HOW DOES A VOLCANO ERUPTATE? - Jamy's Essentials | Lumni скачать в хорошем качестве

HOW DOES A VOLCANO ERUPTATE? - Jamy's Essentials | Lumni

This volcano is Mount Agung, in Bali, Indonesia. You've probably heard of it... It emerged from its slumber in November 2017. The last major eruption took place in 1963. It was devastating. 1,500 people lost their lives. Ash fell more than 1,000 km away, as far as Jakarta. When a volcano emerges from its slumber, it's impossible to know when the eruption will occur or how intense it will be. That's why in November 2017, in Bali, as soon as the volcano started smoking, the authorities declared maximum alert and ordered the evacuation of 100,000 people around the volcano. So there are two main categories of volcanoes: red and gray. Red volcanoes are also said to be effusive. They mainly eject fluid lava, which forms long flows that stretch along the slopes. Agung is one of the gray volcanoes. These are explosive volcanoes. They eject enormous masses of gas and incandescent ash, which, upon falling, can sometimes form avalanches that tumble down the slopes of the volcano at several hundred km/h. They are extremely dangerous. Why do volcanoes explode? Beneath the surface lies what is called the magma chamber, the magma reservoir. This is molten rock from the Earth's mantle. Incidentally, we speak of magma when this molten rock is in the magma chamber; and of lava when it flows outside. The magma chamber communicates with the outside world through what is called a chimney. When the magma is very viscous, it eventually clogs the chimney. This is what happened with Agung. Meanwhile, activity continues in the magma chamber. Gas bubbles form. They expand and rise toward the surface, pushing the magma out. Since the vent is blocked, the magma cannot escape. The pressure increases, until it becomes strong enough to burst the cap. The volcano's summit is then pulverized. A huge amount of dust, debris, incandescent rock, and gas is projected into the sky, forming a huge cloud that eventually falls back down and cascades down the slopes, destroying everything in its path. These are called pyroclastic flows. Temperatures can reach 500°C. Today, there are more than 1,500 active volcanoes on the planet's surface. Gray volcanoes generally form in so-called subduction zones, where tectonic plates overlap, such as in Indonesia. They are often more dangerous than red volcanoes because their eruptions are sudden and their lava flows very rapid. Conversely, the slow flow of lava from red volcanoes gives populations time to seek shelter. Today, fortunately, most volcanoes are under close surveillance. Scientists are able to predict most major eruptions and provide timely warnings to populations at risk. ####################################### Even more content at: https://education.francetv.fr/ Join us on: Facebook:   / francetveducation   Twitter:   / francetveducation   Instagram:   / francetveduc   Snapchat:   / francetveduc