Washington State:
A Planetary Analogue in Flood Basalts and Flood Channels

Fall, 2002
Sep 20-26

Every five years, LPL organises a major, out-of-area fieldtrip. The first, to Yellowstone National Park, took place in 1997. This trip, the second long-range expedition, was directed to three targets in Washington State, Mt. St. Helens, Columbia River flood basalts, and the Channelled Scablands. The trip was led by Alfred McEwen, Vic Baker, and Laz Kesthelyi. Jason Barnes, Windy Jaeger, and Jani Radebaugh organised it all.

Jason, Ross, Oleg, Zi bi, Peter, and Ralph took pictures on our trip to Washington State.

Day 1

We met at the Delta counter in Tucson Airport at 5am. Those of us on the left side of the plane had great views of the Grand Canyon and the Cascade Range during the flight to Portland via Salt Lake City.

We then picked up our rental vehicles and drove north to Kelso, where we stocked up on groceries and tried to catch up on sleep.

Day 2

Our first stop was at the Forest Learning Center on the way up to Mt. St. Helens. From there we had a good look at the S. Toutle river and the way that the lahars and mud flows had filled up the pre-existing river channel. Rachel talked about volcanism in the Cascades Range, Jason discussed the ecological recovery after the Mt. St. Helens eruption, and Mike told us about the lahars (mudflows) that came out of Mt. St. Helens on May 18th, 1980.

Our next stop was at the Johnston Ridge Observatory, which has a great overview of the remains of Mt. St. Helens.

We had several talks. Rachel talked again, this time about the seismology of the 1980 eruption, Jim talked about debris flows, then Mandy, John, and Dave delved into the physics of volcanic eruptions.

Our final stop for the day was at the Hummocks Trail. More talks and yet another view of Mt. St. Helens. Pete and Matt Pasek waved the flag for chemistrywith talks about the impact of emissions on climate and the magma chemistry. We stayed the night in Kelso again.

Day 3

We stopped at the Bonneville Dam for talks by Sally on the Bonneville landslide and by Ralph on an eclectic mix of planetary hydroelectric power and salmon spawning.

En route to The Dalles, Ross took a small step away from spheroidal weathering to talk about jointing in basalts. Arriving at The Dalles, we saw a great exposure of pillow basalts, interpreted for us by Laz, and heard Jani talk about palagonite, a basaltic glass, on Earth and Mars.

The Maryhill stop included a good overlook of the Columbia river. Special guest Jim O'Connor gave an overview of the Missoula Flood that formed the Channelled Scablands.

Matt Chamberlain, Laz, and Adam talked about different aspects of flood basalts at the Rock Creek stop, aided by convenient road and railway cuts.

Finally we stopped at the Sand Station Recreation Center for a view of the Wallula Gap, sunset, and a few talks. We stayed the night in Kennewick.

Day 4

The first stop of the day was with special guest Steve Reidel at the Rattlesnake Mountain Observatory.

Windy and Zibi talked about folds and wrinkle ridges, then Joe Plassmann related the history of the Hanford Nuclear Reservation upon which we were standing.

We also visited Umtanum Ridge and the Sentinel Bluffs, where Steve Reidel led a discussion on the geology of the area.

After our stop at Gingko State Park, we stopped at some lava and lake sediments nearby. Abby petrified us with examples of petrified wood.

Our last stop of the day was at Frenchman Springs Coulee where we saw some spectacular flood basalt exposure and the results of the floods carving the coulee. Matt Tiscareno (Matt the Third in this sequence) told us about the hydrodynamics of forming channelled scabland by wave-vortex scouring. We stayed the night in Moses Lake.

Day 5

We stopped at a great overlook of West Bar and its giant current ripples, which Adina and Vic explained to us.

Whilst driving through the spectacular Moses Coulee, Brandon educated us on hanging valleys and other glacial features. As Dave knows, glaciers are more common in this part of the world than in the Southwest regions we usually visit.

Laz showed us the rubbly pahoehoe at Armour Draw.

Dry Falls was an excellent example of a flood-carved coulee, and offered a good view and a nice little visitor's center. Abby discussed the very strange rhinoceros mould and Jonathan the geology and history of Dry Falls.

We visited the rather basic (groan...) Soap Lake and listened to Oleg extoll the virtues of its extremophiles and their possible martian counterparts.

Our last stop of the day was at the Ephrata Gravel Fan. This is a good analogue for the Mars Pathfinder landing site and it hosted a fieldtrip for the Pathfinder Science Team in September 1995. Upon discovering this giant boulder, we clambered up it and posed for a group picture. Getting camera timers to work slowly enough and people to run quickly enough that everyone was facing the camera for the picture was quite a challenge... We stayed the night in Moses Lake again.

Day 6

The day began with Jason's presentation on loess deposits in Crab Creek. Moving along to Amphitheater Crater, Devon and Windy discussed the ring dykes there.

We had a hike through barbed wire, which only attacked Ralph, out to the outcrop at Marengo Siding where Jay then debated the pros and cons of how Lake Missoula ruptured and drained. By the wonders of civil engineering, a loess hill has been cut in two enabling us to l ook at a cross-section. Devon took this opportunity to talk about the formation of streamlined landforms.

Our final stop that day was at the quaintly-named "Hole in the Ground," which was very pretty. We stayed the night at Spokane.

Day 7

On the last day we stopped at Hangman Creek to look at the sediments. Note the expensive houses over the fresh cliff face. After lunch we caught our return flight from Spokane back to Tucson via Salt Lake City.

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Last Updated: 02 May 2003