Why does the ocean move? The tides, waves, and currents cause motion in the ocean They are the...
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Transcript of Why does the ocean move? The tides, waves, and currents cause motion in the ocean They are the...
Why does the ocean move?The tides, waves, and currents cause motion
in the oceanThey are the result of interactions of many
forces and factorsConditions in the Earth’s atmosphereThe movement of our planet in spaceThe Earth’s interactions with other bodies in
our solar system
TidesThe tide is the daily rise and fall of the ocean as
seen along the shoreThe highest elevation that the ocean reaches
along the shore is called HIGH TIDEThe lowest elevation that the ocean reaches
along the shore is called LOW TIDEThe vertical distance between low tides and high
tides is called the TIDAL RANGEThe tidal range varies depending on the shape and
depth of the coastlineThe number of islands in the Philippine archipelago
is rumored to vary depending on the tide
Time and tidesTide tables provide the times that low tide
and high tide occur in any given areaThe time between consecutive high tides and
low tides is approximately 6 hours and 20 minutes
This time may vary slightly from place to place depending on the types of coastline
Tide PatternsSEMIDIURNAL TIDE refers to a tide pattern that
has two highs and two lows each dayThe East Coast of the United States has this pattern
DIURNAL TIDE refers to a tide pattern that has only one high tide and one low tide each dayThe Gulf Coast of the United States has this pattern
MIXED TIDE refers to a tidal pattern with features of both semidiurnal and diurnal tidesThe West Coast of the United States has this patternThe first set of tides is stronger that the second set of
tides each day
Gravity and TidesTIDAL BULGE represents high tidesIt is caused by the moon’s gravity pulling on
the Earth
http://www.linz.govt.nz/hydro/tidal-info/tidal-intro/cause-nature/images/day1.gif
Types of TidesSpring Tides
Occur during the new moon and full moonThe highest and lowest tides result from the
combined pulling forces from the Earth, sun, and moon
Neap TidesWeaker tides in which the tides are not as high
or low as at other times of the month
WavesThey are up-and-down movements of the
ocean surfaceMostly caused by wind blowing on the
ocean’s surface
Factors that influence wavesWhen the wind blows, it pushes on the ocean
surface, causing the water to liftThe size and speed of a wave is dependent on
three factors:wind speed, the length of time it blows, and the distance over which it blows
The greater are the size and speed of the wave it generatesA gentle wind produces a small waveA strong wind produces a bigger wave
The Anatomy of a Wave
http://www.google.com/imgres?imgurl=http://www.geo.umn.edu/courses/1006/Fall00_night/sine.JPG&imgrefurl=http://www.geo.umn.edu/courses/1006/Fall00_night/Week10_11.html&h=289&w=721&sz=118&tbnid=uMzYk3dCWoEJ::&tbnh=56&tbnw=140&prev=/images%3Fq%3Danatomy%2Bof%2Ba%2Bwave%2Bdiagram&hl=en&usg=__qmk-MqjZs8a_eLZOX-VVRwL99_8=&sa=X&oi=image_result&resnum=2&ct=image&cd=1
Wave ActionA series of waves is called a WAVE TRAINThe speed (velocity) of a wave can be calculated
if the wavelength and period (the time it takes for one wave to pass a given point)are known
Formula:Velocity = wavelength/period
SWELLS are formed when waves extend beyond the windy area in which they are generatedThey have longer periods and more rounded crests
Types of WavesFormed when the top of the wave which moves
faster than its bottom pitches forward and crashes the water depth is less that one-half the wavelength
Whitecaps are formed in the open seas when winds blow off the tops of narrow crests
Rogue waves are formed when two or more large waves from a storm unite or when waves meet opposing currentsHuge waves with very high crests and low troughsRogue waves are dangerous and have caused the
loss of many ships at sea
TSUNAMISFirst recorded observation occurred on April
24, 1971An 84 m high wave struck a chain of islands
south of JapanInaccurately called tidal wavesAre not related to tides at allThey are generated by seismic activity
an undersea earthquakea landslide on the ocean floora volcanic eruption
CurrentsHighways of moving water that connect the
continentsMethod of delivery for messages in bottlesDriftwood from an offshore wreck washing
onto the shoreDefinition: a large mass of continuously
moving ocean water
The Coriolis EffectStates that the spinning Earth causes the
winds and surface waters to move in a clockwise direction in the northern hemisphere and in a counter clockwise direction in the southern hemisphere
The ocean currents move in giant circles called GYRES
Caused by the deflection of the ocean currents off of the continents
Wind-driven ocean currents are also called SURFACE CURRENTS
Vertical Ocean CurrentsSubsurface currentsCaused by temperature differences in the
ocean waterWarm water rises because its molecules are in
motion making it less denseCold ocean water is more dense so it sinksCONVECTION!!!!
Deep Ocean CurrentsCOUNTERCURRENTS
Warm water rises at the equator, flows until it cools, and then sinks at the poles
Slow horizontal ocean currents that flow in a direction generally opposite to the wind-driven currents at the surface
TURBIDITY CURRENTSFound along the continental slope where the seafloor
around the continent drops off steeplySpeed is due to the steepness of the slope
UPWELLINGSNutrients such as phosphates and nitrates are brought
up from the bottom of the ocean by vertical currents
Wave and Tide Induced Currents
UNDERTOWThe returning currents or backwash from a
wave breaking on shoreCan have enough force to cause someone
standing in the surf zone to fallRIP CURRENT
Fast, narrow current of water moving seawardCaused when the pressure from the water
accumulation on a sandbar forces it to break
Wave and Tide Induced Currents cont.TIDAL CURRENTS
Produced when the tide enters and leaves bays and inlets
Run parallel to shoreCarry nutrients and small organisms back and
forth between the bays and the offshore watersWHIRLPOOLS (aka eddies)
The rapid movement of surface waters in a circle
Usually happen between islandsOccur when tidal currents move past each
other in coastal waters or when ocean currents flow against tides or unusual coastal features