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Questions and Answers
What determines the vertical distance measured as wave height?
Which of the following best describes wave base?
How does wave amplitude relate to wave height?
What factors influence the energy imparted to water and the resultant wave formation?
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What is the impact of storms like hurricanes on wave characteristics?
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What process describes the sorting of wavelengths in a wave train as it travels to the shore?
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Which zone overlaps with the surf zone and experiences periodic wet and dry conditions from waves and tides?
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What phenomenon occurs when crests align with other crests, resulting in increased wave height?
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During what condition do tsunamis generally go unnoticed in the open ocean?
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What is the effect of wave refraction as waves approach the shoreline?
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What causes longshore drift to transport sand along the coastline?
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Which of the following statements accurately describes emergent coasts?
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What is the primary method that communities use to mitigate the formation of spits and baymouth bars?
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What primarily distinguishes rip currents from undertow?
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Which feature is commonly associated with submergent coasts?
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What is the primary function of jetties in coastal management?
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How do groins affect sediment movement along a beach?
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What geological feature typically indicates the presence of a submarine canyon?
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What is a common consequence of constructing breakwaters?
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How does the principle of uniformitarianism apply to ancient tidal flat deposits in the Big Cottonwood Formation?
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Study Notes
Waves and Wave Processes
- Wind transfers energy to water through friction, causing waves to form.
- Waves move as individual oscillating particles of water.
- The crest is the highest point, the trough is the lowest point.
- Wave height is the vertical distance between the crest and trough, determined by wave energy.
- Wave amplitude is half the wave height.
- Wavelength is the horizontal distance between consecutive crests.
- Wave velocity, the speed of a crest, is related to wave energy.
- Wave period is the time for adjacent crests to pass a point.
- Water particle motion diminishes with depth and is negligible at about half the wavelength.
- Wave base is the depth where water is no longer disturbed by waves, about half the wavelength.
- Waves approaching shore with crests 6 meters apart disturb water to 3 meters deep, known as fair-weather wave base.
- During storms, wavelength and wave base increase to a depth called storm wave base, about 91 meters.
- Wave generation depends on wind velocity and fetch, the distance across which the wind blows.
- Waves striking a shore are often generated by storms hundreds of miles away, traveling for days.
- A group of parallel waves traveling together is called a wave train.
- Wave trains can have various wavelengths, with longer wavelengths traveling faster and arriving at a distant shore first.
- This wavelength sorting process is called wave dispersion.
Behavior of Waves Approaching Shore
- On the open sea, waves appear choppy due to wave interference from different directions.
- Constructive interference occurs when crests align, amplifying wave height.
- Destructive interference occurs when crests align with troughs, canceling each other out.
- As waves approach shore and contact the seafloor, they slow down.
- However, wave energy remains the same, causing waves to build up higher.
- In shallow water, the wave crest may pour over the trough, forming a breaker.
- Tsunamis, sometimes called tidal waves, are generated by events like earthquakes, landslides, or volcanic eruptions affecting the seafloor.
- During earthquakes, crustal rock movement can abruptly elevate the seafloor, creating a tsunami.
- Tsunamis travel at speeds of over 322 kph, carrying enormous energy.
- Tsunamis may be unnoticed in the open ocean due to their speed, long wavelength, and low wave height.
- As tsunamis approach shore and interact with the shallow seafloor, friction increases, causing wave height to build up.
- The massive wave, called a tsunami runup, can be over 30 meters high, causing destruction far inland.
Shoreline Features
- Coastlines are dynamic and geologically complex, with erosional and depositional features.
- The shoreline is the interface between water and land, shifting with tides.
- This shifting interface is called the littoral zone.
- Waves, currents, climate, coastal morphology, and gravity all act on the shoreline.
Shoreline Zones
- Offshore zone is below water, active due to turbidity currents.
- Nearshore zone is the area affected by waves, extending to a depth of half the wavelength.
- Surf zone is where waves break.
- Foreshore zone overlaps the surf zone, periodically wet and dry due to waves and tides.
- Backshore zone is always above sea level, where dunes can form.
Refraction, Longshore Currents, and Longshore Drift
- Waves approaching the shoreline at an angle slow down first on the end nearest the beach, bending the wave crests, called wave refraction.
- Refraction causes waves to appear to approach the shoreline straight on.
- However, as refracted waves approach at a slight angle, they create a current called the longshore current.
- Waves stir up sand in the surf zone and move it along the shore, called longshore drift.
- Longshore drift moves sand north to south on both the east and west coasts of North America.
- Longshore drift can deposit sand in bays or inlets, forming spits.
- A spit extending across a bay mouth is called a baymouth bar.
- Jetties, long barriers, are built to deflect sand away from harbors.
- Dredging, the removal of sand, is another method to keep harbors open.
- Rip currents occur when wave trains push water directly towards the beach, causing water to flow back out to sea in narrow outlets.
- Undertow is a current that moves away from the shore beneath approaching waves, strongest in the surf zone.
Emergent and Submergent Coasts
- Emergent coasts occur where sea levels fall relative to land level.
- Submergent coasts occur where sea levels rise relative to land level.
- Features associated with emergent coasts:
- High cliffs
- Headlands
- Exposed bedrock
- Steep slopes
- Rocky shores
- Arches
- Stacks
- Tombolos
- Wave-cut platforms
- Wave notches
- Features associated with submergent coasts:
- Flooded river mouths
- Fjords
- Barrier islands
- Lagoons
- Estuaries
- Bays
- Tidal flats
- Tidal currents
Human Impact on Coastal Beaches
- Humans impact coastal beaches through construction and efforts to manage erosion.
- Jetties, groins, dams, and breakwaters are used to mitigate the effects of erosion and waves.
- Jetties divert currents and protect harbors and beaches.
- Groins are smaller structures built perpendicular to the shoreline, trapping sand on the upstream side.
- Dams trap sand, reducing sediment supply to beaches.
- Beach replenishment involves hauling in sand from other locations, potentially disrupting ecosystems.
- Breakwaters, offshore structures, create calm waters behind them but can interrupt longshore drift, leading to tombolo formation.
Submarine Canyons
- Submarine canyons are deep underwater canyons on continental shelves.
- They typically form at the mouths of major river systems.
- Turbidity currents, dense currents rich in sediment, can erode and deepen canyons, leading to fan-shaped deposits on the continental rise.
Currents and Tides
- Ocean currents are driven by global winds and water density.
Ocean Currents and Heat Distribution
- Ocean currents act as Earth's heat engine, transporting solar energy absorbed by ocean water.
- Water's high specific heat allows it to absorb significant heat with minimal temperature change.
- Oceans cover 71% of Earth’s surface, acting as a heat reservoir.
Surface Currents
- Earth's rotation and the Coriolis effect influence ocean currents.
- Large circular currents called gyres exist in the Atlantic, Pacific, and Indian Oceans.
- Gyres rotate clockwise in the northern hemisphere and counterclockwise in the southern hemisphere due to the Coriolis Effect.
- Western boundary currents transport warm water from the equator towards the poles, influencing local climates.
- Examples of western boundary currents include the Gulf Stream and the Kuroshio (northern hemisphere) and the Brazil, Mozambique, and Australian currents (southern hemisphere).
- Eastern boundary currents return cold water towards the equator, impacting the climate of adjacent land masses.
- The warm Gulf Stream moderates Northern Europe's climate, making it milder than similar latitudes in northeastern Canada and Greenland.
- The cool Humboldt Current (Peru Current) along South America's west coast limits evaporation, contributing to the aridity of the Atacama Desert in Chile.
Deep Currents
- Ocean current direction is determined by water density, influenced by temperature and salinity.
- Salinity is impacted by evaporation and freshwater influx from rivers.
- As western boundary currents cool at high latitudes, evaporation and ice formation increase salinity.
- Colder, saltier, and denser water sinks, forming deep-water currents.
- Deep-water movement is called thermohaline circulation, connecting the world's deep ocean waters.
- The Gulf Stream's movement exemplifies the beginning of thermohaline circulation.
- The global conveyor belt refers to the interconnected shallow and deep-ocean circulation, which mixes and overturns the entire world ocean, supplying nutrients to marine life.
Tides
- Tides are the daily rise and fall of sea level caused by the gravitational pull of the Sun and Moon.
- The Moon's gravitational influence on tides is more prominent due to its closer proximity to Earth.
- The tidal range—difference between high and low tide—is influenced by the Sun and Moon's positions relative to Earth.
- Spring tides occur during full or new moon phases when the Sun, Moon, and Earth align, resulting in maximum tidal range.
- Neap tides occur when the Moon and Sun are at right angles to Earth, resulting in minimal tidal range.
- Tides are measured at coastal locations and predictions are published by NOAA.
- Tidal patterns are categorized into three types:
- Diurnal: One complete cycle per tidal day (slightly longer than 24 hours).
- Semidiurnal: Two complete cycles per tidal day (approximately 12 hours and 50 minutes).
- Mixed: A combination of diurnal and semidiurnal patterns with varying amplitudes and highs and lows.
- Tidal patterns are influenced by bathymetry: ocean basin depths and continental obstacles.
- Tidal forecasts are typically made for only a few days in advance.
- The typical tidal range is approximately 1 meter (3 feet).
- Extreme tidal ranges occur in narrow, funnel-shaped areas like the English Channel (7-9.75 meters) and the Bay of Fundy (average 12 meters, extreme 18 meters).
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Description
Explore the fascinating concepts of waves and wave processes in this quiz. Learn about wave formation, characteristics such as crest and trough, and how energy is transferred in water. Test your understanding of wave height, amplitude, wavelength, and the impact of storms on waves.
