Currents and Tides Flashcards
How would you define a current?
The permanent or seasonal movement of surface water in seas and oceans.
What are the three types of currents?
Littoral drift (longshore currents), rip currents, and upwelling.
What occurs in littoral drift?
Occurs as waves do not hit the coastline perpendicular, generating a flow of water running parallel to the shoreline. This also results in longshore drift.
What are rip currents?
Strong currents moving away from the shoreline, developed when seawater is piled up by incoming waves.
What is upwelling?
Movement of cold water from deep in the ocean towards the surface, the more dense water replaces warmer surface water, creating nutrient rich cold ocean currents. These contribute to global ocean circulation currents.
What is a tide?
Periodic rise and fall in sea level.
What are tides caused by?
Gravitational pull from the sun, and mainly the moon (because it is nearer).
How does the moon influence tides?
Pulls water towards it, creating a high tide, and causing a compensatory bulge on the opposite side of earth.
What’s the highest monthly tidal range called?
Spring tide.
What’s the lowest monthly tidal range called?
Neap tide.
What direction are the moon and sun in during spring tides?
In a straight line respective to the earth.
What direction are the moon and sun in during neap tides?
Perpendicular to each other at a 90 degree angle.
(Results in 10-30% lower tides than average)
What is tidal range?
The difference in height of the sea water at high and low tide.
(This is not fixed)
What does tidal range determine?
Upper and lower limits of erosion and deposition.
Amount of time a day that the littoral zone is exposed to sub-aerial weathering.
What is a tidal/storm surge?
Occasions when meteorological conditions give rise to strong winds which can produce much higher water levels than those at high tide.
