Mt. St. Helens and Canyon Formation


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Rapid Canyon Formation:

On March 19, 1982, another eruption took place

  • This generated an enormous mud flow
  • This created at least three canyons 100+ feet in depth 1

One canyon was carved out in the headwaters of the North Fork of the Toutle River Valley

  • It is so large that it is actually 1/40 the size of the Grand Canyon – and yet it was created in only 9 hours
  • Geologists have actually termed this the “Little Grand Canyon” 2

“Conventional wisdom” holds that canyons typically form over many many years

  • This one sure didn’t


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This of course says nothing about the enormous canyons that formed as a result of the pyroclastic flows and mudflows that took place right after the initial May 18, 1980 eruption

  • During the 5 months following the eruption, two enormous canyons formed on the mountain itself
  • The Step Canyon and Loowit Canyon both were carved through hundreds of feet of thick solid rock 3

This image is taken from Mt St Helens looking down on to the two canyons that were formed within months of the initial eruption

  • Step Canyon (the one with the creek on the left) reaches 700 feet in depth
  • Loowit Canyon is the one with the creek to the right 4


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Strikingly similar features are evidenced in the Grand Canyon

  • It makes you wonder just how long it might have taken such beautiful formations like this to develop