Why do scientists think volcanic eruption is a dangerous and beautiful existence?
When it comes to volcanoes, most people immediately think of typical volcanic cones, such as Mount Fuji or Mount Kilimanjaro. It is a symmetrical hill formed by the accumulation of ejected magma. Volcanic cones may form soon. 1943, a farmer in Parikutin, Mexico, was surprised to see smoke coming out of one of his fields. A week later, he dreamily became the owner of a volcanic cone 152 meters high. In less than two years, its height reached 430 meters and its diameter exceeded 800 meters. There are about 10000 such volcanoes on the earth, of which only a few hundred are active volcanoes. However, there is a less famous volcano, which does not build mountains. Such a volcano is so powerful that it suddenly erupts from the ground, leaving a sunken crater (from Latin meaning cauldron). Yellowstone volcano obviously belongs to the second kind, but christiansen can't find the crater anywhere.
At that time, NASA decided to take photos of Yellowstone National Park and test some new high-altitude cameras. A considerate official gave some of the photos to the park authorities, thinking that they could be hung in the visitor center. As soon as christiansen saw these photos, he immediately realized why he had not found the crater: in fact, the whole park-9,000 square kilometers-is a crater. The volcanic eruption left a crater nearly 65 kilometers in diameter-too big to be understood from any angle on the ground. At some point in the past, Yellowstone National Park may be blown to pieces, and its power far exceeds any level known to mankind.
It turns out that Yellowstone National Park is a super volcano. It is located in a huge hot spot-a lava storage place. This storage place is at least 200 kilometers deep on the earth, until it is close to the ground, forming a so-called super hot column. The heat of hot spots provides energy for all the vents, geysers, hot springs and bubbling mud pits in Yellowstone National Park. Below the ground is magma chamber, with a diameter of about 72km-roughly equivalent to the size of a park, and the thickest part is about13km. Imagine a pile of TNT, equivalent to the size of a county in Britain, reaching the sky at 13 km high and reaching the height of the highest cirrus cloud, and you will probably know what tourists in Huangshi National Park are visiting. The pressure of this magma pool on the upper crust pushed up Yellowstone National Park and its surrounding areas, making it about half a kilometer higher than the original height. If there is an explosion, the disaster will be unimaginable. Bill McGuire of University College London said that once it broke out, "you can't get within 1000 km". The result could be worse.
Several super hot columns in Yellowstone National Park, much like martini glasses, are thinner and thinner as they go up, but when they reach the ground, they spread out and become many "big bowls" filled with unstable magma. Some "big bowls" have a diameter of 1900 km. According to the current theory, the super hot column does not always erupt violently, and sometimes it just spews out a lot of lava, just like it happened in the dark rock area of Deccan, India 65 million years ago. The super hot column covers an area of 500,000 square kilometers, and the poisonous gas emitted may have played a role in the extinction of dinosaurs-of course, it is not a good role. Superheated columns may also be the cause of cracks that break the continent.
Such hot spots are not uncommon. At present, there are about 30 active heat pillars on the earth, and many famous islands and islands in the world are related to heat pillars-such as Iceland, Hawaii, Azores, Canary Islands and Galapagos Islands, Pitcairn Island in the central South Pacific and many other islands. But except Yellowstone National Park, everything else is in the ocean. No one knows how or why the hot pillar of Yellowstone National Park appears under the land. Only two things are certain: the crust of Yellowstone National Park is very thin, and the world below is very hot. However, it is a heated debate whether the crust is thinned because of hot spots or because of hot spots. The continental nature of the crust has an important influence on the outbreak of hot spots. Other super volcanoes tend to gurgle, while Yellowstone volcano erupts very violently. This kind of thing doesn't happen very often, but once it happens, you'd better stay away.
It is known that its first eruption was 654.38+65 million years ago. Since then, it has erupted about 100 times, but the last three times have been recorded in writing. The intensity of the last time was equivalent to 1000 times that of Mount St. hellens; The previous time was equivalent to 280 times; God knows how many times the intensity of the previous one was, at least 2,500 times that of Mount St. hellens, but it may be 8,000 times that of the terrible volcano.
We have absolutely nothing to compare with it. The largest eruption in modern times was1August, 883 in Krakato, Indonesia. Its rumble echoed around the world for nine days, shaking the water as far away as the English Channel for half a day. If the material ejected from Krakatoa volcano is compared to a golf ball, then the material ejected from the largest eruption of Yellowstone volcano is like a big ball, and you can hide behind it as a hiding place. According to this ratio, the substance emitted by Mount St. hellens is just a bean.
Two million years ago, Yellowstone Volcano spewed enough volcanic ash to bury new york at a depth of 20 meters or California at a depth of 6 meters. The fossil beds discovered by Mike Walhus in eastern Nebraska were formed by this kind of volcanic ash. That eruption took place in what is now Idaho, but in the past millions of years, the earth's crust was covered at a rate of about 2.5 cm per year, so today it is located below the northwest of Wyoming. The hot spot itself stays where it is, just like an acetylene torch aimed at the ceiling. It left a fertile volcanic plain and became an ideal place to grow potatoes. This was discovered long ago by farmers in Idaho. Geologists like to joke that in 2 million years, Yellowstone National Park will produce French fries for McDonald's fast food restaurants, and people in Billings, Montana will dance around geysers.
The last eruption of Yellowstone Volcano covered all or part of the western 19 state (plus parts of Canada and Mexico)-almost the whole area west of the Mississippi River in the United States. Remember, this is the granary of the United States, which produces almost half of the world's food. Don't forget, volcanic ash won't melt in spring like heavy snow. If you want to plant crops again, you have to find a place to pile up all the volcanic ash. Thousands of workers spent eight months cleaning up 6.5438+800,000 tons of garbage on 6.5 hectares of land in New York World Trade Center. Think about how long it will take to clean up Kansas.
We haven't considered the impact on the climate. The last super volcanic eruption in the world occurred in Doba, northern Sumatra, which has been 74,000 years. No one knows how strong it is, but it must be scary. The ice core in Greenland shows that after the eruption of the Doba volcano, there will be at least six years of "volcanic winter", and God knows how many bad growing periods there will be. It is believed that this outbreak almost destroyed mankind and reduced the global population to less than a few thousand. This means that those thousands of people are the same ancestor of all modern people, which also explains why we lack genetic diversity. In any case, there is evidence that in the next 20 thousand years, the total population of the earth will never exceed several thousand. Needless to say, it will take a long time to recover from the volcanic eruption.
All this is interesting, but it's all hypothetical. Until 1973, something strange happened, and suddenly that assumption became very meaningful: yellowstone lake in the center of Huangshi National Park began to overflow the bank at the end of Hunan and flooded a meadow; At the same time, the water at the other end of the lake mysteriously disappeared. Geologists immediately checked and found that the situation was not good, and the park rose in a large area. This scene of lifting one end of the lake and letting the water flow out from the other end is like lifting one side of the children's play pool. By 1984, the whole central area of the park (over 100 square kilometers) was 1 m higher than that of the park when it was last officially surveyed in 1924. Then at 1985, the central area of the park sank by 20 cm. Now, this area seems to be expanding again.
Geologists believe that there is only one reason-an active magma chamber. There were no super volcanoes in ancient Huangshi, only active volcanoes. It was also around this time that they calculated that Yellowstone volcano erupted on a large scale every 600,000 years on average. The last eruption was 630 thousand years ago. It seems that Yellowstone volcano is going to erupt.
"Maybe you don't feel this way, but you are standing on the largest active volcano in the world." Paul Doss, a geologist in Yellowstone National Park, told me. On a beautiful morning in June, we met at the park headquarters of Mammoth Hot Springs. He just got off a big Harry Davidson motorcycle and shook hands with me. Doss is from Indiana, amiable, soft-spoken and caring. He doesn't look like an employee of the Park Service at all. He has a gray beard and his hair is tied in a braid. Wearing a small sapphire pin on one ear. The uniform of Zhi Park service is a little tight, and it looks like a paunch. He looks more like a blues musician than a government employee. In fact, he is really a blues musician (playing Zhong Qin the Glass). However, he does know and love geology. "This is the best place to study geology in the world," he said, and we got into an old four-wheel drive car and headed for the old faithful fountain. He promised to let me accompany him for one day, no matter what geologist he would be in the park on this day. The first task today is to give a basic lesson to a new group of tour guides.
I don't need to point out that Yellowstone National Park is an extremely beautiful place. There are rich and magnificent mountains, grasslands full of bison, gurgling streams, blue lakes and countless wild animals and plants. "If you are a geologist, this is really the best place to work," Doss said. "There are rocks in Shihokou, Birtu. They have a history of nearly 3 billion years-they can be traced back to three quarters of the earth's birth, and there are mineral springs here." He pointed to several hot springs, hence the name Mammoth Hot Springs. There is everything in the middle, as long as you can think of it. I have never seen a place where the geological conditions are so obvious and beautiful. "
"So you like this place?" I said.
"Oh, not like it, but love this place." His answer was extremely sincere. "I mean, I really love this place." It's cold in winter and the salary is not too high, but when the years are good, it's just ... "
He didn't go on, but pointed to the west. There is a gap in the distant mountain, which just pokes out a highland and catches our eye. He told me that the name of that mountain range is Mount Gala. "The gouges where whole pieces were missing were about 100 km wide. For a long time, no one knew why there was a gap. Later, Bob christiansen thought it must have blown out of the mountains. To blow up a place about 100 km wide in the mountains, you know it will be related to a powerful event. It took christiansen six years to figure it out. "
I asked him why Yellowstone volcano erupted.
I don't know. Nobody knows. Volcanoes are very strange things. We really don't know them. Italy's Mount Vesuvius has been active for more than 300 years. There was an eruption in 1944, and then it stopped. Since then, Vesuvius has been calm. Some volcanologists think it is accumulating energy on a large scale. This is a bit worrying, because there are 2 million people living in Mount Vesuvius and its surrounding areas. However, no one can say for sure. "
"If the Yellowstone volcano is about to erupt, how long will the warning time be?"
He shrugged his shoulders. "We weren't at the scene when it broke out last time, so no one can say for sure what an alarm signal is. It is likely to be a series of earthquakes, some of which will uplift the ground, and the activities of geysers and blowholes may change, but no one really knows. "
"So, it may break out without warning?"
He nodded thoughtfully. The problem, he explained, is that, to some extent, almost everything in Yellowstone National Park that can be used as an alarm signal already exists. "Generally speaking, earthquakes are a precursor to volcanic eruptions, but there have been many earthquakes in the park-last year 1260. Most of them are weak and can't be felt, but they are still earthquakes. "
He said that the change in the activity mode of geysers can also be regarded as a sign, but geysers are changeable and unpredictable. Mousse Spring was once the most famous geyser in the park. It used to spray regularly and grandly, reaching the height of 100 meters, but suddenly stopped spraying at 1888. Then, spraying resumed at 1985, but the height was only 25 meters. Steamboat Spring is the largest geyser in the world, with a height of120m when it is sprayed, but the interval between sprays is as short as 4 days and as long as 50 years. "If it sprays today and sprays next week, it doesn't mean what it will look like next week or next week or 20 years from now," Doss said. "The whole park is changeable, and you can't actually draw a conclusion from any action."
Leaving Yellowstone National Park is not easy. The park attracts about 3 million visitors every year, mainly during the three-month peak period in summer. There are few roads in the park, which are deliberately built very narrow, on the one hand, to slow down the speed of vehicles, on the other hand, to protect natural beauty, and on the other hand, because of the limitation of terrain conditions. In midsummer, you can easily walk through the park in half a day and reach anywhere in the park in a few hours. "People stop when they see animals, no matter where they are," Doss said. "We have bears, bison and wolves here."
In the autumn of 2000, representatives of the US Geological Survey and the National Park Service and several scholars held a meeting and established the so-called Yellowstone Volcano Observatory. There are already four such institutions in China, which are located in Hawaii, California, Alaska and Washington. But strangely, it is not in the largest volcanic area in the world. The Huangshi Volcano Observatory is not so much an institution as a plan-an agreement, in which everyone agrees to coordinate, study and analyze various geological conditions in the park. Doss told me that one of its first tasks is to make an "emergency plan for earthquakes and volcanic eruptions"-that is, an action plan for the crisis.
"There is already one?" I asked.
"No, I'm afraid we don't. But it will be there soon. "
"Isn't it a little late?"
He smiled: "Oh, let's just say it's getting late."
After the plan comes out, it is planned to do this: three people-christiansen of Menlo Park, California, Robert B. Smith of the University of Utah and Doss of the park-will assess the potential catastrophe risk and then make suggestions to the park director. The director will decide whether the park should be evacuated. As for the surroundings, they have no plans. Once out of the park gate, you have to save yourself-if Yellowstone volcano really erupts, this plan won't solve any big problems.
Of course, it may be thousands of years before that day comes. Doss thinks that such a day will never come. "This is because just because there was a model in the past doesn't mean it still applies today," he said. "There are signs that this pattern may be a series of catastrophic outbreaks, followed by a long period of calm. We may be in this quiet period now. At present, there are signs that most of magma chamber is cooling and turning into crystals. It is releasing anger, and you have to hold it in your heart to have a big explosion. "
At the same time, there are many other dangers in Yellowstone National Park and its surrounding areas. This is particularly evident in the night of August 1959. It happened in the Lake Hebergen area, just outside the park. Twenty minutes before midnight that day, a catastrophic earthquake struck Lake Hebergen. The magnitude is 7.5. As far as the earthquake is concerned, it has little impact, but it came suddenly and violently, and the whole hillside collapsed. This happened during the summer tourist season. Fortunately, many people didn't go to Yellowstone National Park as they do now. 80 million tons of rock collapsed from the mountain at the speed of 160 km per hour. Its strength and momentum are so great that its front edge rushes to the height of 120 meters of a mountain opposite the canyon. Part of Rock Creek Camping Park is located in the only place where rocks pass. Twenty-eight campers died, of whom 19 were buried too deep and never found again. Disasters happen quickly and unpredictably. The three brothers shared a tent, but they survived. Their parents slept in another tent next to them, but they were washed away without a trace.
"A big earthquake-I mean a big earthquake-will happen sooner or later," Doss told me. "I can assure you. This is a large fault zone with frequent earthquakes. "
Despite the Hebgen Lake earthquake and other dangers, it was not until the 1970s that Yellowstone National Park was equipped with a permanent seismograph.
If you want to appreciate the power and ruthlessness of geological processes, you must choose a worse example than the Teton Mountains. The Teton Mountains are located in the south of Yellowstone National Park, with rugged and steep cliffs. Nine million years ago, the Teton Mountains did not exist. The land around Jackson Pit was originally a highland plain overgrown with weeds. However, a 64-kilometer-long fault appeared inside the earth. Since then, the Teton Mountains have experienced a major earthquake every 900 years, which is powerful enough to raise it by another 2 meters. Due to this repeated upward vibration for thousands of years, its height has now reached a magnificent 2000 meters.
900 years is an average, and it is also an easily misunderstood number. Robert B. Smith and Lee J. Siegel wrote in "Geological History of the Region-A Window to the Earth's Interior" that the last major earthquake in the Teton Mountains occurred 5000-7000 years ago. In a word, the Teton Mountains may be the most earthquake-prone place on earth.
Hydrothermal eruption is also very dangerous. It can happen at any time and anywhere, and it is completely unpredictable. "You know, according to the road map, we will take tourists into the hot spring pool," Doss told me after we watched the old faithful fountain spray water. "People just come to see this place. Do you know that there are more geysers and hot springs in Yellowstone National Park than the rest of the world combined? "
"I don't know."
He nodded: "There are 10000 places, and no one knows when a new outlet will appear."
We drove to a place called Duck Lake, which is 200 meters wide. "On the surface, the lake is calm," he said. "This is just a big pond. However, there was no such a big pit here before. At some time in the past 15000, there was a big eruption here. Tens of millions of tons of soil, rocks and hot water exploded at supersonic speed. You can imagine what it would be like if this happened under a parking lot of the old faithful fountain or under a tourist center. " He has an unhappy expression on his face.
"Will you call the police?"
"Probably not. The last big eruption of the park took place at 1989, in a place called pork chop geyser. That eruption left a pit about 5 meters wide-it's not very big anyway, but if you just stand in that position, it's already very big. Fortunately, no one was present, so no one was injured, but it happened without any alarm. In the distant past, some eruptions formed a crater with a width of 1.5 km. No one can say when and where this kind of thing will happen again. You can only hope that you weren't standing there when it happened. "
Rockfall is also a kind of danger. 1999, a rockfall occurred in Gadina Canyon. Fortunately, no one was hurt. In the late afternoon, Doss and I stopped at a place and saw a rock protruding from a crowded road. The cracks are clearly visible. "It may fall at any time." Doss said thoughtfully.
"Are you kidding?" I said. Almost every moment, several cars pass by, full of-really-happy campers.
"Oh, no," he continued. "I just said it's possible. It may last for decades. I'm really not sure. People have to admit that you are taking risks here. This is the way it is. "
We walked back to his car and prepared to return to Mammoth Hot Springs. He went on to say, "The problem is that most of the time nothing will happen. The rocks didn't fall, the earthquake didn't happen, and new air holes didn't suddenly appear. Although the underground is very unstable, it is safe in most cases. "
"Just like the earth itself." I said.
"Exactly." He agreed.
Yellowstone National Park is dangerous for tourists and park employees. Five years ago, Doss had this terrible feeling in his first week here. Late one night, three young summer employees did an illegal activity called "soaking in a casserole"-swimming or warming in a hot pool. Although the park didn't disclose this situation for obvious reasons, not all the swimming pools in Yellowstone National Park are boiling hot. Some of you are just comfortable lying in it, and some summer employees have the habit of taking a bath in the middle of the night, although it is against the rules. Those three people are stupid. They don't have flashlights. This is extremely dangerous, because the soil around the hot pool forms a thin hard shell, and people can easily fall into the burning spray holes below. In any case, on their way back to the dormitory, they have to cross a stream that they had to jump over before. They stepped back, arm in arm, counted one, two, three, and then ran and jumped. In fact, it is not a stream at all, but a boiling pool. They can't see clearly in the dark. None of the three people came back alive.
The next morning, on my way out of the park, I thought about it and went to a place called Emerald Pool. Emerald pool is located in the upper geyser pool. Doss didn't have time to take me the day before, but I think I should at least go and see it, because the Emerald Pool is a very historic place.
1965, a team of couple biologists-husband named Thomas Brock and wife named Louis Brock-did an incredible thing in a summer survey. They scooped up a little brown scum by the pool and took it back to study for life. To their great surprise-and finally to more people in the world-it is full of living microorganisms. They discovered the first batch of extreme microorganisms in the world-microorganisms that could live in water that was previously considered too hot, too sour or too sulfur to produce life. Incredibly, all these disadvantages are available in Yaochi, but at least two kinds of microorganisms feel comfortable here. They were later called acidophilic thermosulfur thallus and thermophilic thallus. In the past, people thought that nothing could survive at a temperature above 50 degrees Celsius, but these microorganisms lived comfortably in foul acidic water with a temperature almost doubled.
In almost 20 years, one of the two new microorganisms discovered by Brock and his wife, mesophilia, has been a treasure in the laboratory until a scientist named Cary B. Muhlis in California discovered that thermostable enzymes can be used to exert a chemical magic called polymerase chain reaction. Scientists can use a very small amount of DNA-only one molecule under ideal conditions-to produce a large amount of DNA. This method of gene replication later became the basis of genetic science, which was used in both academic research and forensic work of the police. Mullis won the Nobel Prize in Chemistry from 65438 to 0993.
At the same time, scientists are discovering microorganisms that are more heat-tolerant. Now, they are called thermophilic microorganisms and need temperatures above 80 degrees Celsius. Frances ashcroft wrote in "Life under Extreme Conditions" that the most thermophilic microorganism discovered so far is fumaric acid hot globulin, which lives in the rock wall of ocean blowholes, where the temperature is as high as 1 13 degrees Celsius. The upper limit of life is considered to be about 120 degrees Celsius, although no one actually knows. In any case, the discovery of the Brocks completely changed our view of the biological world. Jay Berg Straahl, a scientist at the National Aeronautics and Space Administration, said: "No matter where we go on the earth-even if we enter the environment that seems most unfavorable to life, as long as there is liquid water and some chemical energy, we can find life."
It turns out that life is much smarter and more adaptable than anyone imagined. We will soon understand that this is a good thing, because the world we live in doesn't seem to completely want us to stay here.