetherHow does the mid-ocean ridge system connect back to seafloor spreading and plate tectonics?
Your turn1 of 2
Maps of the seafloor reveal towering mid-ocean mountain ranges, deep trenches, and vast flat plains, just as varied as continental terrain. Why does the seafloor have its own mountain ranges, canyons, and plains, just like the continents do?Ocean Currents: Surface Circulation
- How it worksHow do wind, the Coriolis effect, and continents combine to steer surface ocean currents into great circular gyres?
- How it worksWalk me through the Gulf Stream carrying warm tropical water up the U.S. East Coast toward Europe.
- Common mistakeWhy doesn't an ocean current flow in a perfectly straight line in the exact direction the wind is blowing?
Your turn1 of 2
A message in a bottle dropped into the Gulf Stream off Florida reliably ends up washing ashore in Europe years later, following the same route ships have tracked for centuries. Why does a message in a bottle dropped in one ocean reliably wash up on a predictable coast years later?Deep Ocean Currents: Thermohaline Circulation
- How it worksHow do differences in temperature and salinity change water density enough to drive global thermohaline circulation?
- Going furtherWhat happens to the global conveyor belt if melting ice dilutes the salty water that's supposed to sink near the poles?
- Ties togetherHow does surface wind-driven circulation connect to deep thermohaline circulation into one global conveyor belt?
Your turn1 of 2
Near Antarctica, seawater grows both frigid and unusually salty as sea ice forms, leaving concentrated salt behind in the water that remains liquid. How do differences in temperature and salinity change water density enough to drive global thermohaline circulation?Waves: How They Form and Break
- How it worksHow does wind transferring energy to the water's surface build a wave that travels without the water itself moving forward?
- How it worksWalk me through a wave slowing down, growing taller, and finally toppling over as it reaches shallow water.
- Common mistakeWhy doesn't the water itself travel all the way across the ocean the way a wave appears to?
Your turn1 of 2
A series of waves has a period of 10 seconds between successive crests passing a fixed point, and the waves travel at 11 meters per second. What is the wavelength, in meters, using wavelength equals speed times period?Tides and the Moon's Pull
- How it worksHow does the Moon's gravity pulling harder on the near side of Earth than the far side create two tidal bulges?
- Worked exampleFind roughly how many hours pass between one high tide and the next high tide.
- Ties togetherHow does lining up the Sun and Moon's pull during a full or new moon create extra-high spring tides?
Your turn1 of 2
High tide occurs roughly every 12.348 hours as Earth rotates beneath the Moon's two tidal bulges. About how many high tides would occur in a 8 day period at that interval?Coastal Erosion and Deposition
- How it worksHow do waves hitting a beach at an angle push sand steadily along the shore through longshore drift?
- How it worksWalk me through wave energy carving a sea cliff, an arch, and finally a lone sea stack out of solid rock.
- Common mistakeWhy isn't a beach's sand supply a fixed amount that never moves or gets replaced?
Your turn1 of 2
Longshore drift moves sand along a beach at a rate of about 11 meters per year. Over 21 years, about how many meters has a patch of sand moved down the coast?