But Mount St Helens showed that the coarse and fine material automatically separated into thin, distinct bands, demonstrating that such deposits can form very quickly from fast flowing fluids (liquids and gases).Since then, laboratory experiments have shown that fine laminae also form quickly from flowing water.
39(3):23-27June 2017 It was not until I visited Mount St Helens volcano in Washington State, USA, that I fully appreciated the immensity of its 1980 explosion.
You would expect a catastrophic, high speed ash flow to churn the fine particles and form a uniform, well-mixed deposit.
Thus, it had been conventionally thought that fine layers had to accumulate very slowly one upon the other over hundreds of years.
The Mount St Helens eruption also demonstrated how canyons can be formed much faster and in a different manner than conventionally thought.
Ongoing eruptions eroded the thick sediment dumped at the base of the volcano, producing multiple channels and canyons.All of this geological activity indicated that magma was rising up into the volcano. PDT) of May 18, 1980, a 5.1 magnitude earthquake struck and the bulging northern flank of the volcano collapsed along with the summit.