Findings: UK's coast with the most

九月 20, 2002

It was one of the world's largest submarine slides, and the waves it produced reached a height of 25m-30m above sea level in one inlet in the Shetland Islands.

The Storegga Slide, and the tsunami it generated, has been identified as one of the most significant natural disasters to strike the British Isles and Norway since the last ice age ended.

Yet scientists who have spent 15 years compiling the evidence have revealed a remarkably patchy impact on different stretches of coastline.

One site in Shetland was swamped by a vast wall of water, but other parts of Scotland would barely have noticed the event.

An estimated 1,700 km3 of seabed sediment, some in blocks up to 200m long, slipped across the Norwegian continental slope and onto the abyssal plain of the Norwegian Sea in the course of two days about 8,000 years ago. The tsunami this triggered ran into the Norwegian coast and the northern British Isles.

Earth scientists at Coventry University, led by Alastair and Sue Dawson, and at the University of Tromso, Norway, led by Stein Bondevik, have traced the tsunami's mark in Shetland.

They analysed sand deposits embedded in peat mosses or deposited in lakes after being washed inshore by the waves. Carbon dating has revealed the approximate time at which the sand was laid down and allowed a partial picture of the tsunami's impact to be painted.

Strong local and regional variation in the height of the waves has emerged from 30 such sites, showing the influence of coastal geography. The Shetland inlet where waves reached 25m-30m above sea level contrasts with other locations where the height has been put at 1m - almost invisible had the tide been out at the time.

The first human settlers were moving into Scotland at the time of the Storegga Slide, but there has been no evidence that any were caught in the catastrophe.

The latest results were presented at the Environmental Catastrophes and Recoveries in the Holocene Conference at Brunel University two weeks ago.

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