Much of the rain that falls on the land started as water vapour which evaporated from the surface of the seas and oceans into the atmosphere. as the air moves around the globe, the water can be transported over great distances and under the right conditions, the water vapour forms clouds and rain. Rain that falls on the land can run over, or though the ground into streams and rivers, eventually returning to the sea. this is called the water cycle, and it is also the main reason why the sea is salty.Read more

You will often read that the saltiest sea on earth is the Dead Sea, but this is really an inland lake, not a true sea. The scientific term for saltiness is, “salinity” and the world oceans have an average salinity of about 35 ‰, but this does vary across the planet. For example, the Mediterranean Sea, the Red Sea and the Arabian Sea all have relatively high salinity, while the Black Sea and Baltic Sea both have relatively low salinity.Read more

Most sand is made from very small particles of rocks that have been broken down by the weathering action of rain, ice and wind, or by the action of waves beating against our shores. The colour of sand usually reflects the type of rock or specific minerals within them.Read more

If you look at the Earth from space, what you see is that the sea is in fact, the largest and most important feature of our planet. The sea covers almost 71% of the Earth’s surface, approximately 361 million square kilometres (139 million square miles). The Sea contains 97% of all the water on the planet and by volume it is the single largest habitat for life on Earth. Although most coastal seas are rather shallow (less than 200 m deep), because of the great size of the deep ocean basins, the average depth of the sea is around 3800 m.Read more