Geomorphological evidence towards a de‐glacial control on volcanism
Geomorphological evidence towards a de‐glacial control on volcanism
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冰川消融控制火山活动的地貌证据
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发表时间：
2009
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通讯作者：
Oliver J. Lowe
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作者：
J. Carrivick;A. Russell;E. L. Rushmer;F. Tweed;Phillip M. Marren;H. Deeming;Oliver J. Lowe
存在许多理论，概念和数值模型来控制火山活动，但地质证据很少。我们描述并解释了冰下火山活动的区域地形和地貌表达，即在冰岛的Kverkfjöll。该地区由一系列平行的冰川下喷发的火山机构组成，它们共同提供了出色的3D地质暴露。这些脊的方向是南北或沿着最可能的LGM冰缘后退线。我们结合联合收割机地形和地貌观测来解释火山活动在空间上的变化，并将其归因于末次冰期冰盖的衰退和向下消耗。具体来说，我们观察到枕状熔岩大厦的高度或体积没有空间模式，这表明末次冰期冰盖下的裂缝喷发在空间上具有相似的动态。然而，玻璃碎屑岩和玻璃凝灰岩矿床仅限于近端和高海拔位置。此外，侵蚀接触面使岩相分裂，玻璃凝灰岩断裂侵入。这些观测结果共同表明，随着覆盖在上面的冰盖变得越来越薄，火山活动变得更具爆炸性。火山活动似乎也已经“撤退”到Kverkfjöll中央火山。冰川溃决洪水或“jökulhlaups”在冰川消退期间很普遍，部分原因是由于高梯度基岩地形导致冰下融水无法蓄水。对于北方冰岛，我们提出的景观发展序列表明，在全新世期间有两次主要的冰川前进，其中至少一次在Kverkfjöll可能与火山活动和jökulhlaup相吻合。未来的工作应该着眼于建立一个绝对的测年控制和/或年表。版权所有© 2009约翰威利父子有限公司。
A number of theoretical, conceptual and numerical models exist for de‐glacial controls on volcanism, but geological evidence is scarce. We describe and explain a regional topographic and geomorphic expression of sub‐glacial volcanism, namely that at Kverkfjöll, Iceland. This area comprises a series of parallel sub‐glacially‐erupted volcanic edifices, which together give excellent 3D geological exposure. These ridges are orientated north‐south or along the most probable line of LGM ice margin retreat. We combine topographic and geomorphic observations to explain the changing style of volcanism in space, and attribute this to the recession and downwasting of the LGM ice sheet. Specifically, we observe that there is no spatial pattern to pillow lava edifice heights or volumes, indicating that fissure eruptions beneath the LGM ice sheet were of similar dynamics in space. However, hyaloclastite and hyalotuff deposits are restricted to proximal and high elevation positions. Furthermore, lithofacies are split by erosional contacts and hyalotuffs are faulted and intruded. These observations together suggest that as the overlying ice sheet became thinner volcanic activity became more explosive. Volcanic activity also appears to have ‘retreated’ towards the Kverkfjöll central volcano. Glacial outburst floods or ‘jökulhlaups’ were prevalent during de‐glaciation, partly because sub‐glacial meltwater could not be impounded due to the high gradient bedrock topography. For northern Iceland, our proposed sequence of landscape development suggests two major glacial advances during the Holocene, at least one of which at Kverkfjöll probably coincided with volcanic activity and a jökulhlaup. Future work should look to establish an absolute dating control and/or chronology. Copyright © 2009 John Wiley & Sons, Ltd.