Ocean composition
salinity A measure of the amount of salts in water.
WAVES, CURRENTS AND TIDES OCEAN MOTION WAVES, CURRENTS AND TIDES
Currents What are currents? Causes - “Rivers” of circulating water - Wind - Rotating Earth - Density Changes
Surface current – ocean current powered by the wind blowing across the surface of the water, moves only the upper few hundred meters of seawater, horizontally.
Surface Ocean Currents Broad, slow drifts; never cross equator Wind generated; circular gyres Ocean current powered by the wind blowing across the surface of the water, moves only the upper few hundred meters of seawater, horizontally.
Upwelling – upward circulation of water in the ocean that brings deep, cold water to the top.
Density current Circulation pattern in the ocean that forms when a mass of more dense seawater sinks beneath less dense seawater. (cold or salty water is more dense)
Importance Of Deep Currents Upwelling Brings deep water to surf. Circulates nutrients up Moves plankton & larvae
Coriolis effect - N. Hemis – clockwise; Right The Earth’s rotation causes moving air and water to turn left in the south and right in the northern hemisphere. - S. Hemis – counterclockwise; Left
Gyre - A circular motion or vortex of water in the ocean Gyre - A circular motion or vortex of water in the ocean. (traps plastic trash in the middle)
Wave – rhythmic movement that carries energy through matter or space
Waves look like hills and valleys; the crest is the highest point and the trough is the lowest point.
As a wave passes, energy moves forward; the water molecules remain in about the same place.
Wave height is the vertical distance between crest and trough.
Wavelength is the horizontal distance between crests or troughs of two adjacent waves.
A breaker is a collapsing wave.
The rise and fall in sea level, called a tide, is caused by a giant wave produced by the gravitational pull of the Sun and the Moon
Tides The rhythmic rise and fall of the ocean’s water High tide = rising, incoming tide, flow Low tide = receding, outgoing tide, ebb Slack tide = vertical movement stops
Tides are very long, slow waves They have a wave period of 12 hours 25 min Tidal day is 24 hours 50 min NJ has 2 high and 2 low tides daily
What Causes Tides? 1. Gravitational pull of sun & moon on Earth Moon closer, therefore > effect Like magnet, pulls water away from surface = TIDAL BULGE
2. Centrifugal Forces Bulge on opposite side because centr. force > pull of moon Produced by motions of Earth, sun, & moon
Tsunami Waves
TSUNAMI “TIDAL WAVE” Caused by undersea quake or volcano Wavelength = ~150 mi. Wave height = 6” – 1’ Can NOT perceive in boat Speed > 500 mph Slows down to ~25 mph at shore; water builds up to ~65+ ft
Creation of a Tsunami
Distance bet. Moon & Earth Perigee Tides Moon closest to earth, very high tides (causes flooding) Apogee Tides Moon farthest away from earth, very low tides
Types of Tides Spring Tide - Moon and sun are in direct line with one another Results in Tidal Range = vertical distance between high & low tides 2x’s/month
Neap Tide sun and moon are at right angles Pulls cancel each other out – causes a weak pull unusually low tidal range 2 x’s / month
High tide Low tide
Tidal Range The difference in height between successive high and low tides.
Low tide – later, as the trough of the wave approaches, sea level appears to drop.
Ch. 19 The Ocean Floor
Basin A low area on Earth in which an ocean formed when the area filled with water from rain and moisture from volcanic eruptions.
Continental shelf – gradually sloping end of a continent that extends beneath the ocean.
Continental slope- feature of the ocean basin that dips steeply down from the shelf to the bottom.
Abyssal plain Flat seafloor area4000-6000 below the surface of the water, formed by the deposition of sediments
Mid-ocean ridge Area where new ocean floor is formed when lava erupts through cracks in the ocean floor.
Trench- Long, narrow steep-sided depression in the sea floor formed where one crustal plate is sliding underneath another one.