Oceanography Final
1. Define the following terms: wave height, wavelength, wave speed, and wave steepness.
Wave height: The vertical distance between the crest and the trough of a wave.
Wavelength: The horizontal distance between two successive crests or troughs.
Wave speed: The distance a wave crest travels per unit time.
Wave steepness: The ratio of wave height to wavelength.
2. Calculate wavelength and frequency given wave speed (4 m/min) and wave period (12 s).
F = 1 / 12 = 0.083 Hz
W=4 m/min60 s/min=0.067m/s 12s=0.804m
3. Determine speed of a deep-water wave with 200 m wavelength.
Identify wave speed from the provided graph using wavelength data.
4. Calculate wave height from constructive interference of Sea A (1.5 m) and Sea B (3.5 m).
Resultant wave height: 1.5m + 3.5m = 5.0 m
5. Describe what happens to deep-water waves in shallow water.
As a deep-water wave enters shallow water, it slows down due to seabed friction, its wavelength shortens, and its height increases as energy is compressed. The wave steepens until it becomes unstable, breaking when its height-to-wavelength ratio exceeds 1:7. This process releases energy, forming the breaking waves seen near shorelines.
6. Explain tsunami generation and characteristics.
Generation: Tsunamis are typically caused by large-scale underwater disturbances, such as earthquakes along subduction zones, volcanic eruptions, underwater landslides, or meteorite impacts. These events displace massive amounts of water, creating waves that propagate across oceans.
Characteristics:
Wavelength: Tsunamis have extremely long wavelengths, often exceeding 100 kilometers.
Wave speed: They travel quickly in deep water, up to 500–900 km/h, due to their dependence on water depth.
Behavior: Tsunamis behave as shallow-water waves because their wavelengths are much longer than ocean depth. In shallow water, the wave's height increases significantly, leading to destructive surges.
Shoreline appearance during the trough: When the trough of a tsunami arrives first, it causes a dramatic withdrawal of water from the shore, exposing the seabed and alarming coastal observers. This phenomenon is often a precursor to the devastating wave crest.
7. Why is the Sun's tidal influence only 46% of the Moon's?
The Sun's greater distance reduces its gravitational effect compared to the Moon's proximity.
8. How many spring tides occur in one lunar orbit, and how does the Moon appear?
Spring tides: Two (new moon and full moon).
Appearance: New moon is invisible; full moon is fully illuminated.
9. Contrast spring tides and neap tides.
Spring tides: Larger tidal range due to Sun-Moon alignment.
Neap tides: Smaller tidal range when Sun-Moon form a right angle.
10. Define longshore drift and its relation to longshore currents.
Longshore drift refers to the movement of sediment (like sand) along the coastline, driven by waves that strike the shore at an angle. As waves wash up and retreat, they move particles diagonally up the beach and then back down perpendicularly, creating a zigzag motion of sediment transport.
Longshore current is the water current flowing parallel to the shoreline, caused by the same angled wave action. The longshore current drives the longshore drift, influencing coastal erosion, deposition, and the shape of beaches.
11. Describe how barrier islands respond to rising sea levels and why some have peat deposits.
Response to Rising Sea Levels: Barrier islands migrate landward & upward through processes like overwash (waves depositing sand inland) and longshore drift (sediment transport along the shore). This helps them maintain their elevation relative to the rising sea level.
Peat Deposits: Peat forms in marshes behind the island from accumulated plant material. As the island shifts landward, sand from overwash buries these deposits, creating a record of past marsh locations.
This movement allows barrier islands to adapt to changing sea levels.
12. Distinguish between emerging and submerging shorelines.
Emerging shoreline: Raised by tectonic activity or sea level drop.
Submerging shoreline: Flooded by rising sea levels or land subsidence.
13. Describe types of hard stabilization, their purposes, drawbacks, and alternatives.
Seawalls
Purpose: Built parallel to the shoreline to protect coastal areas, infrastructure, and properties from wave erosion and storm surges.
Drawbacks: Seawalls reflect wave energy, which can cause scouring and increased erosion at their base. Over time, they may fail and require costly maintenance.
Alternative: Beach nourishment, where sand is added to eroding beaches, providing a buffer against wave action while maintaining the natural landscape.
Groins
Purpose: Structures extending perpendicular to the shore, designed to trap sand moving along the coast via longshore drift, stabilizing beach areas.
Drawbacks: Groins disrupt sediment flow, leading to erosion on downdrift beaches. They can also alter natural coastal dynamics.
Alternative: Sand bypass systems that actively redistribute sand to downdrift areas, maintaining sediment balance without disrupting natural flow.
3. Breakwaters
Purpose: Offshore structures that reduce wave energy before it reaches the coast, protecting harbors, anchorages, and shoreline developments.
Drawbacks: Breakwaters can disrupt water circulation, leading to sediment accumulation and changes in nearby ecosystems. They are also expensive to build and maintain.
Alternative: Living shorelines, which use natural features like oyster reefs or vegetation to dissipate wave energy while enhancing habitat.
4. Jetties
Purpose: Built at the mouths of rivers or harbors to prevent sediment deposition and maintain navigable waterways.
Drawbacks: Like groins, jetties can disrupt longshore drift, causing erosion in adjacent coastal areas and altering sediment distribution.
Alternative: Dredging, where sediment is periodically removed to maintain channel depth without permanently altering coastal processes.
14. Distinguish between estuaries, lagoons, and marginal seas with examples.
Estuary: River meets ocean (e.g., Chesapeake Bay).
Lagoon: Shallow water behind barrier islands (e.g., Venice Lagoon).
Marginal sea: Semi-enclosed by land (e.g., Mediterranean Sea).
Estuaries
Definition: Partially enclosed coastal areas where freshwater from rivers meets and mixes with saltwater from the ocean.
Formation: Typically formed by rising sea levels flooding river valleys, tectonic activity, or sandbar development.
Example: Chesapeake Bay in the United States.
Key Characteristics: Estuaries have variable salinity levels, nutrient-rich waters, and high biological productivity, making them critical habitats for marine life.
Lagoons
Definition: Shallow, coastal bodies of water separated from the ocean by sandbars, barrier islands, or reefs.
Formation: Created by wave and current action that deposits sediment along the coast, forming a barrier.
Example: Venice Lagoon in Italy.
Key Characteristics: Lagoons are typically brackish or saline and have limited water exchange with the ocean. They are often calm and support unique ecosystems.
Marginal Seas
Definition: Large, semi-enclosed bodies of saltwater that are connected to the ocean but partly surrounded by land.
Formation: Result from tectonic activity, continental drift, or the isolation of ocean basins.
Example: Mediterranean Sea.
Key Characteristics: Marginal seas are influenced by ocean currents and regional climates. They often have unique salinity and temperature patterns compared to the open ocean.
15. List and describe the four types of estuaries based on origin, with examples.
Coastal Plain Estuaries
Formation: Created when rising sea levels flood river valleys. This typically occurs during interglacial periods when ice caps melt.
Example: Chesapeake Bay in the United States.
Key Characteristics: These estuaries have broad, shallow basins with gently sloping sides and a mix of salt and freshwater that gradually blends over distance.
Tectonic Estuaries
Formation: Result from land subsidence or sinking due to tectonic activity, often along fault lines.
Example: San Francisco Bay in California.
Key Characteristics: These estuaries often have irregular shapes due to tectonic movements and may include deep areas where land has sunk significantly.
Bar-Built Estuaries
Formation: Formed when sandbars or barrier islands accumulate along the coastline, trapping freshwater behind them.
Example: Pamlico Sound in North Carolina.
Key Characteristics: These estuaries are typically shallow and narrow, with limited water exchange between the lagoon and the ocean, resulting in distinct salinity patterns.
Fjord Estuaries
Formation: Carved by glacial activity during ice ages, fjords are deep, steep-sided valleys that fill with seawater after glaciers retreat.
Example: Norwegian Fjords.
Key Characteristics: These estuaries are deep and narrow, with a shallow sill at the mouth, which restricts water flow and creates distinct water layers (stratification).
16. Why is oil considered one of the least damaging marine pollutants?
Oil disperses and degrades relatively quickly compared to persistent pollutants.
17. What properties make plastics both useful and harmful in marine environments?
Useful: Durable, lightweight, and resistant to degradation.
Harmful: Persistence in the environment, leading to long-term pollution.
18. Distinguish between plankton, nekton, and benthos, with examples.
Plankton: Drifting organisms (e.g., phytoplankton).
Nekton: Active swimmers (e.g., fish).
Benthos: Bottom dwellers (e.g., crabs).
19. Define a living organism.
An entity that exhibits metabolism, growth, reproduction, response to stimuli, and homeostasis.
20. Compare warm-water and cold-water marine species in lifespan, size, and abundance.
Warm-water species: Shorter lifespan, smaller size, higher abundance.
Cold-water species: Longer lifespan, larger size, lower abundance.
21. Provide examples of positive and negative feedback loops.
Positive feedback: Melting ice reduces albedo, accelerating warming.
Negative feedback: Increased CO₂ boosts plant growth, reducing CO₂ levels.
22. List and define the five components of Earth's climate system.
Atmosphere: The gaseous envelope surrounding Earth, controlling weather and climate through its composition (e.g., CO₂, water vapor).
Hydrosphere: Includes all water on Earth, such as oceans, lakes, and rivers, playing a major role in heat distribution via currents.
Cryosphere: Ice and snow, which reflect solar radiation and influence sea levels.
Lithosphere: The solid Earth's surface, including mountains, which affect atmospheric patterns and ocean currents.
Biosphere: All living organisms, interacting with and influencing other climate system components through processes like photosynthesis and respiration
23. What are proxy data?
Indirect evidence used to infer past climate conditions (e.g., ice cores, tree rings).
24. Provide two examples of proxy data and their environmental significance.
Ice Cores: Layers of ice trap ancient air bubbles and stable isotopes, providing records of past greenhouse gas levels and temperatures.
Environmental Significance: Ice cores reveal the relationship between CO₂ concentrations and temperature over the past 800,000 years, highlighting natural climate variability.
Tree Rings: Ring width and isotopic composition indicate growth conditions, reflecting temperature, rainfall, and CO₂ levels.
Environmental Significance: Tree rings help reconstruct regional climate patterns, such as droughts and cooling events caused by volcanic eruptions, offering insights into climate variability.