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|May 2019 — Central Oregon Geology Tour|
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Copyright © 2015 - 2022 Larrie Easterly
About 36 million years ago the cascade mountain range started to push up from the earths surface changing the central Oregon semi tropical forests and lakes into a dry arid semi desert region that was covered with multiple lava flows. Eventually things calmed down leaving unique geological features that can be experienced today with a bit of planning and lots of driving on gravel and dirt roads.
Last year on the Steens Mountain trip several of my friends from out of state asked if I knew the area east of Bend. I said yes. In the months that followed we stayed in touch and developed a five day tour that would take us to some of the unique geological features in Central Oregon. The trip was posted on the Expedition Portal and Overland Bound forums to see if anyone else was interested in traveling with us. The dates were set for May 23rd to the 27th with a meeting time of noon at the gas station and store in Riley, Oregon.
On Wednesday the 22nd I headed east towards Chickahominy Reservoir a few miles east of Riley. The reservoir was constructed in the 1950’s to manage runoff from the Potato Hills and Dry Mountain. It provides irrigation for farms and water for livestock in the area. The campground has shoreline sites as well as inland sites. The reservoir is stocked with rainbow trout and is a popular fishing spot. Like most of Central Oregon the afternoon was quite windy. It took me some time to get the van oriented correctly to block the wind from the picnic table. The campground is maintained by the Bureau of Land Management (BLM). There is a fee for camping at some BLM campsites like Chickahominy. I forgot to bring small bills or my check book so I needed to make a run into Riley to get change so I could pay the fee.
Chickahominy Reservoir — Photo Galley
The next morning a walk along the shoreline brought me to a number of singing birds and beautiful wildflowers. After the walk it was time to head for Riley to meet up with the rest of the group. Introductions were made, gas and supplies were purchased, and time was spent getting to know each other and discussing the route over lunch.
The Travelers — Photo Galley
Our first stop was Glass Buttes. Located about 30 miles west of Riley the buttes are a series of mountains the tallest of which rises above the desert floor to a height of 6,400 feet. The three mile road into the area is very rough and prone to be slippery after a rain storm. There are several free campsites in the area.
Glass Buttes gets its name from the large amounts of obsidian in the area. There is so much obsidian that the BLM allows you to take up to 250 pounds of it home with your each year. There are about nine different colors of obsidian that can be found in the area. Serious rock hounders dig to find the colors that they want. The average person that just wants a few souvenirs can walk the along roads or the through the sagebrush and pick up pieces that were turned up by the road grader or just lying on the ground.
After collecting some obsidian we continued west and turned on to all gravel Fredricks Butte Road where we aired down our tires. We headed south to the Lost Forest and Christmas Valley Sand Dunes. We would spend the next three days driving on on a mix of dirt and gravel roads. Fredricks Butte Road is one of the main north/south roads to Christmas Valley to the Central Oregon Highway. It is heavily traveled by trucks hauling hay and other commodities that are grown in the area. If you drive the road be sure to watch for oncoming dust clouds that indicate an oncoming vehicle.
Lost Forest Research Natural Area is an ancient ponderosa pine forest. It is the remains of a forest that existed in a cooler and wetter time period. The trees managed to adapt to the changing climate that occurred over the past 3,200 years. The forest is about 40 miles from the closest other ponderosa pines in the Deschutes National Forest. Camping is allowed in designated areas only. It is weird to see the pines growing out of the desert sand.
The Christmas Valley Sand Dunes is just south of the Lost Forest. It is designated as an Area of Critical Environmental Concern (ACEC). The dunes are 60 feet tall and is the largest inland shifting sand dune system in the Pacific Northwest. When Mount Mazama exploded 7,000 years ago, creating Crater Lake, much of the ash and pumice from the eruption landed in what is now the Christmas Valley area. The winds gathered the ash and pumice to create the sand dunes. The dunes are a popular destination for off-highway vehicle enthusiasts with nearly 8,900 acres of the Sand Dunes are open to vehicles.
George, Chad, Bob and his daughters took some time to drive around the dunes while the rest of us made dinner and relaxed around the campfire. They had a great time. Due to all of the snow and rain this winter in Central Oregon the fire season had not yet started. This was the first time in many years that we could sit around a campfire on Memorial Day weekend.
Christmas Valley is a small town in Central Oregon where we stopped for snacks and fuel before continuing north to Crack in the Ground. Gas prices were close to those in Bend. There was a bake sale at the store where I bought a loaf of banana bread. It was quite good.
Crack in the Ground is just what the name implies. A volcanic fissure that is two miles long and 70 feet deep. There are actually several parallel cracks next to each other. One has hiking trail along its bottom. The others are to narrow to walk through. In the summer the temperatures at the bottom of the crack can be 20F degrees cooler that at the top.
Crack in the Ground — Photo Galley
A few miles north of Crack in the Ground is Green Mountain Lookout. The fire lookout was not open for the season yet so we stopped at the campground for lunch. The views of the surround valleys from the top of the mountain are spectacular. We could just make out some of the mountains in the snow capped Cascade Range about 70 miles away.
Our next stop was Derrick Cave. Located at the southern edge of the Deschutes National Forest. The cave is not the easiest place to get to from the south. The Forest Service’s recommended route backtracks from Crack in the Ground to Fort Rock and then north then east then south. This roundabout route is required as the direct route north from Crack in the Ground crosses private land. On a previous trip to Derrick Cave I knew it was possible to follow some of the rough dirt tracks across the desert from Green Mountain Lookout north then west to the cave. The route requires good planning, maps, a high clearance 4x4 with good tires and lots of time and patience.
Derrick Cave — Photo Galley
Derrick Cave is a lava tube 30 feet high, 50 feet wide and 1/4 mile long. The cave developed just south of the main vent for the Devils Garden lava flows and was the route of most of the lava which spread south from the vent across the desert. In the 1960s, Derrick Cave was a designated nuclear fallout shelter that was stocked with supplies for several thousand people. Exactly how they would have transported the people from Bend to the cave is a mystery to me.
The last stop of the day was at the largest juniper tree in Oregon. There is not much information available about this tree on the web You have to go there to see it for yourself, it is very impressive.
Derrick Cave — Photo Galley
We did to want to create a new fire pit and camping ares so searched around and found an old partially buried fire pit down the road from the juniper tree for our second nights camping spot. While we were setting up camp we were serenaded by a nearby pack coyotes. Later that night we heard them again. While out walking Kitt found an old Upper 10 soda bottle that was in good condition. We think the bottle dates from the 40s or 50s and had probably been lying in that spot since then.
There was early morning frost and clear skies when we awoke the next morning. After breakfast and packing up we headed west through the forest and then south towards Fort Rock.
Fort Rock is a tuff ring volcano. It towered over the ice age lake that covered the Christmas Valley area. The ring is about 4,460 feet in diameter and stands about 200 feet above the surrounding plain. The site is a state natural area.
After climbing up to the view point and walking the trails at Fort Rock we headed for Hole in the Ground. The name says it all, it is a one mile diameter 490 feet deep hole in the ground. It was formed by multiple volcanic explosions about 13,000 to 18,000 years ago. The explosions threw huge blocks of stone as far as 2.3 miles from the crater.
Fort Rock — Photo Galley
A few miles a way is another explosion crater or maar called Big Hole. This one is older and larger, 6,000 ft across and 300 feet deep, than Hole in the Ground. It is estimated to be at least 20,000 years old. It is definitely not as impressive as Hole in the Ground as it is covered with trees so it is hard to appreciate its size and shape.
Prior to the trip Kitt asked if he should bring a chainsaw along. After discussing it for a bit we decided that it would be a good idea to bring it. We were about half way around the narrow Big Hole access road when we came across two downed trees that blocked our route. We were glad we had the saw with us. Backing out of our location would have been very difficult.
From Big Hole we worked our way north through the Deschutes NF heading towards Arnold Ice Cave. It took longer to wind our way through the network of forest service roads than we expected. Some of the roads were gravel others were rough dirt two tracks with pine trees growing at the very edge of the track making for slow going. It looked like some of the roads had not been driven on in quite a while.
As we were traveling along one of the roads we saw that unlike most of the roads we traveled this one was raised above the surround grade level and was at a very even slope. After a while we realized that we were on an old railroad grade.
By about 4:00 pm were were still about an hour away from the cave. We made the turn around a butte and came to a wonderful camping area. It was like a park with tall pine trees, a large fire pit and lots of space to park our rigs on the grass. It was an easy decision to spend the night in this idilic location. We all enjoyed the sound of the wind in the pines.
After a good nights sleep we continued our journey to Arnold Ice Cave. As we got closer to the cave we drove into the clouds. Visibility was limited to less than 100 yards. We were all glad to safely arrive at the cave.
Arnold Ice Cave — Photo Galley
The cave system is actually an old lava tube system that is approximately 80,000 years old. It got its name from the ice that use to fill it. The ice was mined in the 50s and taken to Bend. There is still debris from the mining operation in the cave. There are 19 caves in the area that measure 4.5 miles from end-to-end, and most are only a few hundred feet deep. The largest cave is closed to the public to protect the bat population that lives there.
We backtracked a bit to the Central Oregon Highway. Just before the entrance to the highway we stopped and aired up our tires for the trip to Prineville where we had lunch. Continuing north and a bit east we headed to the Painted Hills.
The yellows, golds, blacks, and reds of the Painted Hills are beautiful and an amazing expanse of color. The colors represent different geological periods of history. The red is laterite soil from a time when it was warm and humid. The gray is mudstone, siltstone, and shale. Black is lignite that used to be plant life.
Painted Hills — Photo Galley
Our campsite that night was next to a fast flowing creek. The rain did not deter us from having a good time around our campfire.
The morning of our last day we headed east to the Thomas Condon Paleontology and Visitor Center at the John Day Fossil Beds. The center has an amazing display of fossils from the area. Fossils have been extracted from the beds since the 19th century. They continue to find new fossils today.
Skull Fossil — Photo Galley
After touring the center it was time to say goodby to new friends and head home. It was a good trip and I look forward to the next one.
Lessons Learned Bring small bills or my checkbook to pay the fee at BLM and Forest Service campsites. It is hard to watch the GPS track on an iPad and the road at the same time.
Statistics Total miles from home and back: 1,175 Gravel/dirt road miles from Riley to the Central Oregon Highway: 240 Fuel used: 101 gallons Average MPG: 11.6
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