So, you've got a day to visit Mount St. Helens. Huzzah! All right, if you don't now, you will someday, quite possibly maybe, and you'll want to know how you can do All The Things when you haven't got much time. Never fear! In response to a request from Silver Fox, I'm putting together your very own field trip guide, which will show you things you can do in a day there, and feel you got your visit's worth. Keeping in mind, this is a Pacific Northwest summer day and so it is very, very long.
First, download Roadside Geology of Mount St. Helens National Volcanic Monument and Vicinity by Patrick Pringle. You can print it out or take it on a tablet, but don't leave home without it!
To whet your appetite, you can curl up with the field guide some weekend, and peruse these posts: Prelude to a Catastrophe: “The Current Quiet Interval Will Not Last…” and Prelude to a Catastrophe: “One of the Most Active and Most Explosive Volcanoes in the Cascade Range.”
Now that you're wound up and ready for adventure, start up Highway 504 - Spirit Lake Highway. Crusing along with a passenger who can read bits from Pringle's book, you'll see quite a lot of geology even before you get to our first stop - Mount St. Helens and the Toutle River Valley have a long history. Evidence of the area's dramatic past will pop out at you all the way along.
Optional beginning: Mount St. Helens Visitor Center at Silver Lake. For you strange people who like to get a super-early start, this is a nice place to get oriented. It's got many lovely displays, some handy and inexpensive guide books, and a great little walk along and over Silver Lake, which was created by a lahar that dammed Outlet Creek 2,500 years ago. On a clear day, you will have a lovely if distant view of Mount St. Helens, 30 miles up the valley.
If, on the other hand, you're driving in from Seattle, Portland or similar and arrive late in the morning, skip ahead to our first official stop.
Stop 1. Hoffstadt Viewpoint
Try to come hungry and arrive around 11 am, when the restaurant's open - I'm not kidding when I tell you they have the absolute best ranch I have ever tasted. And you'll want to be freshly fueled for the rest of the day. If you're here on a warm day, you can sit out on the deck, where misters will keep you cool, and this view up the Toutle River Valley will keep your eyes happy:
We're about 15 miles (25 kilometers) downstream from Mount St. Helens here. The Toutle River is a braided channel weaving its way through lots and lots of sediment, carrying lots and lots more sediment. If you've got sharp eyes, you'll see the remains of the N-1 dam, built to retain some of that sediment. Unfortunately, it failed to retain a rather large 1982 lahar, and winter storms and floods finished off what was left of it. A new, larger, and simply awesome sediment retention structure was built later (if you've got time left over, you can make a short side trip over to marvel at it - delightful little walk, nice engineering, and in certain seasons, you can nibble some delicious oxalis).
The remains of N-1 mark the edge of the debris avalanche, which we will be getting to know intimately later today. But most of what you're seeing here are older volcanics - Spud Mountain (the rather pointy peak in front of St. Helens in the above photo) and the other mountains hereabouts are far older than our active youngster - they're around 36 million years old, whereas St. Helens clocks in at around 40,000. You'll see the occasional bedrock outcrop. If you could get up there, you'd also find, somewhere beneath all the biology, evidence of glaciers that mantled this area, some of which came and went before the Puget Lobe of the Cordilleran Ice Sheet was so much as a gleam in the Cordilleran's ice. River terraces reveal evidence of pre-1980 lahars that roared down from the mountain in more recent times. Put it like this: this area has a long and exciting history, one that makes reading quad map documentation epic. Not even kidding.
Once you've had your fill of scenery, a short wander down a trail near the Visitor Center will take you to the Memorial Grove planted in memory of the people who died in the May 1980 eruption. Don't worry if you don't get a chance to pay your respects here - you'll get a second chance at the end of the trip.
When you continue on, you'll soon be entering the blast zone....
(Part II will be coming shortly - I'll not make you wait a whole week, my darlings!)
Decker, Barbara and Robert (2002): Road Guide to Mount St. Helens (Updated Edition). Double Decker Press.
Doukas, Michael P. (1990): Road Guide to Volcanic Deposits of Mount St. Helens and Vicinity, Washington. USGS Bulletin 1859.
Evarts, Russell C and Ashley, Roger P. (1992): Preliminary Geologic Map of the Elk Mountain Quadrangle, Cowlitz County, Washington. USGS Open-File Report 92-362.
Pringle, Patrick T. (2002): Roadside Geology of Mount St. Helens National Volcanic Monument and Vicinity. Washington DNR Information Circular 88.