字幕表 動画を再生する 英語字幕をプリント Hey Squeaks, did you know that while you were asleep last night, a volcano off the coast of Italy was wide awake? The Stromboli volcano has been awake for at least the last 2,000 years! That means it's been erupting for longer than any other volcano. Stromboli's eruptions happen really often, practically non-stop! At night, its glowing light-shows have reminded some people of a giant lighthouse. [Squeaks squeaks] That's a really good question! How does a volcano like Stromboli form in the first place? Deep inside the Earth -- and I'm talking waaaaay deeper than our fort goes -- it's really hot. It's so hot that the rock that makes up this layer of the earth is actually melted! It's called magma. Now, sometimes magma can collect in a pocket just beneath Earth's surface, and if the magma breaks through all the way to the surface and reaches the air, it's called lava. And now, my friends, you have a volcano on your hands. Lava is bright red and very hot when it first erupts out of the ground. But soon the lava cools down and creates a layer of rock. Over time, many layers build up around the spot where the lava came out, to form the mountain that many of us think of as a volcano. And if the volcano keeps erupting, it keeps growing. With each eruption of a volcano, more magma flows up the tube that forms in the middle, called the vent, and it comes out at the top, called the crater. Then, once more, the lava cools and hardens into solid rock, and the volcano has grown! But not all volcanoes look, or act, the same. Lava can come out of craters in different ways. It depends on the type of volcano. For some volcanoes, like Stromboli, lava shoots out like a fiery fountain. When Stromboli erupts like this, big blocks of lava and stone can be thrown hundreds of meters away. But for other volcanoes, lava just oozes out of the crater, more like a lazy syrup. Over time, this slow-moving lava can create massive volcanoes, too. One volcano like this, called Mauna Loa in Hawaii, is the tallest volcano in the world. And in fact, all of the islands of Hawaii are made of volcanoes that began underwater. They've been growing for millions of years, and over time, all of the layers of lava that have oozed out have built up, until they reached above the surface of the ocean. Our fiery old friend Stromboli, in Italy, formed this way, too. Its whole island is basically one big volcano! So, you don't have to have an underground fort to know that there's a lot of amazing stuff going on beneath the surface of the Earth. There are incredible forces at work all the time shaping the world that we live in. Thanks for watching SciShow Kids! Hey Squeaks! Let's get going before one of our experiments erupts!