Javaria Aziz
Registration Opens June 28 at 7:00 AM
Three Fingered Jack Field Trip
Led by Javaria Aziz
July 7, 9:00 AM - 5 PM
Join Javaria Aziz, masters degree student at Portland State University and a 2023 recipient of a COGS research grant, for a field trip focused on her field area at Three Fingered Jack.
Hike distance: ~7 miles out and back with 1400 ft elevation gain.
Description: The central High Cascades graben has been the center of mafic volcanism with ∼60 km3 of lava erupting from scoria cones and mafic composite cones in the past 15,000 years. One of these mafic composite cones is Three Fingered Jack, located south of Mount Jefferson, near the town of Sisters, Oregon. Three Fingered Jack is composed of porphyritic calc-alkaline basaltic andesite lava flows, with up to 3mm plagioclase and olivine phenocrysts. It has been deeply dissected from glaciation, exposing much of its eruptive stratigraphy. Complete sequences of stacked, thin lava flows, are exposed on the southern and eastern flanks. The core of the edifice is highly stratified with layers of pyroclastic flows, scoria deposits and lava flows. The edifice core is cut by numerous dikes that are fed from intrusive plugs. This field trip will explore the eruptive products of Three Fingered Jack and discuss the changes in lava composition from a regional perspective.
This field trip takes place in the Mt. Jefferson Wilderness and there is a hard limit on group size of 12. Please note that in addition to distance and elevation gain listed above, the trail is likely to have residual snow is some spots and some downed trees that will increase the difficulty. There will also likely be mosquitoes present and they apparently do not abide by the limits on group size!
Initial meetup location will be at the Sisters Ranger District office in Sisters ( 201 N Pine St, Sisters, OR 97759 ). A location to meet for ride sharing or caravaning from Bend will be arranged. If you are coming from points west of Sisters an additional meetup location can be arranged. Per COGS policy, ride sharing is completely voluntary but it is encouraged because of limited parking and the long and usually rough dirt road. Please contact Derek Loeb at DerekLoeb@gmail.com with questions?
Please note that this event is limited to 12 participants and registration must be done via the registration button on the trip listing on the COGS website. Successful registration will be confirmed on the webpage by a light green box indicating registration was successful and by a confirmation email. If you don't get this email you should try the registration process again.
