Ocean Sand,Waves and Tides

11:39 SANDY BEACHES Rocky and sandy shores share many of the same characteristics: - wave shock - changing temperatures - changing salinity - desiccation - predation - good food supply Life “on the floor at the shore” is the most difficult marine environment due to lack of stability.

Sand is constantly in motion and so zonation is less distinct than on rocky shores. Beach zonation is determined by daily tides. 1. Supratidal - upper beach area where materials are stranded by high tide (strand line). Because sand contains little food, scavengers must search along the strand line for beach wrack (decaying organisms). Inhabitants adapt by burrowing to reduce abrasion and escape the heat and predators. ex: sea oats, fleas, ghost crabs, insects, birds, reptiles, and rats

No two beaches have the exact same sand No two beaches have the exact same sand. From the red sand of Prince Edward Island to the sugary, white sand of Siesta Key, Florida to the jewel-like pebbles on some Hawaiian beaches, sands have an amazing variety of color and texture.

2. Intertidal - area from high to low tide; least stable area with the highest diversity of life. The sand is wet by the capillary action of evaporating water. ex: cord grass, bacteria, phytoplankton, worms 3. Subtidal - always just under water; most stable surface ex: eel grass, crab, shrimp, sand dollars, flounders, mollusks

In the winter, high energy waves erode the beaches pulling sand back into the sea. Summer waves are weaker and deposit sand on the beach (foreshore) where dunes can form. Dunes occur throughout the world but are largest on coasts with a wide continental shelf to supply the sand to build dunes.

Succession of dune communities follows this pattern: 1. Pioneer: Winds blow sand off the beach where it is trapped by sea grasses. Their roots stabilize the sand and dunes begin to form. NOAA Sea grasses are protected by law.

The windward dune face usually has a gradual slope, while the leeward side is steep - (called a berm). It prevents land breezes from blowing sand back into the ocean. 2. Juvenile: Behind the dune, is the swale - a low area where breezes are deflected and the result is furnace-like temperatures.

3. Mature: Secondary dunes form behind the swale 3. Mature: Secondary dunes form behind the swale. They are vegetated with woody shrubs and eventually a maritime forest develops. Beaches are protected by the dune. Dunes are held in place by grasses. Grasses come from seeds deposited by birds feeding and nesting on the shores. Birds build beaches and dunes!

Types of sand…. Volcanic Ash Coral Sand Glass Sand Immature Sand Gypsum Sand Ooid Sand Silica Sand Black Sand Green Sand Desert Sand Garnet Sand AND MANY MORE….

MAGNIFIED SAND!!!!

Waves A Wave is a rhythmic movement 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 Movement When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward.

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.

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

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.

Gravitational Effect of the Sun Spring Tides Earth, Moon, and Sun are lined up High Tides are higher and Low Tides are lower than normal

Gravitational Effect of the Sun Neap Tides Earth, Moon, and Sun form right angles High Tides are lower and Low Tides are higher than normal

Types of waves (not caused by wind): 1. Seiche waves are without a crest or trough. They cause the rocking motion in bays and marinas as the thermocline shifts. 2. Rogue waves are caused when wave trains traveling at different speeds and directions meet. They appear suddenly and may capsize boats. 3. Tidal waves are a combination of storms and high spring tides. They are very different from a tsunami.

4. Tsunamis are the result of earthquakes on the ocean floor 4. Tsunamis are the result of earthquakes on the ocean floor. They are very long, low invisible waves in the open ocean. They are very different from a tidal wave. By the time they reach the shore and break, the wave height may be 100 ft. high and may travel at 400 miles/hour. In 1883, Krakatau was completely destroyed by a tsunami and volcano that killed 36,000 people. Krakatau

The hour that shook Japan…