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00:00Hi kids, today we will learn about a natural disaster that is a volcano.
00:11So let's get started.
00:14Before learning about volcanoes, we need to learn what are layers of the earth, what are
00:21fault lines, and what are tectonic plates.
00:27So let's first learn about the layers of the earth.
00:32The earth is made up of three layers.
00:37The outer crust is a layer on which we live.
00:42It is estimated to be about 1,800 miles deep.
00:49Then there is the mantle, and then the core, or the inner and outer core.
00:57The mantle, that is the outer core, is made up of molten material and gases.
01:06Molten materials are solids, like rock, that have turned into liquids because of extreme
01:14heat.
01:16The name of molten rock, and other gases in the earth's mantle, is magma.
01:25Magma is liquid made up of many crystals, fragments, and gases.
01:33When they cool off on the earth's surface, they turn into magmatic, or igneous, rocks.
01:42Now let's learn what are fault lines.
01:46Fault is a planar fracture in earth's crust.
01:51They result from action of tectonic plates.
01:57Tectonic plates are pieces of the earth's crust, and the uppermost mantle, together
02:05referred to as the lithosphere.
02:10Now we know what are the layers of earth, fault line, and also what are tectonic plates.
02:20So now we are ready to learn what is a volcano.
02:27A volcano is an opening, or vent, in the earth's topmost layer, called crust.
02:35Through this opening, extremely hot mixture of gases, lava, ash, and other burning substances
02:45called lava, comes out.
02:51Volcanic eruptions create elevations that look like big mountains.
02:58Volcanoes occur at weak zones, or points in the earth's crust.
03:05Now let's learn various parts of volcanoes.
03:10Magma, molten rock material, which is beneath the earth's surface, is called magma.
03:21Lava, molten rock material, when it comes out of the earth's surface, it's called lava.
03:31And on solidification, this lava turns into igneous rocks.
03:40Vent, an opening in the earth's surface through which volcanic materials escape, is called
03:48vent.
03:50A vent is not visible in a volcano.
03:56The visible opening is called crater.
04:01It is the mouth of the volcano.
04:06This crater surrounds the volcanic vent.
04:11Ash, fragments of lava or rock smaller than 2 millimeters in size, that are blasted into
04:21the air by volcanic explosions, is called as ash.
04:28Ash cloud, a cloud of ash formed by volcanic explosions.
04:36Now let's see how and why volcanoes erupt.
04:42Sometimes extreme pressure builds up across the fault lines, and a sudden eruption occurs,
04:52and molten matter and ash comes out of the opening in the earth, which is called vent.
05:03When the molten matter is still inside the earth, we call it magma.
05:10And when it comes out of the earth's surface, we call it lava.
05:17Lava can be as hot as 2,200 degrees Fahrenheit.
05:23It is red hot when it comes out of the vent, and turns gray or black when it cools down.
05:33Some volcanoes are very, very violent, and some are not as violent.
05:41There are different types of volcanoes all over the earth's surface.
05:48Volcanoes exist even beneath the ocean.
05:53On the ocean beds, common gases that comes out of the volcanoes are water vapor, carbon
06:03dioxide, sulfur dioxide, hydrogen chloride, and hydrogen fluoride, and hydrogen sulfide.
06:14Now let's learn about some recent volcanic activities.
06:20Some active volcanoes exist in Iceland, Hawaii, Indonesia, Ecuador, and Mexico.
06:34Volcanoes in Philippines and Papua New Guinea have recently calmed down.
06:43There are about 500 active volcanoes on the earth.
06:50The most active and biggest volcano on the earth is Mauna Loa volcano.
06:58Though we call volcano a natural disaster, but unlike floods, wildfires, earthquakes,
07:08and avalanches, volcanoes are not as bad as they seem.
07:16They have some positive effects to them, too.
07:21Let's see some positive effects of volcanoes.
07:26Volcanoes create scenic beauty and also attract tourists, so it becomes a tourist destination.
07:35Areas near volcanoes become very good sources of geothermal energy that can be tapped to
07:43produce electricity and many more purposes.
07:50The surrounding areas of volcanoes also become rich in nutrients, and the soil becomes much
07:58more fertile.
08:01Now let's learn some negative effects of volcanoes.
08:09The area where volcanoes erupt becomes devastated, that is, it destroys life and property.
08:20Ash that comes out of volcanoes has very bad effect on the ozone layer.
08:28The previous landscape and natural beauty of the place is destroyed.
08:36So kids, today we learned a lot about volcanoes.
08:41Now you may go ahead and take a quiz to learn more.
08:45Bye-bye!