Rocks: Where They Come From

[Music] did you ever go exploring to look for rocks Don and his father did one day they took a drive in the country and then stopped to look at something can you see what it is it's a huge hole in the ground Don has never seen anything like this before Solid Rock going deep deep down into the Earth his father tells him it is a quarry he also says that the Earth we live on is made up mostly of Rock The Rock that's taken from this Quarry is called Granite Granite is one kind of rock that is used for building things Granite is a hard rock rock as Don finds out when he tries to scratch it with a coin hard rocks do not scratch easily Don is going to save the piece of granite it will remind him of his visit to the Quarry later that day Dawn and his father drive to another place here they walk down toward the river near the river they see many inter ing rocks rocks of many different sizes and shapes Don notices that some of the Rocks here are made up of layers father explains that this is sandstone a kind of rock made up of layers of sand this Sandstone was formed long ago underwater millions of years ago a huge sea covered this place Rivers flowed into this sea the moving water carried sand and mud that sank to the bottom something like this the sand settled through the water to form a layer as more sand falls a second layer is formed the weight of the sand and water over millions of years helped to press the sand together to form Sandstone Don is rubbing off some of the grains of sand rocks that have been formed underwater like Sandstone are usually quite soft a hard rock like DA's piece of granite can easily wear away a softer Rock like Sandstone Don is going to save a piece of sandstone now you'll have an example of a soft rock too father says he can show Don some other kinds of rocks this museum has a collection of rocks and Don will learn more about them in the museum there's a room that's something like a classroom the sign here says learn by doing anyone can come here and try the simple experiments that da and his father will do also in the room Don sees a collection of different kinds of rocks here's an aquarium filled with different layers of sand but what's Don's father doing he's using his hand to show how water pressed down on the layers of sand to form sandstone here's another way to show what happens when grains of sand are pressed together Don thinks the round hard things on the table look like pieces of sandstone father thinks he can make one like them you take the mold and fill it with the mixture of sand and clay the mold with the moist sand is then placed in a vice when the vice is tightened it squeezes the sand together with a great deal of force they'll leave the mold in the vice for a while and Don knows that's to let the sand dry Dawn hopes that their experiment will turn out like this this piece and the others that were made in the vice look much like dun's piece of sandstone of course he knows it takes millions of years for real Sandstone to form and it takes millions of years for granite to form too Granite belongs to a group of rocks which are made by fire and a great deal of heat that's why Granite is so hard to explain how some rocks are made by fire and heat father points to a picture of a volcano Don knows where he saw this volcano he remembers seeing this same volcano in a film through a volcano like this hot liquid sometimes comes up from deep down in the earth onto the land after the liquid comes out of the volcano and is cooled it becomes hard it forms a kind of rock called lava here's a sample of lava like lava Granite was also a hot liquid deep in the earth when it cooled it became a very hard rock is there another kind of hot liquid that gets hard when it cools Don remembers one it was just the other day when father was making paper weights out of lead it took a great deal of heat to melt the lead when the hot lead was poured into the mold it quickly cooled it became hard in much the same way as lava and granite become hard so dawn has learned that some rocks are made by fire and a great deal of heat and others such as Sandstone are made by water Dawn now has a piece of sandstone which is very interesting it's a fossil because it has an outline or imprint of a plant in it any Rock we find that has an imprint of animals or plants is called a fossil Don will be able to see more fossils in another room in the museum here's a fossil fish Don can clearly see the head and the tail fossils are found not only in Sandstone but also in another kind of rock made in water Limestone when limestone is buried under other layers of rock it may be pressed and squeezed until after millions of years it can be changed or made over into Marvel another kind of rock marble is a beautiful hard rock that we often see in buildings pieces of marble can be carved into statues too Don wonders can other rocks be changed over yes if Sandstone is pressed and squeezed for millions of years it too can be changed or made over into a rock called quartzite Shale is another kind of waterm made rock it can be changed into slate slate may be cut into pieces and used to make roofs well Don is learning much about rocks but can he remember some of the important things this exhibit will help him rocks made by water are s Stone Limestone and Shale among the rocks made by fire and heat are granite and lava among the rocks changed or made over are slate and marble now they're going to check their sense Stone experiment the sand in the mold is quite dry now it's quite hard too Don thinks it's very much like a piece of sandstone he'll take it home with him Don has discovered many interesting things about rocks you can too perhaps you might like to start a collection of rocks and learn where they come [Music] from