Waves and Tides Marine Biology
Waves Wave size and direction are determined by the Wind speed Wind duration Fetch- the open area over which the wind blows
Waves below the surface
Causes of Tides The moon and the sun exert gravitational forces on the earth. Moon is most important The liquid on earth is attracted to those large masses- follows the mass Centrifigal force of the earth/sun system forces a mass of ocean water to move in the opposites direction When the sun and moon line up, the tides are highest and lowest. The earth continues to spin under the water.
Spring and Neap Tides Spring tides when the sun and the moon are aligned Creates the highest high tides and lowest low tides. Neap tides when they are not aligned. sun animation
Semidiurnal Tides two high tides and two low tides per day.
Diurnal Tides One high tide and one low tide per day
Mixed Tides One high/high tide and one low/low tide per day
Diurnal tide cycle experiences one high and one low tide every lunar day. Many areas in the Gulf of Mexico experience these types of tides. Semidiurnal tide cycle two high and two low tides of approximately equal size every lunar day. Many areas on the eastern coast of North America.
What do they look like? • Everything is compared to a zero tide- defined as the average of all the low tides. • Make sure that you know what time zone it is showing. • The tidal range is the difference between the high tide and the low tide. (don’t forget – signs) • homer tide chart
Influences on Tides Movement of the moon Movement of the sun Your latitude Depth of coastal waters Configuration of the shore: deep, shallow, rocky, sandy, bay, river, fjord, headlands, open shore, configuration of the shore north or south of you, time of year. Eg tide rip or overfall
Tidal Phenomena Bore Tide Incoming tide in a narrow way or river that forms a wave Accompanied by lots of turbulence and a audible roar. Turnagain Arm of Cook Inlet, Alaska. Up to 2 meters in height and traveling and 20 km/h. Brian's Bore Tide Video
Storm Surges Abnormal rise of water generated by a storm, over and above the predicted tide. Wind driven increase in water level and a small pressure effect. Responsible for Much damage. shallow vs steep
Crossing the Colombia Bar
Misnomer: Rip Tide A result of storms, not tides animation
Tsunami Triggered by earthquakes Very, very deep waves that pile up to huge heights on land Early warning depends upon seismic data and bouys on the open sea tsunami animation tsunami video