Met Office scientists have been working with the Universities of Reading and Hertfordshire to gather comprehensive data about the potential danger to aircraft from the volcanic plume that has been emitted from the recent eruption of Eyjafjallajökull in Iceland.
The volcanic dust was measured using newly-developed probes that attach to meteorological balloons that can be used for measuring volcanic dust.
The weather balloon and probe was launched at 9 am on Monday morning and clearly showed a 600 m thick layer of dust at a height of 4km. The layer was found to contain highly abrasive dust particles, at concentrations of a third of a milligram of dust in each cubic metre. While the amount sounds small, a typical jet engine would ingest some 60 billion of these particles every second. 
Graphic showing the concentration of volcanic ash above Stranraer, Scotland at 9am on Monday 19th April. It shows the concentration of volcanic ash particles per cubic metre at a range of heights above the ground. The large peak shows a concentration of volcanic ash 600 metres thick at a height of 4km.
News Source: http://nds.coi.gov.uk/content/detail.aspx?NewsAreaId=2&ReleaseID=413106&SubjectId=2 Image source: http://nds.coi.gov.uk/imagelibrary/detail.aspx?NewsAreaId=28&MediaDetailsID=1803&SubjectId=35
