Marine Science I Honors - Tides

Vocabulary flashcards about tides, lunar influence, and related concepts.

Tides

Result from the gravitational pull of the moon and, to a lesser degree, the sun.

Tides

Very long-period waves that originate in the ocean and progress toward the coastlines where they appear as the regular rise and fall of the sea surface.

Equilibrium Theory

Proposed by Isaac Newton as an explanation for the tides, assuming a perfectly uniform Earth, very deep water, and no landmasses.

Dynamic Theory

Modified Newton’s model to account for tidal variations; it shows there are several tidal bulges, not just two.

High Tide

Occurs when the highest part of the tide (crest) reaches the coast.

Low Tide

Occurs when the lowest part of the wave, or its trough, reaches the coast.

Tidal Range

The difference in height between the high tide and the low tide.

Tidal Current

The horizontal movement of water that accompanies the rising and falling of the tide.

Flood Current

The incoming tide along the coast and into bays and estuaries.

Ebb Current

The outgoing tidal current.

Slack Current

The outflow of a tide.

Spring Tides

Highest and lowest tides that occur when the sun and moon are aligned on the same or opposite sides of the Earth (new or full moon).

Neap Tides

Weaker tides that occur when the moon is in a quarter moon phase, and the sun and moon are at a right angle to the Earth.

Declination of Moon

The angle of the Moon’s orbit with respect to the Earth’s equator.

Perihelion

Earth’s closest approach to the Sun.

Aphelion

Earth’s farthest distance from the Sun.

Perigee

Moon’s closest approach to the Earth.

Apogee

Moon’s farthest distance from the Earth.

Super Moon

When the Moon is at perigee, it appears ~14% larger when viewed from Earth.

King Tide

Common term to describe extra large high tides that occur when the Earth, Moon, and Sun are aligned at perigee and perihelion.

Underwater bathymetry

Shape of the seafloor

Diurnal Tide

Having a single low and high tide daily

Semidiurnal Tide

Having two roughly equal high and low tides daily.

Mixed Tide

Having two unequal high and low tides daily.

Tidal Bore

Forms when the incoming tide produces a wave that flows into a river or other narrow area.

Amphidromic points

Points where the water doesn’t rise and fall with the tides.

Tide Gauge

A device for measuring the change in sea level relative to a baseline such as mean sea level.