Day 5 of the 2020 trip to Eastern Washington
/Carol Hasenberg, Past President of GSOC and current Field Trip Director, visited eastern Washington recently with her husband John. They based the trip primarily upon the geologic topics covered in the “Nick From Home” video series by CWU professor Nick Zentner. If you’ve come in through the back door, i.e., Facebook or some other link directly to this page, you may want to start at the introduction page to the trip.
Overview of Day 5.
It’s a new day dawning at Alta Lake SP.
This morning at 4:30 am I woke up to the sound, “Who-who-who, Who!, Who!”. This repeated four or five times. For sure it was an owl! A few minutes later I heard a couple of high nasal “Peent!” cries. As I lay there listening, I suddenly remembered that I had the Audubon app on my iPhone. Hoping there was internet access, I got out my phone, checked out the most likely candidates, and sure enough I had heard a great horned owl in the Ponderosa Pine forest at Alta Lake SP. The later call was that of a common nighthawk. Cool!
Sometime later I emerged from the tent to greet a lovely new day. At the start of this day, John and I had thought that we were going to head over to Icicle Gorge by Leavenworth and snag a campsite in one of the several national forest campgrounds over there before the weekenders arrived (it was Thursday). We were getting weary of camping, though. It had been very hot and dusty in all the campgrounds (except for the picnic areas) and there were lots of folks here at Alta who were not being very careful. The Alta Lake beach had been a complete zoo as well, so we drove right by without stopping. In addition, the weather forecast had indicated that it would get to 105 F in Wenatchee this day and 107 F the following day. With that in mind, we kept our options open. We drove down the west bank of the Columbia bound for the Lake Chelan area.
…and then we arrived at Lake Chelan.
Neither of us had visited Lake Chelan before this trip. I had been to the migmatite of the Chelan Complex with GSOC on the Wenatchee field trip of 2002, but we didn’t visit the lake, and I’d always heard how beautiful the lake was. Well, we got there on a fine hot day and stopped at a lakeside park to look at the water. The lake was so beautiful and the water so crystal clear! Well, that was a game-changer. I asked John, “Hey, why don’t we stay here for the night?” It did not take much convincing. We booked the last room in the beautiful lodge right by the park. My brain was already busy recomputing trip itineraries.
Lucy and I at Lake Chelan SP.
But just for the sake of completeness, before we confirmed the booking we drove over to Lake Chelan SP and checked out the camping scene. It was a total zoo. I don’t think that there was a single empty site, and it didn’t look like COVID-19 was a concern for any of the campers. We did stop at the lakefront away from the beach to take a photo. We decided that with a hotel room we’d at least have a bathroom to ourselves, and more importantly, AIR CONDITIONING!
With that business taken care of, we were free to explore. We decided that we could drive down the Columbia to Wenatchee on the east side and back to Chelan on the west side, seeing the sights, stopping at some of the parks and checking out the rocks. And what an interesting stretch of highway this is! We referenced Miller & Cowan’s Wenatchee-Pateros trip on US 97 (pg. 142), and the description of the route was “nearly all the bedrock exposed along the road belongs to terranes of the Crystalline Core of the North Cascades.” Yes!
Of course, we had been seeing the metamorphic rocks of the Chelan Complex all around the lake. But we’re getting ahead of ourselves here, because up in Chelan the star of the show is the lake itself. I recommend the Nick From Home Livestream #16 on this topic for a more in-depth treatment. The deep trough housing the lake was carved by two competing lobes of the Cordilleran Ice Sheet; the Skagit Lobe from the northwest coming down the valley and the Okanogan Lobe coming from the southeast going up the valley. The lake is very deep (1486’) and the lowest point is 388 feet below sea level! It’s about a mile wide and 50 miles long. The outlet to the valley was dammed by the glacial debris from the Okanogan Lobe. This was further augmented by the Washington Water Power Company in 1927 raising the lake level by 20’.
It’s only icing on the cake that the most interesting roadcut all along this stretch of road is the migmatite of the Chelan Complex that is exposed on the grade from Lake Chelan to the Columbia River at Chelan Falls. It’s striped, swirled, and even contains parts that look igneous (ie, unmetamorphosed). The rock metamorphosed in the late Cretaceous and this rock, along with the Entiat pluton, whose tonalite grades into the migmatite, represents the Chelan Mountains terrane along the Columbia.
Between Entiat and Wenatchee lies outcrops of another terrane, the Swakane Biotite Gneiss of the Swakane Terrane. This material is darker and more fractured than the other rocks along the river, but of a similar age. A large island of Swakane Biotite Gneiss called Turtle Island is found in the Columbia River north of Wenatchee due to an ancient landslide.
What lovely rocks we saw this day! We got back to our nice cool hotel room and prepared to get to Icicle Gorge the next day for a hike, then to overnight in Ellensburg, the heart of Zentner Country!
Click here for Day 6.
