The effects of volcanic ash fall (tephra) on road and airport surfaces

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Nairn, I.A. 2002 The effects of volcanic ash fall (tephra) on road and airport surfaces . Lower Hutt: Institute of Geological & Nuclear Sciences. Institute of Geological & Nuclear Sciences science report 2002/13 32 p.

Abstract: The impacts of volcanic ash (tephra) falls on roads and airports have been documented in recent eruptions at Sakurajima (1955-), at Mt St Helens (1980), Pinatubo (1991), Rabaul (1994-), and to a minor extent, in New Zealand during the 1995 and 1996 Ruapehu eruptions. These observations provide valuable insights into the impacts of future distal (widespread) ash falls during New Zealand eruptions, and of the clean-up techniques available to recover from those impacts. A comparison of the recent observed eruptions with those known to have occurred in New Zealand over the last 2000 years shows that future eruptions here may be larger and more damaging than the recent observed events. Analysis of samples from post-2 ka New Zealand tephra deposits shows that these exhibit a wide range of deposit thickness (metres to mm), grain sizes (centimetres to microns), and clast types (scoria, pumice, lava, lithics, crystals). These variations occur both between the deposits of different eruptions, and laterally and vertically within the deposits of a single eruption. This diversity means that distal ash fall from a future eruption may produce effects rather different from the recent Ruapehu and overseas eruptions. Contingency planning for coping with a future eruption must consider a range of potential ashfall scenarios, each capable of producing ash deposits with a wide variety of possible compositions and engineering properties. (auth)