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

Tides

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

Galveston Tide Table

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

Spring and Neap Tides Diagram

http://csep10.phys.utk.edu/astr161/lect/time/tides.html

Waves

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

Currents

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 Major World Currents

http://media-2.web.britannica.com/eb-media/57/70057-004-85830DA6.gif

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