Oceans Review

Oceanography Study Guide

Ocean Zones

• Mixed Layer Zone (0-250m): The warmest ocean layer with the most sunlight. This zone supports the highest concentration of phytoplankton, crucial for marine ecosystems.

• Thermocline Zone (250-1000m): A transition layer where temperature decreases rapidly from about 22°C at the top to 6°C at the bottom. Sunlight fades significantly in this zone.

• Deep Water Zone (1000m and deeper): The coldest and darkest layer, with temperatures ranging from 6°C to 2°C. No sunlight reaches this zone.

Ocean Topography

• Continental Slope: The steep edge of a continental landmass where upwelling commonly occurs.

• Seamounts: Underwater volcanic mountains that have not reached the ocean surface.

• Abyssal Plain: A flat and deep region of the ocean floor, largely featureless and covered in sediment.

• Mid-Ocean Ridge: A chain of volcanic mountains formed by divergent tectonic plates.

• Volcanic Islands: Islands formed from volcanic activity, typically at convergent subduction zones or over hot spots.

• Continental Shelf: The shallow, submerged extension of a continent.

• Trench: A deep ocean depression formed at convergent subduction boundaries, marking the deepest parts of the ocean.

Seafloor Spreading

• Occurs at divergent plate boundaries, where magma rises to create new oceanic crust.

• Older oceanic crust is found farther from the mid-ocean ridge.

• The process records Earth’s magnetic field reversals in seafloor rock.

Salinity

• Typical ocean salinity ranges from 33-37 ppt (parts per thousand).

• Primary sources of oceanic salts include volcanic eruptions and river runoff.

• Dominant components: sodium (Na+) and chloride (Cl-), forming sodium chloride (NaCl), or table salt.

Ocean Currents

1. Surface Currents: Driven by global winds; warm currents transport heat from the equator to the poles, while cold currents move from the poles toward the equator.

2. Deep Ocean Currents: Driven by density differences due to variations in temperature and salinity.

3. Thermohaline Circulation: Also called the Global Conveyor Belt, this system links surface and deep currents worldwide.

Upwelling

• Occurs when deep, cold, nutrient-rich water rises to the surface.

• Enhances marine life, supporting phytoplankton and fish populations.

El Niño & La Niña

• El Niño: An irregular climate event that warms the Pacific Ocean, disrupts weather patterns, and halts upwelling near South America.

• La Niña: The opposite of El Niño, it strengthens trade winds, increases upwelling, and brings colder ocean temperatures.

Land & Sea Breezes

• Sea Breeze (Daytime): Land heats faster than the ocean, causing warm air to rise over land and cooler ocean air to move in.

• Land Breeze (Nighttime): Land cools faster than the ocean, warm air rises over the ocean, and cooler air from land moves out to sea.

Practice Test (40 Questions)

1. What is the primary function of the Mixed Layer Zone?

2. What depth does the Thermocline Zone begin at?

3. Which ocean zone receives no sunlight?

4. What geological feature forms at divergent boundaries?

5. What is the name of the deepest part of the ocean?

6. What is the main force driving surface currents?

7. What is the driving factor behind deep ocean currents?

8. What is another name for Thermohaline Circulation?

9. What ocean process brings nutrient-rich water to the surface?

10. How does El Niño affect upwelling?

11. How does evaporation impact salinity levels?

12. What are the two primary components of ocean salt?

13. How does La Niña influence upwelling?

14. Where does water sink in the Thermohaline Circulation?

15. How does the specific heat of water compare to land?

16. What causes a sea breeze to form?

17. What is the mechanism behind a land breeze?

18. Why is older ocean floor found further from mid-ocean ridges?

19. What is the flattest region of the deep ocean floor?

20. Define a seamount.

21. How do volcanic islands form?

22. Where do deep-sea trenches form?

23. What is the process by which new oceanic crust is created?

24. How frequently does El Niño occur?

25. What type of plate boundary generates mid-ocean ridges?

26. Why is upwelling important for marine ecosystems?

27. How does El Niño impact global weather patterns?

28. What role do trade winds play in El Niño and La Niña events?

29. Which ocean layer contains the most phytoplankton?

30. How does salinity affect ocean density?

31. What is the typical range of ocean salinity?

32. Compare the density of cold and warm water.

33. What are the primary sources of oceanic salts?

34. How does land temperature change compared to ocean temperature?

35. What happens to atmospheric pressure over warm land?

36. What separates continental crust from oceanic crust?

37. How do mid-ocean ridges provide evidence for plate tectonics?

38. Why do ocean floor rocks display magnetic reversals?

39. What happens when warm water replaces cold water during El Niño?

40. Why does upwelling cease during El Niño?