Podcast
Questions and Answers
How does the shape of an ocean basin influence tidal range?
How does the shape of an ocean basin influence tidal range?
- Wide and symmetrical basins develop miniature amphidromic systems, influencing tidal range. (correct)
- Narrow basins have larger tidal ranges due to the concentration of tidal energy.
- Basin shape has no influence on tidal range; tides are solely determined by gravitational forces.
- Tidal range is consistent across all ocean basins, regardless of shape.
Under what specific conditions does a tidal bore typically form?
Under what specific conditions does a tidal bore typically form?
- Along coastlines with minimal tidal variation.
- In deep ocean trenches far from coastal regions.
- In river inlets exposed to significant tidal fluctuations. (correct)
- In large, open bays with unobstructed water flow.
If a location experiences mixed tides, how is the zero tide level (tidal datum) typically determined?
If a location experiences mixed tides, how is the zero tide level (tidal datum) typically determined?
- It is set at the mean sea level, averaged over several years.
- It is the average level of all low tides (MLW).
- It is the average level of all high tides.
- It is based on the average level of the lower of the two daily low tides (MLLW). (correct)
How does the speed of a tidal bore compare to the theoretical speed of shallow-water waves?
How does the speed of a tidal bore compare to the theoretical speed of shallow-water waves?
Why are tidal bores considered less dangerous than other types of large waves, such as tsunamis?
Why are tidal bores considered less dangerous than other types of large waves, such as tsunamis?
Why did Newton consider his explanation of tides incomplete, despite understanding gravitational influences?
Why did Newton consider his explanation of tides incomplete, despite understanding gravitational influences?
In the context of tides, what is the primary reason the ocean surface does not reach a complete equilibrium position instantaneously?
In the context of tides, what is the primary reason the ocean surface does not reach a complete equilibrium position instantaneously?
What ocean depth would be required to support a tidal crest moving at 1,600 km/h, according to the equilibrium model?
What ocean depth would be required to support a tidal crest moving at 1,600 km/h, according to the equilibrium model?
How do landmasses primarily affect tidal movements as Earth turns?
How do landmasses primarily affect tidal movements as Earth turns?
What is the primary cause of mixed tidal patterns (or semidiurnal mixed tides)?
What is the primary cause of mixed tidal patterns (or semidiurnal mixed tides)?
What defines an amphidromic point in the context of tidal dynamics?
What defines an amphidromic point in the context of tidal dynamics?
How does the Coriolis effect influence tidal movement around amphidromic points?
How does the Coriolis effect influence tidal movement around amphidromic points?
What is a tidal datum primarily used for?
What is a tidal datum primarily used for?
Flashcards
Tidal Range
Tidal Range
The difference in height between high tide and low tide.
Equilibrium Model
Equilibrium Model
Theoretical model predicting tide behavior under ideal conditions without interference.
Dynamic Theory of Tides
Dynamic Theory of Tides
Explains tidal patterns considering dynamic interactions with landforms and ocean basin shape.
Tidal Patterns
Tidal Patterns
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Semidiurnal Tides
Semidiurnal Tides
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Amphidromic Points
Amphidromic Points
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Coriolis Effect
Coriolis Effect
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Tidal Datum
Tidal Datum
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Mean Lower Low Water (MLLW)
Mean Lower Low Water (MLLW)
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Mean Low Water (MLW)
Mean Low Water (MLW)
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Tidal Bore
Tidal Bore
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Study Notes
Newton's Incomplete Explanation of Tides
- Newton's theory of tides was incomplete, as the predicted tidal range (55cm for lunar, 24cm for solar) was significantly lower than the observed average (2 meters).
- The ocean surface doesn't reach equilibrium instantaneously, behaving as a wave.
- An equilibrium model suggests tides move at 1,600 km/h, requiring a much deeper ocean than the average depth (3.8 km). This highlights the limitations of the equilibrium model to accurately predict tides.
Dynamic Theory of Tides - Tidal Patterns
- Landmasses obstruct, divert, slow, and complicate tidal crest movement, leading to varied tidal patterns.
- Basin shape strongly influences tidal patterns and heights, causing rhythmic seiching (back-and-forth movement) in large basins.
- Tidal patterns include:
- Semidiurnal: two high and two low tides of nearly equal height daily.
- Diurnal: one high and one low tide daily.
- Mixed: successive high and low tides of varying heights created by a blend of diurnal and semidiurnal tides.
Dynamic Theory of Tides - Amphidromic Points
- Amphidromic points are no-tide points in ocean basins, where tidal crests and troughs cancel each other.
- Tidal crests rotate around amphidromic points, counter-clockwise in the Northern Hemisphere and clockwise in the Southern.
- Tide height increases with distance from amphidromic points; waves radiate outward toward distant shores.
- Colors on maps indicate tide extremes, with blue signifying least extreme tides.
Dynamic Theory of Tides - Tidal Datum
- A tidal datum is a reference level for comparing tidal heights, often represented as 0.0 on tide graphs.
- Datum isn't necessarily set at mean sea level (averaged height over years).
- For mixed tides, the datum is the average of the lower daily low tides (mean lower low water, MLLW).
- For diurnal and semidiurnal tides, the datum is the average of all low tides (mean low water, MLW).
Dynamic Theory of Tides - Ocean Basin Shape Influences
- Tidal range varies across ocean basins, influenced by basin configuration.
- Largest tidal ranges typically occur at the edges of large ocean basins.
- Wide, symmetrical basins develop miniature amphidromic systems, while narrow, restricted basins experience simpler in-and-out tide movements lacking complete amphidromic rotation.
Dynamic Theory of Tides - Tidal Bore/Tidal Waves
- Under ideal conditions, a tidal bore can form in river inlets with significant tidal fluctuations.
- A tidal bore is a steep wave moving upstream, generated by the tide crest in a river mouth.
- The river mouth confines the tide wave, causing it to move faster than the theoretical shallow-water wave speed for its depth.
- Tidal bores, despite their potential danger, are predictable.
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