1
- 1 year ago
Category
🐳
AnimalsTranscript
00:00Volcanoes. In this video, we're going to learn about different types of volcanoes.
00:12The earth is alive! Not alive like you and me, but the earth is always moving and changing,
00:19and never stays the same. You may see it right before your very eyes, or you may not see or
00:26feel it happen at all. But it's happening right now beneath our feet. The earth is changing.
00:31Let's explore some of the ways the earth changes. Run for your lives! She's gonna blow! It's a volcano!
00:39A volcano is a fracture or opening in the earth's crust through which magma escapes. Deep in the
00:47bowels of the earth beneath the crusts are vast chambers of molten liquid rock we call magma.
00:54Magma can slowly cool and become hardened. Or magma, with trapped gases, can flow and feed
01:01a volcano and rise to the surface of the earth. When magma reaches the surface, it becomes lava.
01:08A volcano may be active, or a volcano may be dormant, which means that it's only sleeping
01:15and may someday erupt. Or a volcano may be extinct, which means that it was once active but will
01:22probably never erupt again. Let's explore three types of volcanoes. Millions of years ago,
01:30the islands of Hawaii emerged from the sea, powered by erupting volcanoes. The formation of the islands of
01:38Hawaii are examples of shield volcanoes. Some of these volcanoes are active and continue to erupt.
01:45Other volcanoes have been dormant for a million years. These volcanoes are massive in area, and have gradual
01:53sloping sides. The eruptions are like fountains, and lava flows are very liquid. The Loihi Volcano,
02:00south of the Big Island of Hawaii, is one actively erupting volcano under the sea. Loihi is a sea mount rising
02:0910,000 feet from the floor of the Pacific Ocean. And as it continues to erupt molten lava, it one day will
02:16become an island all its own in about a hundred thousand years. Shield volcanoes are not as explosive as
02:23cinder cone volcanoes. A cinder cone volcano has straight steep sides. In 1943, Senor Pulido was working in his
02:34cornfield near the village of Paricotin, Mexico. Pulido tells the story that as he and his family were
02:41working in the field, that the earth began to tremble and shake, and right before his very eyes, the ground
02:48swelled to over six feet. A fissure opened, and gray ash and smoke poured into the air, and the sound of a
02:57terrible hiss, and the horrible smell of sulfur. Through the thick smoke, Pulido could not find
03:03his family. He went back to the village and discovered they had arrived there safe and sound.
03:07Through the days and weeks and years that followed, the volcano would continue to grow to over 1300 feet
03:15high, or 396.24 meters. Spewing hot smoke and ash into the air, everyone had to be evacuated and find
03:26another home as thick, slow-moving lava would advance to the villages of Paracotin and San Juan,
03:33which were destroyed. Can you imagine how awful that would be? The Paracotin volcano has been very
03:40important to scientists, as they have seen the birth and rise of a volcano and watch it become dormant.
03:46And though a cinder cone volcano may be terrible, it is no match for the spectacle of a volcano which can
03:54be far more powerful, far more terrible, far more frightening, and more explosive. Of course, we are
04:03talking about the Stratovolcano! A Stratovolcano is characterized by gentle lower slopes, gradually
04:13increasing to steep upper slopes. They are constructed of layers of hardened lava and volcanic ash and pumice.
04:20Stratovolcanoes are known to have violent eruptions, expelling fiery lava fragments through the air like bombs.
04:28Toxic gases fill the air, and massive plumes of ash clouds carry vast distances, making aviation travel
04:36impossible. These volcanoes are dangerous and deadly, and though lava from these volcanoes flows slowly, it
04:43covers and burns and destroys everything in its path. In the Cascade Mountain range of southwest
04:48Washington state, there rises many beautiful snow-covered peaks. Some of them are volcanoes.
04:54One of these volcanic mounts is known as Mount St. Helens. It was no secret that Mount St. Helens had been an
05:02active volcano for hundreds, maybe thousands of years. And volcanologists, scientists who study volcanoes, had been
05:10studying St. Helens, with their equipment watching and waiting for another perhaps major eruption.
05:16It was possible that St. Helens would not erupt in their lifetime. Even with fancy equipment, these things
05:23are difficult to predict. Then came the spring of 1980. For months, tremors and earthquakes shook the ground.
05:30On the north face of Mount St. Helens, a bulge began to form. Volcanologist David A. Johnston was watching and
05:40measuring the growth of the bulge with his lasers. On May 18, 1980, David called out over the radio,
05:47This is it! This is it! The caldera blew with supersonic fury. Everything in the path of this massive eruption was wiped out for eight miles.
05:59David A. Johnston was camped right in the path of the most destructive volcanic eruption in known U.S. history.
06:08250 homes, railways, bridges, highways, all gone. Could Mount St. Helens erupt again? Will you wait and see?
06:18In the world, there are nearly 1,500 potentially active volcanoes. 169 are in the United States.
06:28Is there one near you? Many volcanoes are located along the Pacific Rim, an area that reaches along South and North America,
06:37along the Aleutian Islands of Alaska, down the islands of Japan and the Philippines, Indonesia, New Zealand, and the South Pacific.
06:46This path in the Pacific Ocean is known as the Ring of Fire.
06:51For millions of years, our Earth has been alive with erupting volcanoes.
06:56In addition to those we've explored, and among the most frightening and terribly destructive are
07:03Mount Vesuvius of Pompeii, Krakatoa in Indonesia, and the volcanic complex in Iceland.
07:10And, deep underneath Yellowstone National Park lies enormous chambers of molten magma,
07:18which one day may find its way to the surface and become the most massive supervolcano ever.