How does the Earth's crust grow at divergent plate boundaries? A unique opportunity in Afar, Ethiopia.

地壳如何在不同的板块边界处生长？

• 批准号: NE/E005284/1
• 负责人: Timothy Wright
• 金额: $ 86.93万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FE005284%2F1
• 关键词: How; does; Earth; crust; grow

The African continent is slowly splitting apart along the East African rift valley, a 3000 km-long series of deep basins and flanking mountain ranges. This process may eventually lead to the formation of a new ocean, but on a time scale of millions of years. In the remote Afar depression in northern Ethiopia, Earth's outermost shell, a relatively rigid, ~150 km-thick tectonic plate, has been stretched and heated to the point of rupture. Upwelling rocks from Earth's mantle partially melt, rise, and then cool to form a new oceanic plate. so much that a new ocean has nearly been formed. Here, we have the unprecedented opportunity to witness the process of plate rupture and upwelling of molten rock (magma). Normally, this process occurs within shallow seas, or along the established seafloor spreading centres deep under the sea; in Afar, though, we can actually walk across the region as it happens. Satellite observations of the earth show that tectonic plates move apart, on average, very slowly: usually at a few centimentres per year, or about the rate of fingernail growth. Very occasionally, however, sudden large movements occur, often with devastating consequences. In September 2005, a series of fissures opened along a 60 km section of the Afar depression, as the plate responded catastrophically to forces pulling it apart. Over about a week, the rift pulled apart by 8 metres, and dropped down by up to 1 metre. As told by local people, a series of earthquakes signalled the rise of a block of molten rock to the surface on September 26, and ash darkened the air locally for 3 days. At the same time, satellites tracking the region showed that the surface above nearby volcanoes subsided by as much as 3 metres, as magma was injected along the fissure below the surface. The rapidity and immense length of rupture are not unexpected, but have never before been measured directly. The Afar depression is so hot and dry that there is almost no vegetation to obscure the volcanic and sedimentary rocks exposed on its top surface; this also means that we can use satellites image the them and to measure the way that the Earth's surface changes as faults move, and as pressurised molten rock buoyantly rises and moves up and along the length of fissures within the rift valley. In the nine months since the first major earthquakes, more dramatic surface changes have continued to take place, and earthquakes continue to stir the earth, and local inhabitants. We are proposing a major set of experiments that will bring together experts on Earth deformation, Earth's magnetic and electrical fields, and on magma movement and eruption to this unique natural laboratory. Over the next five years, this team of UK, Ethiopian, US, and New Zealand scientists will collaborate to answers to fundamental questions of plate tectonics: . How do the different layers of the plate stretch apart? . Where does molten rock form and rise to form new oceanic crust? . How does the molten rock move up to the surface? Satellites will image the earth from above, and sensors will record sound waves from distant and near earthquakes and natural magnetic signals to image the thickness of the rock layers the plate comprises. We will also collect and analyse the composition of rocks from young volcanoes in the same region. The Earth history deduced from compositional variations in space and time will give us clues as to when and how often similar sorts of events happened in the past / and may happen again in the future.

非洲大陆正沿着东非裂谷慢慢分裂，东非裂谷是一系列3000公里长的深盆地和两侧山脉。这一过程最终可能导致新海洋的形成，但时间尺度为数百万年。在埃塞俄比亚北方偏远的阿法尔洼地，地球的最外层，一个相对坚硬的，约150公里厚的构造板块，已经被拉伸和加热到破裂的地步。从地幔中涌上来的岩石部分融化，上升，然后冷却，形成一个新的海洋板块。以至于一个新的海洋几乎已经形成。在这里，我们有前所未有的机会见证板块破裂和熔融岩石（岩浆）上涌的过程。通常情况下，这一过程发生在浅海，或者沿着海底深处已建立的海底扩张中心;然而，在阿法尔，我们实际上可以在这一过程中步行穿过该地区。卫星对地球的观测表明，板块的移动速度平均来说非常缓慢：通常每年只有几厘米，或者说大约是指甲生长的速度。然而，偶尔会发生突然的大规模运动，往往会造成毁灭性的后果。2005年9月，阿法尔凹陷的一个60公里长的部分出现了一系列沿着的裂缝，因为该板块对将其拉开的力量做出了灾难性的反应。在大约一周的时间里，裂缝被拉开了8米，并下降了1米。据当地人说，9月26日，一系列地震标志着一块熔岩上升到地面，火山灰使当地空气变暗了3天。与此同时，跟踪该地区的卫星显示，由于岩浆沿着地表以下的裂缝注入，附近火山上方的地表下沉了多达3米。破裂的速度之快和长度之长并不出人意料，但以前从未直接测量过。阿法尔洼地又热又干，几乎没有植被来掩盖暴露在其顶部表面的火山岩和沉积岩;这也意味着我们可以使用卫星对它们进行成像，并测量地球表面随着断层移动而变化的方式，以及随着加压熔融岩石的上升和移动，以及沿着裂谷内裂缝的长度。自第一次大地震以来的九个月里，更戏剧性的地表变化继续发生，地震继续搅动地球和当地居民。我们提出了一系列重要的实验，将把地球变形、地球磁场和电场以及岩浆运动和喷发方面的专家聚集到这个独特的天然实验室。在接下来的五年里，这个由英国、埃塞俄比亚、美国和新西兰科学家组成的团队将合作回答板块构造的基本问题：板块的不同层是如何伸展开的？.熔岩在哪里形成并上升形成新的洋壳？.熔岩是如何上升到地表的？卫星将从上方对地球进行成像，传感器将记录远距离和近距离地震的声波以及自然磁信号，以成像该板块所包含的岩层厚度。我们还将收集和分析同一地区年轻火山的岩石成分。从空间和时间的成分变化中推断出的地球历史将为我们提供线索，以了解过去发生类似事件的时间和频率，以及未来可能再次发生。

项目成果

Magmatic history of Dabbahu, a composite volcano in the Afar Rift, Ethiopia

• DOI: 10.1130/b30560.1
• 发表时间: 2013
• 期刊: Geological Society of America Bulletin
• 影响因子: 4.9
• 作者: L. Field;J. Blundy;A. Calvert;G. Yirgu

Upper mantle anisotropy of southeast Arabia passive margin [Gulf of Aden northern conjugate margin], Oman

• DOI: 10.1007/s12517-011-0477-2
• 发表时间: 2012-09-01
• 期刊: ARABIAN JOURNAL OF GEOSCIENCES
• 作者: Al-Lazki, Ali;Ebinger, Cindy;Al-Toobi, Khalfan
• 通讯作者: Al-Toobi, Khalfan

First recorded eruption of Nabro volcano, Eritrea, 2011.

首次记录了纳布罗火山的爆发，厄立特里亚，2011年。

• DOI: 10.1007/s00445-015-0966-3
• 发表时间: 2015
• 期刊: Bulletin of volcanology
• 影响因子: 3.5
• 作者: Goitom B;Oppenheimer C;Hammond JO;Grandin R;Barnie T;Donovan A;Ogubazghi G;Yohannes E;Kibrom G;Kendall JM;Carn SA;Fee D;Sealing C;Keir D;Ayele A;Blundy J;Hamlyn J;Wright T;Berhe S
• 通讯作者: Berhe S

Magma storage conditions beneath Dabbahu Volcano (Ethiopia) constrained by petrology, seismicity and satellite geodesy

• DOI: 10.1007/s00445-012-0580-6
• 发表时间: 2012-07-01
• 期刊: BULLETIN OF VOLCANOLOGY
• 影响因子: 3.5
• 作者: Field, L.;Blundy, J.;Yirgu, G.
• 通讯作者: Yirgu, G.

Thermal models of dyke intrusion during development of continent-ocean transition

• DOI: 10.1016/j.epsl.2013.09.018
• 发表时间: 2014-01-01
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Daniels, K. A.;Bastow, I. D.;Menand, T.
• 通讯作者: Menand, T.