OCEAN
An ocean (from Ancient Greek (Okeanos); the World Ocean of classic antiquity) is a body of saline water that composes a large part of a planets hydrosphere. In the context of Earth, it refers to one or all of the major divisions of the planet's World Ocean – they are, in descending order of area, the Pacific,Atlantic,Indian, Southern (Antarctic), and Artic Oceans.
Oceans cover about 70% of the Earth's surface. The oceans contain roughly 97% of the Earth's water supply.
The oceans of Earth are unique in our Solar system. No other planet in our Solar System has liquid water (although recent finds on Mars indicate that Mars may have had some liquid water in the recent past). Life on Earth originated in the seas, and the oceans continue to be home to an incredibly diverse web of life.
Why are the Oceans Salty?
As water flows in rivers, it picks up small amounts of mineral salts from the rocks and soil of the river beds. This very-slightly salty water flows into the oceans and seas. The water in the oceans only leaves by evaporating (and the freezing of polar ice), but the salt remains dissolved in the ocean - it does not evaporate. So the remaining water gets saltier and saltier as time passes.
Why is the Ocean Blue?
Sunlight is made up of all the colours of the rainbow: red, orange, yellow, green, blue, and violet. Some of the sunlight is reflected off the surface of the water, reflecting the colour of the sky. Some of the sunlight penetrates the water and is scattered by ripples and particles in the water (this tinges the appearance of the ocean with the colour of the particles). In deep water, much of the sunlight is scattered by the oxygen in the water, and this scatters more of the blue light. Water absorbs more of the red light in sunlight; the water also enhances the scattering of blue light.
What Causes Waves?
The winds cause waves on the surface of the ocean . The wind transfers some of its energy to the water, through friction between the air molecules and the water molecules. Stronger winds (like storm surges) cause larger waves.
Waves of water do not move horizontally, they only move up and down (a wave does not represent a flow of water).
If this type of storm forms in the western Pacific Ocean, it is called a typhoon. Hurricanes often travel from the ocean to the coast and on to land, where the wind, rain, and huge waves can cause extensive destruction. Generally, when a hurricane moves over land (or over cold ocean waters) the storm begins to weaken and quickly dies down because the storm is fuelled by warm water. On average, there are about 100 tropical cyclones worldwide each year; 12 of these form in the Atlantic Ocean, 15 form in the eastern Pacific Ocean and the rest are in other areas. Hurricane season is the time when most Atlantic Ocean hurricanes occur; it is from June 1 until November 30. In the eastern Pacific Ocean, hurricane season is from May 15 until November 30.
The weather symbol for a hurricane is:
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Tsunami :
Tsunamis (sometimes called tidal waves) are different from surface waves; they are usually caused by underwater earthquakes, volcanic eruptions, or landslides.
Hurricane :
A hurricane is a powerful, rotating storm that forms over warm oceans near the Equator. Another name for a hurricane is a tropical cyclone. Hurricanes have strong, rotating winds (at least 74 miles per hour or 119 kilometres per hour), a huge amount of rain, low air pressure, thunder and lightning. The cyclonic winds of a hurricane rotate in a counter clockwise direction around a central, calm eye.
If this type of storm forms in the western Pacific Ocean, it is called a typhoon. Hurricanes often travel from the ocean to the coast and on to land, where the wind, rain, and huge waves can cause extensive destruction. Generally, when a hurricane moves over land (or over cold ocean waters) the storm begins to weaken and quickly dies down because the storm is fuelled by warm water. On average, there are about 100 tropical cyclones worldwide each year; 12 of these form in the Atlantic Ocean, 15 form in the eastern Pacific Ocean and the rest are in other areas. Hurricane season is the time when most Atlantic Ocean hurricanes occur; it is from June 1 until November 30. In the eastern Pacific Ocean, hurricane season is from May 15 until November 30. The weather symbol for a hurricane is:
. Tsunami :
A tsunami (pronounced sue-nahm-ee) is a series of huge waves that can cause great devastation and loss of life when they strike a coast.
Tsunamis are caused by an underwater earthquake, a volcanic eruption, an sub-marine rockslide, or, more rarely, by an asteroid or meteoroid crashing into in the water from space. Most tsunamis are caused by underwater earthquakes, but not all underwater earthquakes cause tsunamis - an earthquake has to be over about magnitude 6.75 on the Richter scale for it to cause a tsunami. About 90 percent of all tsunamis occur in the Pacific Ocean.
