Field Trips

COGS offers a variety of field trips led by experts on Oregon's geology.


Geo-Explorations

Informal hikes, bike rides, and other explorations of geologically interesting sites.


To participate in field trips and geo-explorations:

  • You must be a member of COGS, or a guest of a member, to participate in field trips and geo-explorations.
  • You must sign the COGS field trip and geo-exploration waiver.
  • Please arrive at the meeting location 5-10 minutes early to get signed in.
  • Check the weather report and plan accordingly. Remember that weather conditions can change quickly in central Oregon! Dress in layers and wear sturdy hiking shoes.
  • Bring plenty of water and snacks, pack a lunch if specified in the field trip description.
  • Please leave your pets at home – dogs are not allowed on COGS field trips. 

    COGS Field Trip & Geo-Exploration Waiver


    Upcoming Field Trips

      • 1 Sep 2024
      • 1 Sep 2025
      • Various locations


      Citizen Science Opportunity!


      Are you interested in participating in a community sampling opportunity by taking a hike and collecting a rock? If so, then read on!


      The central Oregon Cascades are unusual when compared to the rest of the Cascade volcanic range. This region of the Cascades is dominated by basaltic andesite, a volcanic rock of intermediate composition between basalt and andesite. Basaltic andesite has been the most prevalent type of lava erupted in the central Oregon Cascades for the past ~8 million years. It can be seen in many of the prominent skyline peaks of central Oregon, including North Sister, Black Butte, Mt. Washington, and Three Fingered Jack.

      Despite the overwhelming dominance of basaltic andesite in this region, the chemical variability of these lavas has not been well documented. Are they related to basaltic lavas that have been erupted in the region? What geologic processes are responsible for generating and sustaining large volumes of basaltic andesite volcanism in this portion of the Cascades?


      Alyssa Smith, PhD candidate at Portland State University, is studying these rocks to improve understanding of their geochemistry and the volcanic history of the central Oregon Cascades.

      You can watch a recording of her recent COGS presentation here: On Basaltic Andesites: The Dominant Lava Type of the Central Oregon High Cascades


      Alyssa has been collecting samples from many locations in central Oregon, but more locations remain to be sampled. Knowing that many COGS members enjoy hiking and might be willing to carry a rock hammer, we have worked with to Alyssa to develop this community sampling opportunity. 



      Alyssa has assembled maps, a spreadsheet with sample locations, and tutorials on collection methods and how to use the Avenza Maps app in the field.These can be accessed in the following FOLDER

      So if you are going to hike Scott Mountain, or Black Crater, or one of the other 77 sites in Alyssa's field area, check out this citizen science opportunity. Contact Alyssa in advance of your hike to get all the details about how to collect samplesaks9@pdx.edu  

      With notice, a Zoom call with Alyssa can also be arranged.


      • 18 Oct 2024
      • 8:15 AM - 4:00 PM
      • Cascade Village Mall - between PetSmart & Ashleys Furniture
      • 2
      Register


      3-D perspective of bare-earth lidar data looking east towards Green Ridge with the Mile 29 Debris Flow on the left and Lower Bridge on the right click to expand


      Geo-Exploration: Head of the Metolius & Mile 29 Debris Flow

      Led by Bob Timmer & Bob Jensen

      October 18, 8:15 AM - 4:00 PM

      Registration opens October 11th; limited to 20 participants 

      This field trip will have two components, first a stop at the Head of the Metolius and then a 1-mile hike (2 miles round trip) along the Metolius to examine the Mile 29 Debris Flow. 

      Trip Itinerary

      Meet at Cascade Village Mall between PetSmart & Ashley Furniture @8:15AM to check-in and, optionally carpool. 

      Depart Bend @ 8:30AM from Cascade Village Mall

      Drive west on Highway 20, through Sisters, past Black Butte, and turn right on the Camp Sherman/ Metolius River Road.  Continue north for 2 1/2 miles to a "Y" and proceed right on Forest Service 14. Continue ~2 miles on FS 14 to the Head of the Metolius turn on the left. Proceed to the parking area. Restroom facilities 

      Stop 1 - Head of the Metolius

      We will walk 1/4 mile to the headwaters spring where the Metolius River emerges at the base of Black Butte. James et al. (2000) included the Metolius River headwaters spring in their analysis of groundwater flow in the Deschutes Basin using temperature, stable isotopes, and noble gases. This analysis showed that groundwater discharging at the Metolius headwater spring not only picks up geothermal heat along its flow path, but magmatic volatiles as well. Estimates of the age of the water varies from 47 to 120 years. The headwater spring was known for a relatively constant discharge of 100-125 cfs (Peterson & Groh, 1972). In August 2021, the Bend Bulletin reported, “In June 2018, the head of the Metolius had an outflow of 102 cfs. That dropped to 95.6 cfs in June 2019, 74 cfs in June 2020 and 55 cfs in August 2021”. Flow in September 2023 was reported at 47.9 cfs. Flow in the Metolius increases dramatically with input from springs and tributaries.  

      Return to cars and return to FS 14. Turn left and proceed to north on FS 14 for ~9 miles to the parking area on the east side of the Metolius at Lower Bridge.  

      Stop 2 - Lower Bridge parking area & hike to Mile 29 Debris Flow

      We will hike 3/4 mile downstream from the Lower Bridge Campground to a spot along the river for lunch. We will be hiking along a single-track, lightly maintained trail with small elevation changes. After lunch, we will hike another 1/4 mile on an unmaintained trail to the toe of the Mile 29 Debris Flow.

      Bare-earth lidar data of Mile 29 Debris Flow - click to enlarge

      THE MILE 29 DEBRIS FLOW -- WHAT HAPPENED?

      Larry Chitwood and Bob Jensen, Geologists

      Deschutes National Forest

      April 10, 1996

      At the height of the February Flood of 1996, a torrent of water and debris careened 3400 feet down a small canyon on Green Ridge. From the mouth of the canyon, an estimated 600,000 cubic feet (22,000 cubic yards) of debris-laden water shot across a gently-sloped, forested, alluvial fan at about 30 miles per hour. In thirty seconds the torrent reached the Metolius River at Mile 29 leaving in its wake a stark eight-acre field of boulders. About a dozen large trees survived the onslaught. Up to eight vertical feet of bark were battered away by rocks, and mud surged up the trunks leaving stains as high as 25 feet above the ground............

      There is more to the story.......which we will hear from Bob Jensen

      After examination of the toe, we will continue our view of the debris flow by walking cross-country  along the southern margin of the flow to Forest Service road 1499. We will then return to our vehicles with a 1-mile hike along FS 1499 to Lower Bridge.    

      Stop 3 - Down Canyon Viewpoint on FS 1490

      From Lower Bridge, retrace drive on FS 14 about 1/4 mile to FS 1490 on the left. Drive 2 miles up FS 1490 to "down canyon viewpoint". It is nearly impossible to appreciate the gradient of this canyon, and western slope of Green Ridge, until you stand at this viewpoint and look down the canyon. 

      Stop 4 - optional stop panoramic view across the basin

      Depending on time and weather, to drive a further mile up FS 1490 for a panoramic view  

      Return to Bend at 4:00PM

      Notes:

      • Please note that the weather is changing and getting COOLER
      • Please wear appropriate footwear for the hike, appropriate clothing and consider bringing hiking poles 
      • It is hunting season; the risk should be low due to the noise we will likely be making on the trail.
      • Bring a sack lunch and water
      • Please leave your dogs at home
      • Pit toilets are available at Metolius Headwaters and Lower Bridge Campground

    Past Field Trips

    13 Sep 2024 Alder Springs Geo-Exploration
    14 Jul 2024 Geology of Mount Bachelor and the Three Sisters Area
    7 Jul 2024 Three Fingered Jack Field Trip
    5 Jun 2024 Wildcat Caldera Field Trip
    19 Mar 2024 Second Session Added: Hydromagmatic Pinnacles of the Steelhead Falls Area Geo-Exploration
    14 Mar 2024 Hydromagmatic Pinnacles of the Steelhead Falls Area Geo-Exploration
    12 Nov 2023 Second Sesson Added: Fryrear Canyon Geo-Exploration II
    5 Nov 2023 Fryrear Canyon Geo-Exploration
    22 Sep 2023 Henkle Butte & Aspen Hollow Geo-Exploration
    22 Aug 2023 Tour Deschutes (River) Geohydrology Field Trip
    23 Jul 2023 Deschutes Formation Field Trip
    24 Jun 2023 Geohydrology of Siver Creek Field Trip, Harney Basin
    9 Jun 2023 Columbia Gorge Field Trip
    24 May 2023 Smith Rock Geo-Exploration
    26 Apr 2023 Session 2: Riley Ranch Field Trip
    21 Apr 2023 Riley Ranch Field Trip
    31 Mar 2023 Session 2: COGS Geo-Exploration: Barnes Butte, Prineville, OR
    31 Mar 2023 COGS Geo-Exploration: Barnes Butte, Prineville, OR
    12 Mar 2023 Steelhead Falls Geo-Exploration - Session 2
    11 Mar 2023 Steelhead Falls Geo-Exploration
    26 Oct 2022 Mafic Volcanism!
    30 Sep 2022 Thomas Condon Paleontology Center tour and field work experience
    17 Sep 2022 Deschutes Formation and Tumalo Volcanic Center Field Trip
    24 Aug 2022 Melting Glaciers, Failing Dams: The 1966 Debris Flow from No Name Lake Field Trip
    5 Aug 2022 Faults in the Strawberry Mountains
    1 Aug 2022 Whychus Creek Geo-Exploration
    26 Jun 2022 Lava Cast Forest Field Trip
    4 May 2022 COGS Geo-Exploration: Gray Butte
    7 Apr 2022 COGS Geo-Exploration: Barnes Butte, Prineville, OR
    3 Dec 2021 COGS Geo-Exploration: Farewell Bend Loop
    1 Dec 2021 COGS Geo-Exploration: Flatiron Rock in the Oregon Badlands
    6 Aug 2021 Ochoco Mining District Field Trip by Carrie Gordon & Derek Loeb
    28 Jul 2021 Deschutes River Geohydrology Field Trip
    27 Jun 2021 COGS Field Trip: Fault Scarps of Mt. Hood (south side)
    27 Mar 2020 Monthly Tours of the OSU-Cascades Pumice Mine
    4 Oct 2019 Deschutes River Field Trip
    14 Sep 2019 Mount Hood Field Trip
    22 Jul 2019 Newberry Volcano Field Trip
    13 Jul 2019 Wildcat Mountain Caldera Field Trip
    28 Jun 2019 Fire and Water: Recent mafic volcanism of the central Oregon Cascades
    16 May 2019 Geology of the Scout Camp loop trail along the middle Deschutes River
    27 Apr 2019 Geology of Shevlin Park
    3 Nov 2018 Hydrovolcanoes of Central Oregon Field Trip
    23 Oct 2018 Crooked River Caldera Field Trip
    23 Sep 2018 Mount Bachelor Volcanic Chain Field Trip
    14 Sep 2018 Clarno Fossil Beds Field Trip
    5 Aug 2018 Glacial Geomorphology of the Santiam Pass Area Field Trip
    14 Jul 2018 Lava Butte and Lava Lands Visitor Center
    10 May 2018 Deschutes Formation, Whychus Creek Geologic Field Trip
    1 Apr 2018 Geology of Riley Ranch Nature Reserve Field Trip

    Central Oregon Geoscience Society

    Email: COGeoSoc@gmail.com
    P.O. Box 2154,  Bend, Oregon 97709

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