Ocean Waves and Tides

Ocean Waves and Tides

Waves • A Wave is a rhythmicmovement that carries energy through matter or space. • In oceans, waves move through seawater

Waves Caused by: • Wind • Earthquakes • Gravitational force of the Moon and Sun.

Parts of a Wave • Crest – highest point of a wave • Trough – lowest point of a wave • Wave Height – vertical distance between the crest and the trough • Wavelength – horizontal distance between two crests or two troughs

Wavelength Crest Wave Height Still Water Trough Wave Parts

Wave Formations • Form when energy is transferred from a source to the ocean water • Most common from WIND

Wave Movement • When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward. • Water does NOT travel with waves

Wave Movement • When a wave breaks against the shore, the crest outruns the trough and the crest collapses. • Called a breaker. • In this case, water does move forward and backward.

Wave energy • Wind keeps adding more energy to waves • WIND SPEED: • -Wave period is time between 2 wave crests or 2 wave troughs • -Speed of wave= wave length/wave period

Waves reaching Shore • Most waves reach shore and transfer energy to beach

Why Waves Break • The ocean floor slows the bottom of the wave, yet the top is moving at original speed • Breaker is when wave’s crest crash on shore

Waves Caused by Wind • When wind blows across a body of water, friction causes the water to move along with the wind. • Wave Height depends on – • Wind speed • Distance over which the wind blows • Length of time the wind blows

Tides • The rise and fall in sea level is called a tide. • Caused by a giant wave. • One low-tide/high-tide cycle takes about 12 hrs and 25 min. • Tidal range is the difference in ocean level between high-tide and low-tide

What is the Tidal Range? • HT = 30 ft, LT = 20 ft • HT = 20 ft, LT = 12 ft • HT = 50 ft, LT = 20 ft

Tidal Range • The tidal range is the difference between the level of the ocean at high tide and low tide.

Why Tides Happen • Moon’s gravity pulls on every particle of Earth • Moon’s pull decrease with increase in distance • Areas closer to the moon have stronger pull • Liquids are pulled more easily by gravity

Where Tides Happen • Area of ocean that directly faces moon is pulled most • Area furthest from moon has little effect from moon’s pull • Ocean water bulges toward moon

Gravitational Effect of the Moon • Two big bulges of water form on the Earth: • one directly under the moon • another on the exact opposite side • As the Earth spins, the bulges follow the moon.

High tides and Low tides • High tide- bulges that form as a result of moon—Ocean level is higher than normal • Low tide- water is pulled toward opposite area where high tide is occurring • Each day usually has 2 high tides and 2 low tides

Timing of Tide • Moon revolves around earth slower than earth rotates • Takes 24 hours 50 min to rotate to face the moon again • High tides and low tides happen 50 minutes later each day

Tidal Variations • Sun has gravitational pull but far, when sun and moon pull together- greater tide • Spring Tides • Earth, Moon, and Sun are lined up • High Tides are higher and Low Tides are lower than normal • During new moon and full moon

Spring TIDES

Neap Tides • Earth, Moon, and Sun form right angles • High Tides are lower and Low Tides are higher than normal • During different phases of moon

NEAP Tides • Neap tides are especially weak tides. • Moon & Sun are perpendicular to each other. • Moon & the Sun’s gravity cancel each other out.

Mont St. Michel • A great example of tidal surge is the castle Mont St. Michel in France. • The tides surrounding the “Mount” can vary by 14 meters between high and low tides, and move in as rapidly as 1 meter a second. • The “Mount” is connected to the mainland by a thin natural land bridge, which before modernization was covered by the sea at high tide, and revealed during the low tide.

The End

Ocean Waves and Tides