Our Round Earth - its Waters (1971)

[Music] it's easy to see that we're looking at the moon the moon's surface is dry there are no oceans here no Lakes no Rivers no streams no water at all the Moon is a dry Place how different it is from the earth the earth is quite wet it has a vast supply of water when we get closer to the Earth we see more water than land most of this water forms oceans you probably know the names of some of them Atlantic is the name of One [Music] Ocean Pacific that's another there's also an Indian Ocean and the Arctic and Antarctic oceans all of these oceans together cover most of the surface of the Earth it's a little easier to see oceans on a globe of the Earth the globe helps us see that the different oceans are connected they're all parts of one large body of water we've seen something of how oceans look from up above what are they like from down below with underwater breathing equipment men have explored some of the shallower parts parts of the oceans these are usually the Parts closest to shore much light and warmth from the Sun reached these shallow areas making it possible for many kinds of plants and animals to live here to explore greater depths men have built vessels somewhat like submarines only Built much stronger the deeper such a vessel Dives the greater the weight of the water above it and the greater the water pressure against it windows in such a vessel must be made very thick Bright Lights help men inside see what's happening around them in deep dark parts of the ocean the long hook in the front is used to collect samples from the ocean bottom samples of water can also be brought inside for study from the surface men use other ways of getting information about ocean depths by lowering equipment on Long cables men can reach down thousands of feet into the water this way they can bring up samples of soil from the ocean floor other sampling devices are used to learn about the water itself all ocean water is not exactly the same same each sample is somewhat different men have taken thousands of samples of ocean water to learn about what it's like at various depths theyve found that ocean water contains many materials including salt ocean water is called salt water salt and other materials found in the ocean come from the land year after year for thousands of years Rivers have been washing these materials into the sea but river water is not saltwater Rivers have only small amounts of salt dissolved in them so we say that rivers are fresh water fresh water is also found in lakes and ponds men direct water into ditches to irrigate their crops plants need water to grow water is needed by animals too all kinds of animals water is also needed by people we've seen that much of this water comes from Rivers ponds and lakes but where does this water come from from a pump yes but where does the pump draw the water from from many feet below below the ground it's called groundwater in some places water flows out of the ground by itself as a spring other places water has been running underground for millions of years wearing away soil and rock many caverns and caves have been formed this way heated water sometimes shoots from the ground forming a geyser where does such water come [Applause] from we know how water gets on the ground from rain and snow some of this water soaks into the ground it's something like what happens to water poured on a sponge it soaks into the sponge deeper and deeper the same sort of thing happens to the ground water soaks into the ground deeper and deeper this is where groundwater comes from what about rain where does rain come from rain comes from clouds clouds are made of water but how how does water get into the air suppose we put a dish of water out in the warm air as the hours go by particles of water slowly rise out of the dish into the air this is evaporation water evaporates the same thing happens to a puddle of water after a rain water evaporates from all over the Earth water evaporates from oceans it evaporates from Lakes it evaporates from rivers and streams water even evaporates from plants plants soak up water from the ground the water in turn passes back into the air through the leaves of each plant from all over the Earth's surface water evaporates Ates into the air at first we don't see this water it's invisible but as it rises it becomes cooler it begins to form tiny droplets these droplets form clouds this is where clouds come from eventually much of this water falls back to the Earth as rain or snow this movement of water is not always as man would like sometimes in some places man gets more water than he needs and there are [Applause] floods other times man gets less water than he needs the land becomes so dry that soil may be blown away it's no wonder that men try to control where water goes a dam can be used to hold back water with a dam it's also possible to direct water to places where it's needed men have learned some useful ways to control water but some of the things men do with water are harmful will there always be enough clean pure water on the earth to provide for the needs of living things what do you [Music] think