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Yellowstone's Volcanic Plume Even Bigger Than Thought

(2011-04-17 00:46:03)
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分类: 时文阅读翻译(雅思 考研)

Yellowstone's Volcanic Plume Even Bigger Than Thought

                              黄石公园火山喷发柱甚至比想像中的要大

Yellowstone's <wbr>Volcanic <wbr>Plume <wbr>Even <wbr>Bigger <wbr>Than <wbr>Thought



Electric method gives new view of supervolcano's plumbing, study says.

研究发现,电法给了超级火山柱新的观点。

 

Richard A. Lovett

for National Geographic News

Published April 13, 2011

国家地理新闻 Richard A. Lovett  2011年4月13号发表

The giant plume of hot rock feeding the Yellowstone supervolcano may be even bigger than thought, scientists have discovered.

The volcanic plume had previously been imaged using seismic tomography. This method uses the speeds of seismic waves from distant earthquakes to map features of the crust and upper mantle in 3-D—similar to the way medical CT scans use x-rays to map the human body.

科学家发现的黄石超级火山填充地下贮热岩巨大火山柱可能甚至比想像中的大。

此火山柱早已成像用于地震层析成像。这个方法使用来自远地地震的地震波的速度以绘制地壳和上地幔的3-D图像---和医学CT扫描仪用X射线绘制人体的方法相似。

Earlier, seismic studies had shown that the magma chamber that fuels Yellowstone's geysers lies atop of a plume of unusually hot, and therefore soft, rock shaped like a tilted tornado. (Related: "Yellowstone Has Bulged as Magma Pocket Swells.")

Based on seismic data, the plume appears to slant downward at a 60-degree angle, extending about 150 miles (241 kilometers) west-northwest, toward the Montana-Idaho border. (See "Under Yellowstone, Magma Pocket 20 Percent Larger Than Thought.")

早期,地震研究已发现岩浆房为黄石公园的喷泉的填满燃料,此喷泉在非正常的热的火山柱的顶部,而且因此柔软,岩变形像倾斜的龙卷风。(相关:“黄石公园已膨胀的岩浆储源膨涨”)

根据地震数据,火山柱出现呈60度向下倾斜,向西部或西北部延展了大概150英里(241公里,接近了蒙大拿州和爱达荷州的交界处。(看“在黄石公园下面,岩浆储源比想像中的大20%)

The latest research is instead based on the plume's electrical conductivity. This data also shows a tilting plume, but the new study suggests the plume dips at a shallower, 40-degree angle and extends at least 400 miles (643 kilometers) westward.

Each technique also shows a different depth for the plume, although that discrepancy is due to the methods' differing capabilities. Electrical conductivity can "see" just 200 miles (322 kilometers) deep. But seismic readings can see as deep as 410 miles (660 kilometers)—and the previous data showed the plume extending that far.

最新的研究反而是建立在火山柱的电导率。这个数据也发现这个倾斜的火山柱,但是新的研究认为火山柱倾斜了40度角度,并且向西方延伸了至少400英里(643公里)。

每种技术也展示火山柱的不同的深度,尽管相差是因为方法上不同的能力。电导率可以“看到”200英里(322公里)深。但是地震扫描器可能看到410英里深(660公里)---并且早前数据认为火山柱延伸到这么远。

"It's like in medical imaging, you can use ultrasound or you can use MRI," said study leader Michael Zhdanov, a geophysicist at the University of Utah in Salt Lake City. Both methods show different aspects of the same structures.

“这就是像医学成像,你可以使用超音波或者你可以使用MRI(核磁共振成像magnetic resonance imaging),”研究负责人MZ说到,他是盐湖城犹他州大学的地理学家。两种方法展示相同结构的不同的一面。

Yellowstone Plume Sheathed in Hot Water

For the new study—accepted for publication in an upcoming issue of the journal Geophysical Research Letters—Zhdanov examined Yellowstone's plumbing with magnetotelluric imaging.

黄石公园火山柱覆盖了热水湖

这些新的研究---被接受发表在地理研究信件期刊中即将来临的问题---Zhdanov用大地电磁成像检查黄石公园的火山柱。

This technique uses dozens of monitoring stations to measure the intensity of ultralow-frequency electromagnetic waves generated in the ionosphere, an electrically charged layer of Earth's upper atmosphere.

These waves penetrate deep into Earth, all the way to the upper mantle, where they are affected by variations in the electrical conductivity of the materials they encounter.

这种技术使用了很多监视站以测量在电离层产生的超低频率电磁波的密度,地球上层大气带电荷层。

这种电磁波探索地球深处,所有的方法都只到达上地幔。他们在地幔处碰见材料的电磁率的不同影响了他们。

Magnetotelluric imaging allowed Zhdanov's team to map not only the hot rock of the plume but also a shadowy zone surrounding it made of partially molten rock and areas impregnated with hot, salty water. (See Yellowstone pictures.)

In addition to showing a larger plume, the new data reveal some intriguing details, said Kenneth Pierce, a geologist at the U.S. Geological Survey's Bozeman, Montana, office who was not part of the study team.

大地电磁成像技术不仅可以让Z的团队绘制出火山柱的地下贮热岩,而且可以绘制火山柱阴影区域,这些阴影地方是由熔融岩石和充满热盐水充满区域组成的。(看看黄石公园图片。)

除了展示更大的火山柱,新的数据发现一些有趣的数据,KP说到,他是蒙大拿州的美国地质勘测的博兹曼机构的地理学家,他并不是这个研究小组的成员。

For example, the new images show the plume's eastward extent corresponding to the location of a previously inferred "hot spot swell" of elevated terrain east of Yellowstone National Park, Pierce said.

This region marks where heat rising from the leading edge of the plume is pushing rock up, as tectonic forces cause the plume to drift eastward.

例如,Pierce说到,新的图像揭露火山柱的东方延伸区域与早前推断出黄石公园东方上升地带的热喷泉的位置一至。

这个区域标志来自火山柱主要边缘的热度正在把岩石往上拱,如构造作用力导致火山柱向东方漂移。

Larger Plume Doesn't Signal Impending Eruption

The fact that both techniques show an overall similar shape to Yellowstone's plume is comforting, said Peter Cervelli, deputy scientist in charge of the Yellowstone Volcano Observatory, who was also not part of the study team.

更大的火山柱并不是火山即将喷发的火山信号

事实上两种技术都展示黄石公园火山柱正处于缓和状态,有一种完全的相似性,PC说到。他是黄石公园火山观测台代表科学家,他也是不是这个研究小组的成员。

"It's always reassuring when an entirely different methodology gives you a similar answer," Cervelli said. "It gives you reassurance that you're converging on the truth."

But he warns that it may be too early to properly interpret some of the details in the data, such as the hot spot swell.

“当一种完全不同的技术给了我们相似的答案还是让人安心的。”C说到,“它让你安心,你是一直活在真相中。”

但是他警告,真实的翻译这些数据里的一些数可能为时尚早,比如热喷泉的数据。

"It is exciting [that] we are seeing details we haven't seen before," he said. "But I wouldn't make too much of [them] until they're corroborated by an independent data stream." (Take a Yellowstone quiz.)

Study leader Zhdanov cautions against misconstruing a larger plume as proof that the Yellowstone supervolcano is on the verge of erupting. (See "When Yellowstone Explodes" in National Geographic magazine.)

“我们正看着以前没有的数据是一些很刺激的事迹,”他说到。“但是我不能得到过多的数据直到他们被独立的数据流证实。”(做一个黄石公园的简单测试)

研究负责人Z警告反对误解把当火山柱当成了黄石国家公园的超级火山在喷发边缘的证据。(看看国家地球杂志的“当黄石公园爆发”)

The new findings instead bring scientists a step closer to understanding the magmatic plumbing that underlies Yellowstone and similar regions around the world, he said. Ultimately this data might help scientists determine which currently dormant volcanic regions are primed to erupt hundreds to thousands of years in the future.

(See "Sleeping' Volcanoes Can Wake Up Faster Than Thought.")

In addition, Zhdanov said, the data "can help us build better geological models of the crust and upper mantle for mineral exploration and general understanding of geological structure."

这项新的发现反而把科学家带上了一个更接近在黄石公园和世界范围内相似区域下的岩浆喷发的新的阶段,他说到。最后这个数据可能帮助科学家知道哪些当前的死火山将在未来的几十万年后喷发。

(看看“死火山比想像中醒得更早)

引外,Z说到,这种数据“可以帮匀我们修建更好的地壳和上地幔地理模型,以用于矿物开采和地理结构的普通了解。"

http://news.nationalgeographic.com/

                                                                                                                                     4.16译

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