The Earth often called the ‘blue planet’. Seen from space, it looks blue because of all the water on its surface. Three quarters of the globe are covered with seas and oceans, representing 361 million square kilometers of salt water! The world’s seas and oceans contain practically all the water on the planet, the rest is mostly fresh water stored in the form of ice in polar ice caps* and glaciers and river water.
The marine environment is vast complex and hard to access. We don’t know much about it and studying this milieu* is both costly and complicated. And yet the world’s oceans play a vital role in the planetary environment; we must learn more about them in order to protect it.
The world’s oceans and adjacent seas and all the organic and inorganic natural resources they contain are indispensable to the survival of our planet as we know it today. Safeguarding* the air we breath, the water we drink, the food we eat and the climate we live in depends on the oceans.’ This was the declaration made by UNESCO’S intergovernmental oceanographic commission (IOC) at the world summit for Sustainable Development held in Johannesburg in September 2002.
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Their beginnings:
How were the oceans created? In order to answer this, we must go back four and a half billion years to the earliest ages of the earth. There were many active volcanoes at the time, spewing out thousands of tons of magma. This gooey, burning hot liquid rock contained enormous quantities of gas that created the earth’s first atmosphere known as the primitive atmosphere, and which was full of steam. With the cooling of the earth, the water vapor condensed and became. Dilution rains fell to the ground and accumulated in the low-lying areas of the land, creating ponds and lakes and, little by little, the world’s first seas and oceans. Over time the composition of these bodies of water changed, but not their quantity, which has always remained the same since the very beginning and represents one and a half billion cubic kilometers of water!
Sea Fish Video
Salty water:
In the beginning the sea water was fresh water. During hundreds of million years since sea water came into being it has been continually loaded with mineral salts and biological matter. These substances are carried by rivers and result from the decomposition of rocks beneath the sea and from gases that escape from the Earth’s crust when volcanoes erupt.
Ocean floors:
Ocean floors are not flat but have highly contrasted reliefs. Because the oceanic crust is cut up into pieces, ocean floors are mountainous and their shapes change. In places the crust fissures and forms what is called the mid oceanic ridges. Ranging from 1 to 4 kilometers height and almost as wide, these enormous marine mountain chains stretch 60,000 kilometers over the globe like the seams of a baseball. Magma rich in minerals from the depths of the Earth spills out on to the ocean floor at these ridges, continually creating new oceanic crust. In some locations the magma spews out violently in the form of an undersea volcanic eruption. In other spots, the ocean floor disappears when a portion of oceanic crust slides into one of the deep sea trenches, whose depth varies from 6,000 to 11,000 meters.
Just imagine for a second that the oceans have been drained. We would be able to see a landscape of mountain chains, plains, volcanoes and very deep valleys.
