Sunday, November 25, 2012

"The Tornado" from VOA

This article was orignally published in
April, 2012



BARBARA KLEIN: This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.

BOB DOUGHTY: And I'm Bob Doughty. This week, we explore the science of tornadoes. These violent storms strike in many parts of the world but happen most commonly in the United States.

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BARBARA KLEIN: Tornado season has begun in the United States.

Last Tuesday a series of storms tore across the Dallas-Fort Worth area in Texas. The tornadoes damaged or destroyed hundreds of homes. Yet no deaths were reported.

On March second, more than forty tornadoes moved through the Ohio and Tennessee Valleys, and the South. Reports say the storms killed at least thirty-nine people in five states.

A tornado is a violently turning tube of air suspended from a thick cloud. It extends from a thunderstorm in the sky down to the ground. The shape is like a funnel: wide at the top, narrower at the bottom.

A funnel cloud touches down in Orchard, Iowa, on June 10, 2008
Tornadoes form when winds blowing in different directions meet in the clouds and begin to turn in circles. Warm air rising from below causes the wind tube to reach toward the ground. Because of their circular movement, these windstorms are also known as twisters.

The most severe tornadoes can reach wind speeds of three hundred twenty kilometers an hour or more. In some cases, the resulting paths of damage can stretch more than a kilometer wide and eighty kilometers long.

BOB DOUGHTY: With a tornado, bigger does not necessarily mean stronger. Large tornadoes can be weak. And some of the smallest tornadoes can be the most damaging. But no matter what the size, tornado winds are the strongest on Earth. Tornadoes have been known to carry trees, cars or homes from one place to another. They can also destroy anything in their path.

Tornadoes have been observed on every continent except Antarctica. But experts say they are most commonly seen in the United States. On average, more than one thousand are reported nationwide each year.

The National Oceanic and Atmospheric Administration keeps records of tornado sightings. It says tornadoes kill seventy people and injure one thousand five hundred others nationwide in an average year.

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BARBARA KLEIN: Tornadoes are observed most often in the middle of the United States, where the land is mostly flat. The area where the most violent tornadoes usually happen is known as “Tornado Alley.” This area is considered to extend from north central Texas to North Dakota.

Tornadoes can happen any time of the year. But most happen from late winter to the middle of summer. In some areas, there is a second high season in autumn.

BOB DOUGHTY: Tornado seasons are the result of wind and weather patterns. During spring, warm air moves north and mixes with cold air remaining from winter. In autumn, the opposite happens. Cold weather moves south and combines with the last of the warm air from summer.

Twister, March 2012
Tornadoes can strike with little or no warning. Most injuries happen when flying objects hit people. Experts say the best place to be is in an underground shelter, or a small, windowless room in the lowest part of a building.

People driving during a tornado are told to find low ground and lay flat, face down, with their hands covering their head. People in the path of a tornado often just have minutes to make life-or-death decisions.

BARBARA KLEIN: The deadliest American tornado on record was the Tri-State Tornado of March eighteenth, nineteen twenty-five. It tore across Missouri, Illinois and Indiana. About seven hundred people were killed.

Between March and May of last year, there were one thousand one hundred fifty-nine confirmed tornadoes across the United States. Scientists say that is the most on record for any three-month period. The most active month was last April, when seven hundred fifty-eight tornadoes were confirmed. That is the most ever for any month.

Last April, the country also broke a thirty-seven year old record for the largest tornado outbreak. A "tornado outbreak" is often defined as six or more tornadoes produced by the same weather system within a day.

Scientists say the one hundred ninety-nine tornadoes on April twenty-seventh were the most for any single day. They say the storms killed three hundred sixteen people – the most ever in modern records for a twenty-four hour period.

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BOB DOUGHTY: No two tornadoes look exactly the same. And no two tornadoes act the same way.

Even a weak tornado requires the right combination of wind, temperature, pressure and humidity. Weather experts can identify these conditions. And, when they observe them, they can advise people that tornadoes might develop. But they are not able to tell exactly where or when a tornado will hit. Tornado warnings still depend in large part on human observations.

Usually a community will receive a warning at least a few minutes before a tornado strikes. But each year there are some surprises where tornadoes develop when they are least expected.

BARBARA KLEIN: The tornado reporting system involves watches and warnings. A tornado watch means tornadoes are possible in the area. A tornado warning means that a tornado has been seen. People are told to take shelter immediately.

Yet tornadoes can be difficult to see. Sometimes only the objects they are carrying through the air can be seen. Some night-time tornadoes have been observed because of lightning strikes nearby. But tornadoes at night are usually impossible to see.

Tornadoes that form over water are called waterspouts. But tornadoes cover a much smaller area than hurricanes, which form over oceans.

Tornadoes can be measured using wind speed information from Doppler radar systems. Tornadoes usually travel in a northeasterly direction with a speed of thirty-two to sixty-four kilometers an hour. But they have been reported to move in other directions and as fast as one hundred seventeen kilometers an hour.

BOB DOUGHTY: In the United States, the force of a tornado is judged by the damage to structures. Scientists inspect the damage before they estimate the severity of a tornado. They measure tornadoes on the Enhanced Fujita scale or the EF scale.

Ted Fujita studying the
physics of the tornado
Ted Fujita was a weather expert who developed a system to rate tornados in the nineteen seventies. The EF scale is a set, or collection, of wind estimates. They are based on levels of damage to twenty-eight different kinds of structures and other objects. Tornadoes that cause only light damage are called an EF-zero. Those with the highest winds that destroy well-built homes and throw vehicles great distances are called an EF-five.

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BARBARA KLEIN: Some people make a sport out of watching and following tornadoes. They are called tornado chasers or storm chasers. Their work can be seen in the extreme weather videos that are increasingly popular on television and on the Internet.

Some chasers do it just because it is their idea of fun. Others do it to help document storms and warn the public. Still others are part of weather research teams.

Two years ago, an international team of scientists completed a tornado research project called VORTEX2. More than one hundred researchers traveled throughout America’s Great Plains in two thousand nine and two thousand ten. They used weather measurement instruments to collect scientific information about the life of a tornado. The goal of the project was to examine in detail how tornadoes are formed and the kinds of damage they cause.

Last year, a film about the VORTEX2 project was released. The film includes never before seen images of tornadoes. To safely capture up-close film footage of tornadoes, some project participants traveled in a seven-ton, armored tornado intercept vehicle directly into tornadoes as they formed.

BOB DOUGHTY: The National Weather Service says the United States gets more severe weather than any other country. For one thing, it is also bigger than most other countries. And it has many different conditions that create many different kinds of weather.

There are seacoasts and deserts, flat lands and mountains. The West Coast is along the Pacific Ocean, which is relatively calm. The East Coast is along the Atlantic Ocean, which is known for its hurricanes. These strike mainly the southeastern states.

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BARBARA KLEIN: This SCIENCE IN THE NEWS was written by Brianna Blake and George Grow. June Simms was our producer. I'm Barbara Klein.

BOB DOUGHTY: And I'm Bob Doughty. Read and listen to our programs at voaspecialenglish.com. Join us again next week for more news about science, in Special English, on the Voice of America.

Sunday, November 4, 2012

"The Valley of 10,000 Smokes" from Edcon Publishing





A place you will read about: Mount Katmai a mountain in Alaska.

Something you will read about: algae a group of plants, which usually live in water, that do not have true roots, stems, or leaves.

Following its eruption, Mt. Katmai has become a national monument visited by thousands of tourists. In June 1912, explosions boomed across Alaska. Centering near Mt. Katmai on the upper Alaskan Peninsula, they frightened Eskimos from nearby villages, and not a moment too soon. A new volcano had formed on Mt. Katmai's slope and began to erupt. Tons of ash and rock poured out, spreading an enormous dark cloud across the sky and a blanket of ash over the summer landscape. A cloud of smoke overtook the steamer Dora, at sea 55 miles away, and ashes sifted down on the boat. Soon, those aboard could not see their hands before their faces. Through the gloom, lightning flickered and thunder crashed. A fierce wind began to blow and the temperature rose.

Children in Kodiak, 1912. They're
making volcanic ash pies.
People on land fared little better. At Kodiak, 100 miles southeast of Mt. Katmai, the sky was inky dark at noon. Ash fell so abundantly that its weight made roofs collapse all over town. People coughed and choked as they groped their way about; birds died trying to fly through the black ash-filled air. It was all over in three days.

But what happened in the region around Mt. Katmai? No one knew the Eskimos had fled for their lives and did not wish to return.
Not until three years after the event did someone finally undertake to investigate the result of the 1912 eruption. In July of 1915, Dr. Robert Griggs set out with a party of explorers to visit Mt. Katmai. He and his crew made the trip by boat. As they approached Katmai Bay due south of the mountain, they could see that the water was still filled with the floating wreckage of trees and bushes. Over the land, the sky was still dark, filled with ash. The darkness made the barren landscape even more desolate.

Robert Griggs' photo of Katmai
Valley, 1915
Before the eruption, Katmai Valley had been green in the summertime, a place where trees grew tall and wildlife could be found in abundance. Now it was a place of death, where neither plant nor animal life had been able to survive. Griggs and his party tramped through the valley across a layer of sticky mud past skeleton forests of dead trees. A great wind blew up, stinging the weary travelers with the glass-sharp pieces of volcanic rock. They were forced to drink water thick with bits of rock; they forded patches of treacherous quicksand, sinking to their knees, never able to touch solid bottom. They struggled up hills where, for each step they took, they slid back a little through the fine volcanic sand.

Even solid ground could not be trusted, for ash had fallen on snowfields and then been packed down. Afterward, the snow had melted out from beneath the crust of ash, leaving hollows beneath the valley floor. The explorers knew the ground could collapse beneath their feet at any moment.

As the mountain peaks loomed ahead, Griggs' party came across a fantastic, geological feature - a colossal chasm. It was nearly as deep as the Grand Canyon - 4,000 feet from rim to floor.
The explorers camped and waited for the clouds over Mt. Katmai to move off, for Griggs was determined to see what had happened to Katmai's three-pointed peak. When the sky began to clear, Griggs was astonished to see not a peak but a flattened stub. Mt. Katmai had caved in on itself, becoming shorter by some 800 feet!

Griggs returned again in 1916 for another look. During this expedition, he and his party climbed Mt. Katmai. The mountain was covered by clouds and not until the party had reached the top did the cloud cover thin out. At Mt. Katmai's summit the explorers stopped short, for they were perched on the edge of a huge chasm. In its depths they saw a lake of milky blue cradling a small horseshoe-shaped island. The mountain had a huge hole at its core where solid rock had once been. Now the hole was filling with water from melting snowbanks on its steep sides. The chasm was 4,460 feet deep and three miles long.

The party went around the lake to look down at the valley on the landward side of Mt. Katmai, where a fantastic scene met their gaze. The valley floor was covered with thousands of cracks and vents, and from each a column of steam arose. Some were no more than threads of white, but others roared hundreds of feet into the air. Griggs later wrote, "The whole valley, as far as the eye could reach. was full of hundreds, no thousands ... of smokes, curling up ... Sleep that night was impossible ... I had seen enough to know that we had accidentally discovered one of the great wonders of the world." And so Griggs decided to name the place the "Valley of Ten Thousand Smokes."

The Valley of 10,000 Smokes
This steaming valley so fascinated Griggs that he returned in 1917 to descend to the valley floor. The explorers were cautious as they reached their destination, for they knew that the ground was treacherous, underlain with cracks and hollows. They feared the boiling-hot steam and poisonous fumes that rose from the vents all around them. Nevertheless, they camped among the valley's "smokes" and even learned to use the rising steam in place of campfires for their cooking. They discovered that a stick thrust into some columns of steam would burn. The very ground they walked on was so warm that they were forced to sleep on top of their bedding. Yet around the steam vents they found a trace of life. Tiny, simple plants called algae could survive the heat and even thrive in this fantastic place.

Today, the area surrounding Mt. Katmai, including the Valley of Ten Thousand Smokes and the cluster of volcanic mountains nearby, has become a national monument. Katmai National Monument covers more than 4,000 square miles, the largest wilderness area in the park system. Much has changed since the Griggs expeditions.

G-23 In the Valley of Ten Thousand Smokes, the "smokes" have all but disappeared, but it is a desolate place still. Layers of yellowish ash have been eroded to form weird, fluted slopes, as if giant's fingers had clawed through an enormous pile of clay. Life is beginning to return to the valley. Mosses, bushes and young trees have sprung up here and there, and visitors to the monument may spot bears, moose and wolves.

The Valley today, at sunset.
Over the years, Mt. Katmai has changed, too. In 1922 a geologist who had been with Griggs on his 1919 expedition returned to Mt. Katmai. He found the chasm empty, the lake gone. All he could see was a muddy bottom with a few pools of water and a vent through which a column of mud spurted into the air. But the lake soon filled again. Since then, the lake water has bubbled and steamed, giving early warning of brief eruptions in nearby volcanoes. The lake water has been rising, and the horseshoe-shaped island has disappeared. Year by year, the lake is growing deeper.

If you ever have the opportunity, visit Katmai. You'll find it a fantastic place, where skeleton forests shelter struggling young trees, where the rivers run thick with volcanic ash and the snow slides past steaming vents into a lake at the heart of a mountain. And then, of course, there's always the chance that, as one explorer put it, "Some other mountain will blow up." Perhaps you'll be lucky enough to see it when it does!

COMPREHENSION CHECK

1. The explosion on the Alaskan Peninsula was caused by
a. enormous black cloud.
b. thunder.
c. an erupting volcano.
d. a deep chasm.

2. Falling ash made roofs collapse
a. at Dora, 100 miles to the southeast.
b. at Kodiak, 100 miles to the southeast.
c. at an Eskimo village in Anchorage.
d. a mile away from Mt. Katmai.

3. In July of 1915, Dr. Robert Griggs
a. coughed and choked as he groped his
way about.
b. tried to fly through the ash-filled air.
c. set out to explore Mt. Katmai.
d. fled for his life with the Eskimos.

4. Three years after the eruption, Katmai Valley
a. became more beautiful.
b. remained unchanged.
c. received little sunlight.
d. was settled by Eskimos.

5. The chasm discovered in 1915
a. was nearly as deep as the Grand Canyon.
b. was twice as large as the Grand Canyon.
c. was barely noticeable.
d. was filled with boiling lava.

6. Dr. Griggs found that the three-pointed peak had changed
a. on his first visit.
b. on his second visit.
c. after he had discovered the columns of steam.
d. after he descended to the valley floor.

7. The story of the Mt. Katmai explosion would probably be found in a book about
a. great monuments of the Eastern
United States.
b. great wonders of the world.
c. great explorers from 1850 to 1900.
d. population changes in Alaska.

8. Dr. Griggs traveled to Mt. Katmai
a. four times.
b. once.
c. twice.
d. three times.

9. Another name for this selection could be
a. "Alaska's Explosions."
b. "Kodiak National Monument."
c. "The Life of Robert Griggs."
d. "Katmai National Monument."

10. This selection is mainly about
a. the Eskimos.
b. how a volcano erupts.
c. camping near Mt. Katmai.
d. a fantastic place in Alaska.