Dambusters
Abstract Charles Lyell, following the original idea of Robert Hooke, believed that only earthquakes accompanied land uplift. However, after hearing persistent stories that there was long-term aseismic uplift proceeding around the coasts of the Gulf of Bothnia, in 1835 he made a visit to Sweden and r...
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| Format: | Book Part |
| Language: | English |
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Oxford University PressOxford
2024
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| Online Access: | http://dx.doi.org/10.1093/oso/9780198871620.003.0009 https://academic.oup.com/book/chapter-pdf/58292317/oso-9780198871620-chapter-9.pdf |
| Summary: | Abstract Charles Lyell, following the original idea of Robert Hooke, believed that only earthquakes accompanied land uplift. However, after hearing persistent stories that there was long-term aseismic uplift proceeding around the coasts of the Gulf of Bothnia, in 1835 he made a visit to Sweden and returned convinced that uplift was in fact proceeding at up to 10mm per year. The explanation for this only emerged towards the end of the 19th century – that a former ice sheet, more than a kilometre thick had weighed down on the mantle and that we were now observing the recovery of a bowl of subsidence. Over the past 2,5 million years of the Pleistocene, there have been a succession of ice ages and ice sheet advances across the North Sea and all down the Hebrides and the Irish Sea. These ice advances have transformed the landscape principally by blocking rivers passing to the north and east, creating vast lakes that have then eroded new outlets to the south and west. By this means, the Thames River formerly began in west Wales, but its headwaters were captured by the River Severn. The largest of all these transformations was in the southern North Sea four hundred and fifty thousand years ago. An ice-dammed lake developed in which water levels rose to more than 30 metres above sea-level before flowing over the hills that ran between Kent and France, creating enormous waterfalls that carved great chasms down to 140m below sea-level and opening what was at first a gorge that soon widened into the Straits of Dover. In northern Scandinavia a series of great earthquakes, leaving prominent fault scarps happened as the ice receded, probably triggering the collapse of the continental shelf margin of mid-Norway generating a tsunami that was at its highest in the Shetlands and west Norway. |
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