Opening Assignment What causes ocean currents? What causes tides?

Today’s Activity Today you will read the NOAA Ocean Explorer – Ocean Currents information sheet and answer the 10 questions. After everyone is finished we will watch a tutorial on Ocean currents. g/player/lesson08.htmlhttp://oceanexplorer.noaa.gov/edu/learnin g/player/lesson08.html

Opening Assignment 1.Differentiate between surface currents and deep ocean currents. 2.What is the Coriolis effect?

Motion in the Ocean Tides, Currents and Waves

Tides

What are tides? Rhythmic rise and fall of ocean waters

What causes tides? The gravitational force of the moon and the sun on Earth –A gravitational force is a force that large objects (earth, sun & moon) exert on smaller objects (people, water, etc.) –Because the moon is much closer to earth than the sun it exerts a much greater force on the tides The centrifugal force of the earth spinning on it’s axis

The Basics of Tides The Earth rotates on it’s own axis every 24 hours The moon rotates around the earth approx. every 28 days There are usually 2 high tides and 2 low tides each day

The Basics of Tides A tidal day is 24 hours and 50 minutes (the time it takes for the earth’s rotation)

Tidal bulge caused by gravitational force of the moon Tidal bulge caused by rotational force of the earth

The Basics of Tides Tidal Range –The difference between the heights of consecutive high and low tides –This is a measurement of distance NOT time

Spring Tides Period of greatest tidal range Occurs when the earth, sun and moon are in a straight line with each other (new and full moon) Highest highs and lowest lows

Neap Tides Period of smallest tidal range Occurs when the sun, earth and moon form a right angle (1 st and 3 rd quarters of the moon) Lowest highs and highest lows

Marigram Graph of the tides (time on x-axis, tidal height on y-axis) Allows you to see what type of tide occurs in a particular area

How do tides affect marine organisms? The area that is submerged at high tide and exposed at low tide is called the Intertidal Zone Organisms that live in the intertidal zone must be able to tolerate large changes in temperature, humidity and salinity

Let’s review Tides.. 1.What two forces cause tides? 2.How long is a tidal day? 3.What is a spring tide? When do spring tides occur? 4.List 2 challenges of organisms that live in the intertidal zone. 5.Graphs of tides are called ___________. 6.What is the tidal range? When is the tidal range the smallest?

Let’s review Tides.. 1.What two forces cause tides? Gravity from the Moon and Sun, and centrifugal force of the Earth spinning. 2.How long is a tidal day? 24 hours 50 min. 3.What is a spring tide? Largest tides that occur when the moon, Earth and Sun are lined up. 4.List 2 challenges of organisms that live in the intertidal zone. Changing water level and changing temperature. 5.Graphs of tides are called Marigram. 6.What is the tidal range? Difference between high and low tide. It is the smallest during Neap tides.

Tides LfLFBIhttps:// LfLFBI

What causes currents and waves? Wind!

So, first we need to understand wind. Winds are caused by heat energy from the sun Hot air rises (because it is less _____) and the surrounding air gets sucked in to replace the rising air, creating wind.

Coriolis Effect Wind does not travel straight towards the equator, but is deflected by the coriolis effect

Coriolis Effect Tendency of objects (that are traveling long distances over the Earth’s surface) to bend to the right in the northern hemisphere and to the left in the southern hemisphere

VERY IMPORTANT! Winds are named for the direction of origin –Ex. an east wind (is headed west)

Surface Currents Caused by winds pushing the surface of the water The coriolis effect deflects the direction of the current –45° to the right in the northern hemisphere –45° to the left in the southern hemisphere Currents are named for the direction they are traveling to –An eastern current is headed east

Major Surface Currents

Types of Currents

Gyres Large, circular current systems –Rotate clockwise in the northern hemisphere –Rotate counter clockwise in the southern hemisphere Warm currents on the western sides of gyres carry warm waters to the polar latitudes Cold currents on the eastern sides carry cold water to the tropics Gyres regulate the earth’s climate!!!

Longshore Currents Runs parallel to or along beach Formed when waves hit beach at an angle Causes mass movements of sand (which can cause beach erosion) –People try to stop them by building jetties out of rocks, wood or concrete –Doesn’t stop effects of longshore currents but can slow it

Reversing Current Movement of water back toward ocean Most have same force as wave striking beach Sometimes these currents can be stronger and therefore dangerous Rip current –Strong, narrow flow of water returning to the ocean (through a sand break in a sandbad) after breaking on shore –If trapped in one, DON’T PANIC!! Let current carry you until pull decreases then swim diagonally to shore. –

Rip Current

Opening Assignment 1.Large circular current systems are called _________. These are important because:______________. 2.What causes the deflection of large scale movements over the earth’s surface? What is the direction of the deflection? 3.AT THE SAME LATITUDE, which is colder, the east coast of the USA or the west coast? Explain why.

Answers 1.Large circular current systems are called gyres. These are important because: influence climate. 2.What causes the deflection of large scale movements over the earth’s surface? Coriolis effect caused by the rotation of the Earth. What is the direction of the deflection? To the right in northern hemisphere and to the south in the southern hemisphere 3.AT THE SAME LATITUDE, which is colder, the east coast of the USA or the west coast? Explain why. West coast because the it is on the east side of the pacific gyre

Upwelling Currents can cause surface water to flow away from coast So deep, cold, nutrient-rich water rises to the surface to replace it in a process known as upwelling Upwelling supplies rich amount of dissolved nutrients which feeds plankton –More plankton = more small fish = more big fish –Upwelling is common on west coast of N. & S. America and Africa –Because of abundance of fish, many major fisheries (anchovy & tuna) operate near these areas

Upwelling

XkLuL4https:// XkLuL4

Review of Currents Upwelling Reversing Gyre Longshore Match the correct type of current to the following characteristics: 1.___________: caused by water flowing back to sea after waves break on shore 2.___________:Transports sand and may cause erosion 3.___________: Warm on the west and cold on the east 4.__________: Supplies cold, nutrient rich water to the surface 5.____________: Regulate earths climate 6.____________:Caused by waves breaking on the beach at an angle

Waves

Produced when some form of energy disturbs water Most waves produced by wind but also by earthquakes and gravitational pull of the moon Notes

Water itself is not moving (except in a vertical orbit), energy is passing through it (ex: Human Stadium Wave – the wave appears to move sideways around the stadium when if fact each person only moves up and down)

Wave Characteristics crest - highest point of a wave trough – lowest point of a wave wave height – vertical distance = crest - trough wavelength – distance successive or adjacent crests wave amplitude – distance from still-water level to crest Notes - DRAW picture too

Fetch Fetch: The distance that the wind is blowing over open water The longer the fetch the greater the wave height Notes

Breaking Waves Affected by shape of ocean floor near beaches

Plunging breaker When waves approach steep beach slope they rise up quickly and the wave curls over and topples Destroys wave form Produces crashing sound

Spilling breaker Develops along flatter beaches (Florida) Moves as a line of foam Quiet wave

Wave formation s/development-of-ocean-waves/ s/development-of-ocean-waves/

Other Waves Capillary waves (a.k.a ripples) –smallest waves –stop as soon as wind stops Whitecap –mixture of air and water on a wave –sign of rough weather to come

Other Waves Tsunami – seismic sea wave – caused by undersea earthquake or volcanic eruption –very fast moving (up to 450 mph for up to 2000 miles) –crests can be 100 miles apart –not very noticeable in deep water (only about a 3 foot swell) –can range from ft. high

How waves affect the shore Erosion: the removal of sand from the shore –Rate of erosion depends on: type of shoreline, size and force of waves, number and intensity of storms the shore receives each year Notes

How waves affect the shore Accretion: the placement of “new” sand on the shore –Creates shoreline features such as sandbars and spits (sandbars that are attached to the shore at one side) Notes

How Tsunami’s are formed environment http:// environment news/japan-tsunami-2011-vinhttp://video.nationalgeographic.com/video/ news/japan-tsunami-2011-vin

Review of Waves 1.What causes waves? 2.What two processes affect shore formation? 3.Label the wave below F = D = B to F = D to F = A to B =

Global Impact of Currents g/player/lesson08.htmlhttp://oceanexplorer.noaa.gov/edu/learnin g/player/lesson08.html