This post covers Day 2 of the Annual Twin Camping Trip: for Day 1 check out Smith Rock Hike: Volcanic Rocks, Volcanic Heat.
Heather and I woke up bright and early on a chilly morning to get a head start on the popular Green Lakes trail up to the base of South Sister, one of a trio of snow-capped volcanic peaks west of Bend. We hiked Trail 1.7 (traced in yellow on the map below), and stopped for lunch at a very scenic overlook (red dot). Including all our side jaunts, it was a 11 mile round-trip hike with about 1,000 feet of elevation gain from the trailhead to the lakes. We were three thousand feet higher here than at Smith Rock, so thankfully it was much cooler.
Fall Creek is aptly named – and it’s absolutely beautiful!
Just when the ponderosa pines and waterfalls are starting to become routine, the view opens up onto the jagged slopes of the Newberry rhyolitic dome from South Sister’s most recent eruption 2,000 years ago. Although it looks inhospitable it actually is a perfect home for a variety of adorable rodents. A little pika and several yellow-bellied marmots stuck their noses out of the rubble to say hello. Too far away to photograph, alas, you’ll just have to take our word for it. Heather said that the lava flow looked like Mordor from the Lord of the Rings… maybe a lair for the ASBOG Balrog?
These lava flows blocked the Fall Creek drainage thoroughly enough that debris and water built up behind them, creating the spectacular Green Lakes!
As we sat to eat lunch at the overlook we were entertained by the profanity yelled by hikers who decided to gleefully jump into Green Lake only to discover how freezing cold it is, even in August. Let’s just say that when I stuck my feet in the lake to cool off it only took about 10 seconds for them to go numb… I’m not tempted to turn that into a full-body experience.
We were pretty beat by the time we descended back to the trailhead and happily fell into our hammocks with libations back at Elk Lake. It was another hour or two before we felt like moving again, and we made dinner with the last bits of daylight. Afterwards we took advantage of the clear skies to stargaze – Heather had never seen the Milky Way except in photos. Stupid southeast/east coast light pollution. I’m so glad we could fix that – we had an amazing view not only of our galaxy but of several shooting stars that put on a show! The next morning we packed up camp and headed out on the next adventure to an even bigger volcano: Crater Lake National Park.
But before we leave the Sisters… what were we hiking on?
All three Sisters are part of the High Cascades, the range of distinctive volcanoes in Oregon and Washington that formed between approximately 35 million years ago and the present. I gave a bit of a teaser to their history in my post about Dome Rock in the Western Cascades – I could see the Sisters from there.
The Sisters, while linked together by their names, are not triplets. North Sister is by far the eldest; it was formed between 120,000 to 45,000 years ago by basalt and andesite lavas and eruptions. Middle Sister formed between 40 and 14 thousand years ago, but primarily between 25 and 18 thousand years ago, putting it close in age with South Sister. It is built of andesite, dacite, and rhyolite, and is famous for the archaeologically significant Obsidian Cliffs formed in one of its eruptions that became a tool-making bonanza for Native Americans.
Here’s more specific timeline that I drew for South Sister, based on information from the US Geological Survey Volcanic Hazards Program (USGS VHP).
You can get an idea of the wide range of eruption ages in the figure below from the Oregon Department of Geology and Mineral Industries (DOGAMI)’s recreation brochure for the area.
While South Sister hasn’t erupted in two thousand years and the Middle and North Sisters have been dormant even longer, the USGS isn’t ruling out future eruptions.
“The Three Sisters region has hosted volcanic eruptions for hundreds of thousands of years, and future eruptions are a certainty. Two types of volcanoes exist in the region and each poses different hazards. South and Middle Sister are recurrently active over thousands to tens of thousands of years and may either erupt explosively or produce substantial lava domes that could collapse into pyroclastic flows. They could also produce lava flows. In contrast, less explosive eruptions could occur almost anywhere in the surrounding area, and construct small cinder cones to large shield volcanoes made mostly of basalt to andesite lava flows. These volcanoes are typically short-lived (months to centuries) and usually don’t erupt again”
If it’s any reassurance, geologists’ ideas of “a certainty” consider a geologic-scaled timeline up to thousands of years…. so life near the Sisters could well be mercifully boring during our lifetimes.
The hiking here, however, is anything but!
USGS Volcanic hazards page for South Sister: https://volcanoes.usgs.gov/volcanoes/three_sisters/three_sisters_geo_hist_128.html
USGS VHP page for all Three Sisters: https://volcanoes.usgs.gov/volcanoes/three_sisters/geo_hist_south_sister.html
DOGAMI flier for Three Sisters: https://www.oregongeology.org/pubs/ll/LL-ThreeSistersRecMap.pdf
In the Playground of Giants Green Lake Field Guide http://intheplaygroundofgiants.com/field-guides-to-central-oregons-geology/field-guide-to-the-cascade-lakes-and-willamette-pass-areas/two-can-tango-recent-and-ongoing-volcanism-and-glaciation-in-the-cascade-lakes-area-field-trip-2a/optional-hiking-trails-for-field-trip-2a/
(Marmot) By Diliff – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=26414860
Many thanks to Heather van Stolk!!