The Earth is a watery place. But just how much water exists on, in, and above our planet?
About seventy one percent of the Earth's surface is water-covered, and the oceans hold about ninety seven percent of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you and your dog.
Water is never sitting still. Thanks to the water cycle, our planet's water supply is constantly moving from one place to another and from one form (physical state) to another. Things would get pretty stale without the water cycle!
(Information from: USGS Science for a changing world)
Did you know that you drink dinosaur pee every day? Earth’s water is so old that, statistically speaking, every time you drink a glass of water, you’re probably swallowing a water molecule (H2O) that passed through a dinosaur.
We are all aware that most land plants (e.g. beech trees!) use photosynthesis to grow and produce the oxygen we breathe. But roughly half of the total photosynthesis on Earth occurs in the surface of the ocean, carried out by tiny micro-algae called phytoplankton.
Water is tasteless, almost colourless, transparent and odorless. It also is the only natural substance that is found in all three physical states (liquid, solid and gas) at the temperatures normally found on Earth. Moreover, life totally depends on it. Not bad for a boring looking substance!
Of the small amount that is available as freshwater, only a fraction is readily available for our everyday use (like drinking water). This explains why water is such a precious resource, even though it seems like we have such an abundance of it.
Water also has the power to shape the landscape... but this is next week's story.