Mudline from Mount St Helens lahar. Scientist examining the mudline (upper frame) left by one of the lahars (volcanic mud flows) that followed the eruption of Mount St Helens on 18 May 1980. Mount St Helens is in Washington State, USA. The lahars consisted of material from the collapse of the northern flank of the volcano, mixed with glacier ice, snow and meltwater from the eruption. Huge amounts (over 3 million cubic metres) of lahar material swept down the surrounding rivers for distances of nearly 30 kilometres. The mudline here is near the record height recorded for this eruption of 7.16 metres. Photographed on the Toutle River, near Interstate 5 bridge, Castle Rock, on 30 September 1980.