[by:¿É¿ÉÓ¢Óï¡«www.utensil-race.com]
[00:00.00] Good morning.
[00:02.02] Let's get started!
[00:04.03] Today we are going to move on to the next chapter volcano.
[00:08.16] The first thing we need to know about volcanoes is that they are like a double edged sword: volcanoes both destroy and create.
[00:16.47] The catastrophic eruption of Mount St. Helens in 1980 made clear the destructive power of a volcano.
[00:23.45] However, over a long period of time, even longer than human memory and record, volcanoes have played a key role in forming and modifying the earth.
[00:34.26] More than 80 percent of our planet's surface is of volcanic origin.
[00:38.54] Gas emissions from volcanoes formed the earth's earliest oceans and atmosphere.
[00:44.41] That supplied the essential ingredients to evolve and sustain life.
[00:48.31] Ironically, the volcanic soils have attracted people to live on the flanks of volcanoes.
[00:54.37] So, as more people live in the regions or near the regions of active volcanoes, we should be more aware of the hazards of volcanoes.
[01:02.38] Probably, you have heard of the story of Mount Vesuvius.
[01:06.20] The story is set in the year 79 when Vesuvius suddenly exploded and destroyed Pompeii, a Roman city.
[01:14.48] Within a few hours, hot ash and dust buried the city so thoroughly that its ruins were not uncovered for nearly 1,700 years.
[01:23.52] The eruption of Mount St. Helens mentioned just now had a huge impact on all the continental states as well as Hawaii and Alaska.
[01:33.53] So. volcanoes are not that far away from us.
[01:37.25] The world volcano comes from a little island called" Vulcano" in the Mediterranean Sea off Sicily.
[01:44.45] In ancient times, people believed that Vulcano was the chimney of Vulcan, who is the blacksmith of Roman gods.
[01:52.05] He made iron stuff for Jupiter and Mars and made Vulcan as the outlet of his hot lava fragments and clouds of dust.
[02:00.35] Today know that volcano eruptions are not super natural but can studied and interpreted by scientists.
[02:07.29] Probably you wonder what volcanoes are.
[02:09.56] Volcanoes are very different from other mountains in that they are not formed by folding and crumpling but by uplift and erosion.
[02:17.28] A volcano is most likely to be a mountain built around a vent that connects reservoirs of molten rock below the surface of the Earth.
[02:26.03] The term volcano also refers to the opening or vent through which the molten rock and relevant gases are expelled.
[02:33.42] During an episode of activity, a volcano commonly displays a distinctive pattern of behavior.
[02:40.10] Some mild eruptions merely discharge steam and other gases, whereas other eruptions quietly let out a lot of lava.
[02:49.33] The most spectacular eruptions consist of violent explosions with great clouds of gas debris into the atmosphere.
[02:57.38] There are about 500 active volcanoes in the world, and those volcanoes have erupted at least once within the recorded history.
[03:05.43] 50 of those 500 are in the United States Hawaii, Alaska, Washington, Oregon and California.
[03:14.34] Most of American volcanoes are hidden under the seas.
[03:18.21] Many volcanoes are in and around the Mediterranean Sea.
[03:22.31] Near the island of Vulcano, the volcano Stromboli has been in a state of continuous, mild eruption since early Roman times.
[03:31.40] At night, sailors in the Mediterranean can see the glow from the fiery molten material that is thrown into the air.
[03:38.49] Therefore, Stromboli has been called" the lighthouse of the Mediterranean."