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科技环境

厄立特里亚火山喷发 东非裂谷地质活动频繁

厄立特里亚的纳布罗火山已经喷发了近一周时间。科学家认为,非洲大陆的分裂进程正在加速。

This aerial photo shows a plume of ash rising from the volcano in southern Iceland's Eyjafjallajokull glacier, Monday, April 19, 2010. Scientists say because this volcano is located below a glacial ice cap, magma is being cooled quickly, causing explosions and plumes of grit that can be catastrophic to plane engines, depending on prevailing winds. But scientists in Iceland offered some hope Monday that conditions might be easing, saying the new volcanic ash plume is lower, which would pose less of a threat to commercial aircraft in the future. (AP Photo/Arnar Thorisson, Helicopter.is) ** ICELAND OUT ** ** zu unserem KORR. *

东非的纳布罗火山喷发让科学家大吃一惊。此前,该火山并没有显现出即将喷发的征兆。纳布罗火山沉寂许久,上一次喷发估计还是15 000年前的事。此外,对"非洲之角"的地质研究工作目前还很欠缺。

冰岛等国都已建成了密集的观测站,但在厄立特里亚等东非国家却缺少这类科研基础设施。德国波茨坦地质研究中心的火山学家瓦尔特(Thomas Walter)认为,如果能够取得当地的第一手观测数据,就有可能预测出火山的喷发时间。不过他也指出,以目前的技术手段,尚不能准确预测火山喷发的持续时间及规模。

Nabro, a stratovolcano in the northeast African nation of Eritrea, rumbled to life late in the evening on June 12, 2011, following a series of earthquakes. The Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite captured this natural-color image the next day. Initial reports from news agencies and the Volcanic Ash Advisory Center in Toulouse, France, proclaimed the eruption to be occurring at Dubbi, a volcano further south. But later reports from volcanologists, field scientists, and the satellite image above appear to confirm the eruption at Nabro. There are no historical reports of eruptions at Nabro before today. The volcano is part of a larger complex with several nested calderas nearby. It is part of the East African Rift, where the African continent is slowly pulling apart due to tectonic plate movements.

纳布罗火山喷发卫星照片

纳布罗火山位于东非裂谷带,该地区是世界上地壳活动最活跃的地区。地质学家预测,几百万年后,非洲大陆将会由于火山运动从该裂谷带分裂。而阿拉伯半岛则是已经分裂出去的一个板块,红海及亚丁湾便是东非大裂谷北侧的延伸。在东非裂谷带上有非洲最高山、著名的乞力马扎罗山,还有世界上第二大的淡水湖--维多利亚湖。

据地质学家介绍,东非裂谷带的分裂运动已经持续了约2亿年。目前,裂谷两侧的大陆板块漂离速度介于每年0.7~2.6厘米之间。在地质学上,这是相当快的速度。

而人类能够直接感受到的,则是伴随着这个进程的火山喷发及地震。该地区每年都会发生2~5起火山喷发,地震也相当频繁。火山学家瓦尔特认为,该地区的地震发生频率还是相对稳定的。

作者:Helga Hansen 编译:文山

责编:雨涵