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.

非洲大陆沿着东非裂谷河流逐渐分裂，这是一系列3000公里的深盆地和侧翼山脉。这个过程最终可能导致新海洋的形成，但在数百万年的时间范围内。在北部埃塞俄比亚北部的远处凹陷中，地球最外壳是一个相对刚性的，〜150 km厚的构造板，已被拉伸并加热到破裂点。地球地幔的上升岩石部分融化，升起，然后冷却以形成新的海洋板块。如此之多，几乎已经形成了新的海洋。在这里，我们有前所未有的机会见证板岩破裂和熔融岩石上升的过程（岩浆）。通常，此过程发生在浅海内，或沿着既定的海底蔓延中心沿着海底深处；不过，在远处，我们实际上可以在该地区发生时行走。卫星对地球的观察表明，构造板平均平均移动非常缓慢：通常每年几厘米或指甲生长速度。然而，很有偶尔会突然发生大型运动，通常会带来毁灭性的后果。 2005年9月，一系列的裂缝沿着远处抑郁症的60公里段打开，因为盘子对将其拉开的力作出了灾难性的反应。大约一周的时间，裂谷拆开了8米，最多下降了1米。正如当地人所说的那样，一系列地震标志着9月26日的一块熔融岩石升起到地面，Ash将空气在当地的空气变暗了3天。同时，跟踪该区域的卫星表明，附近火山上方的表面沿着表面以下的裂痕注入岩浆时，岩浆被注入了多达3米。破裂的速度和巨大长度并不意外，但从未直接测量过。远处的抑郁症是如此热干燥，几乎没有植被掩盖其顶部表面暴露的火山和沉积岩。这也意味着我们可以使用卫星对其图像形象，并测量地球表面随着故障的移动而变化的方式，并且随着加压熔融岩石的浮力升起，并沿裂谷内部的裂缝长度向上移动。自第一次主要地震以来的九个月中，继续发生更大的表面变化，地震继续轰动地球和当地居民。我们提出了一组主要的实验，这些实验将使地球变形，地球磁场和电场以及岩浆运动和爆发的专家汇集到这个独特的自然实验室。在接下来的五年中，英国，埃塞俄比亚，美国和新西兰科学家团队将合作解决板块构造的基本问题：。盘子的不同层如何伸展？ 。熔融的岩石在哪里形成并形成新的海洋壳？ 。熔融岩石如何向上移动？卫星将从上方成像地球，传感器将记录从遥远和近地震以及自然磁信号的声波，以形象岩石层的厚度。我们还将收集和分析同一地区年轻火山的岩石成分。从时空和时间的组成变化中得出的地球历史将为我们提供有关何时以及多久发生的何时以及多久发生的线索 /将来可能再次发生。

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

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.

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.

First recorded eruption of Nabro volcano, Eritrea, 2011.

• 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