Monday, February 5, 2018

Kitsap Waterfall Survey: "Lower Lost Creek Cascades"

Well over a year since I've last surveyed a waterfall on the Kitsap Peninsula, this was a nice return to form. Several months ago, a friend of mine mentioned to me the existence of a small cascading type waterfall on Lost Creek within publicly accessible land. With me being busy at CWU, it was put on the back burner at the time. Not anymore, This past weekend (2/4/2018) I joined my friend, his son, and their dog and set out to document and photograph this cascade with my own eyes.

Our waterfalling dog companion, Delilah.
A half mile after it's opening fanfare, Lost Creek encounters another outcrop of Siletzia bedrock which underlies much of the Kitsap Peninsula. The canyon walls and creek bed become lined with a gorgeous blue-green-gray basaltic rock called gabbro. After tripping over a small rapid in the shadow of a massive fir stump, the creek flows around a bend and slides over a ten-foot drop into a beautifully secluded alcove with a surprisingly deep plunge pool.

The initial 10-foot drop of "Lower Lost Creek Cascades" 
Immediately after this drop, the creek narrows from 10 feet wide to less than 3 feet and careens through a narrow slot cut into the rock, dropping an additional 4 feet in the process. The force of the water tearing through this slot has drilled large circular potholes into the bedrock, making interesting shapes and formations.

Lost Creek tearing through the small defile, with several large potholes in the foreground
Immediately after the main slot, the creek funnels through another bottleneck in the rock in a slide 3 feet high slamming into a jutting rock, taking a 90-degree turn to the left and bouncing over a couple small drops, before leaping over a messy 5-foot rock face. This final drop ends in a rocky alcove similar to the large one upstream. Shortly downstream, "Lower Lost Creek Cascades" terminates in a final small 3-foot slide, bringing the total height to ~25 feet.

The bedrock lining the creekbed. 
The geology of the canyon here is both fascinating and stunning. The underlying grey-blue gabbro rock sets the tone, peppered with red-brown pieces of basalt, and cut with white veins of quartz and calcite. In quieter pools and gravel bars, occasional light colored granite clasts can be found from the overlying glacial debris mantling the entire peninsula. At least at one spot within the cascade, I found evidence for faulting and the intrusion of volcanic andesite dikes 50 million years ago. I plan to write posts on both those geologic stories in the near future.

Monday, January 22, 2018

Movie Monday: Seattle Fault-Nick on the Rocks

Here at CWU we have something of a rising celebrity. My advisor and professor Nick Zentner has begun a new small mini-series on KCTS this last year that discusses geologic stories within the Pacific Northwest. Season 2 just premiered this last Friday and it had an episode that, although brief, featured rocks from the Kitsap Peninsula. This episode discusses the threat of the Seattle Fault and the evidence we have for its existence. That evidence is the uplifted rocks of the Blakely Formation, exposed on Bainbridge Island and in South Kitsap, which I have discussed on this blog previously.

Without further ado, enjoy five minutes of Nick doing what he does best!

Tuesday, January 9, 2018

The Ellensburg Formation: A Distant Cousin to Kitsap's Blakely Formation.

It's been almost a year to the day since I've last posted. I hope to get a flow going again especially since I'm graduating this March. So here we go.

The Cascade volcanoes have been erupting for 40 million years, constructing massive volcanic edifices, ejecting clouds of debris and ash to rain down on eastern Washington, and sending mudflows and floods careening down river valleys into the Pacific Ocean, Puget Sound, and eastern lowlands. Today with the current position of our five active fire mountains, most, if not all lahars are directed to the west towards the Puget Sound with its heavily populated metropolitan centers, or south towards the Columbia River. Ten million years ago, the setting was slightly different. A volcano or a group of volcanoes near the present day location of White Pass were active, violently active. Explosive eruptions blasted frothy gas-rich magma out of their throats and sent moving masses of water, ash, and clay barrelling down ancient river valleys. One of these valleys was aimed toward the present day location of Thorp Washington. 

The Kittitas Valley with its modern-day volcanic sentinels Mount Adams (Left) and Mount Rainier (right). 
Driving east along Interstate 90 past Thorp one can look across the valley to the north and spot a group of imposing white cliffs towering over the adjacent fields. For a closer look, Highway 10 between Ellensburg and Thorp pass immediately below these cliffs. These are the "White Bluffs," and they are a geologic staple of the Kittitas Valley. These cliffs reveal a stack of 4-5 volcanic lahars produced by the volcanoes near White Pass so many millennia ago. The lahars appear as a solid white mass of ash-rich cement, suspending huge boulders of volcanic rock and peppered with sponge-like pumice, which is typically produced in significantly explosive eruptions. Each lahar is separated by beautifully structured river deposits, breaking down and depositing previous lahars and laying them down in organized and sorted beds and layers which flow and swirl, indicative of their slower process compared to the catastrophic volcanic apocalypses which ravaged the river valley half a dozen times. 

Outcrop of the "White Bluffs" showing a lahar (Thick layer at the base) and river deposits over top. 
This outcrop is just a small section of the Ellensburg Formation. This geologic formation can be found throughout the Kittitas and Yakima Valleys and varies significantly throughout its extent. Just southwest of Central Washington University's campus is "Craig's Hill," an elongated knoll in the middle of the city. This hill is completely composed of the Ellensburg Formation. However, it differs in composition from the "White Bluffs" in that there is only one volcanic lahar exposed, the majority of the hill is mostly a series of thick river rock deposits known as conglomerates. 

An exposed cliff face on Craig's Hill in Ellensburg showing it's large gravel deposits. 
The Ellensburg Formation's make up should sound familiar to readers, with its interwoven gravels, sandstones, and mudflows. It is, in fact, similar to the Blakely Formation, which lies around the shorelines of the Puget Sound and similarly records early volcanic activity in the Cascades. These two geologic cousins demonstrate how volcanism has been significantly affecting the state on both sides of the cascades for millions of years, and they will continue to do so for quite some time.