Hike & Learn 2016 Coordinator Katie Boehnlein tells about the geology hike led by Jad D'Allura. You can use her notes when you next hike Greensprings Loop.
It was a chilly morning as we ascended into the clouds that cloaked the Greensprings Summit. Twenty of us stalwart hikers were in for a treat as Jad D’Allura, emeritus professor of Geology at SOU, led us along the Greensprings Loop trail and Pacific Crest Trail in a journey back in time to the Monument’s geologic beginnings.
As we climbed a slight incline through the fire forest of Douglas Fir, Snowberry, Trillium, and end-of-season Fawn Lilies, Jad helped us imagine the tumultuous events that created the bedrock upon which the Monument’s biodiversity has emerged. The west side of Greensprings Mountain, where we began our hike, was formed by volcanoes eons ago, but has since been eroded and covered by forest. We were lucky, at times, to see evidence of this geologic movement rising above the soft, needle-strewn trail. Just a mile or so into our walk, we could see a lava flow rising above to our right. We were amazed to hear that these remnants of the Western Cascades have been tilted 25° to the north-northeast! This is because Klamath Falls is actively (though gently) sinking off to the east as the Klamath-Siskiyou Mountains lift off to the west. The cooling fractures splitting the rock face into distinct bands were perfect for the littlest among us to climb up for a better view of the valley off in the distance.
Along many of the ins and outs of the Greensprings Trail, the landscape changes dramatically, from open slope to oak woodland to hardwood groves. The Monument is famous for this biodiversity, but through the eyes of geology, our multifaceted journey around Greensprings Mountain exists solely because of the diversity of rock types. These varied types of rock break down to form the diverse soils that host so many different kinds of flora and fauna.
The open oak woodlands show us distinctly how the volcanic bedrock has weathered dramatically downslope over the years. Picking up rocks off the trail, we can look for white crystals called plagioclase feldspars, which tell us that the magma in this area cooled slowly as it rose from the Earth’s core. Darker minerals, like the dark green augite, and later forming quartz crystals, are best seen under a hand held magnifier (loupe).
At our lunch spot at Hyatt Meadow, protected by Douglas Firs, we watched Keene Creek become sodden in the deepening mist and drizzle. We had progressed to the boundary of two rock formations, the Roxy Ann and Wasson Formations. The new rocks of the Wasson Formation presented themselves to us: soft, white rock littering the creek bed. We learned that these rocks were formed by solidified ash that billowed out of nearby vents 24 million years ago. Imagine standing in the way of molten clouds blowing by at 200 miles per hour!
Our hike ended at the then rain-soaked Little Hyatt Reservoir. The dramatic finale was climbing up a small rise to see columnar basalt formations that ring the edge of the water. Imaginations buzzing, we headed back to our cars to warm up, eyes now open to the ancient history always underfoot.