1. IMPACTS OF BASALTIC VOLCANISM ON INCISED FLUVIAL SYSTEMS DOES THE RIVER GIVE A DAM? Kyle House, Nevada Bureau of Mines and Geology Cooper Brossy, Fugro /WLA, Inc. Liz Safran, Lewis & Clark College Lisa Ely, Central Washington University Jim O’Connor, U.S. Geological Survey Owyhee River Interstate Geological Investigation Network
2. Goal of this talk Describe the characteristics of the response of the Owyhee River, OR to the incursion of voluminous basaltic lava flows. Thanks to input from NinadBondre Kathy Cashman Duane Champion Ryan Crow Natalia Deligne Cassie Fenton Nick Foit Gordon Grant Chris Henry Keith Howard Karl Karlstrom Caitlin Orem Shannon Othus Tabitha Prosser Terry Spell Brent Turrin
4. ‘When lava met valley’ Morphological effects Channel and valley re-paving River diversion / realignment Channel Blockage and damming
5. Intracanyon flows: ‘When lava met valley’ Hydrological effects / Ecological effects Hey, there’s a lake! What the…there’s no sediment! Uh-oh, the new dam is leaking! !
6. ‘When lava met valley’ Regional effects Master stream forced to cut lava for 10ks of years ‘Normal’ vertical and lateral erosion thwarted Huge rock and sediment pulse to manage Deceleration of landscape lowering
7. The Owyhee River Tributary to the Snake River Junction of Nevada, Oregon, and Idaho Drainage area 8600 sq. miles Bulk of watershed on volcanic plateau Miocene rhyolite lavas Dispersed lacustrine basins Mio-Pliocene plateau basalt Pliocene river canyon Plio-Pleistocene intra-canyon basalt flows (6-8) Idaho Oregon Nevada
8. Middle Owyhee River: Quaternary lava flows Many late Cenozoic flows on the plateau, but only 6 extensive and well-preserved Quaternary intracanyon flows at surface Greeley lava Qbg: .78 to 1.8 Ma Coffee Pot Qbcp < 7 ka Bogus Rim Qbr: 1.8 Ma Clarks Butte Qbc: 240 ka Rocky Butte Qbrb: 30 ka Saddle Butte Qbs:145 ka West Crater Qbw: 60 ka 10 km
12. Middle Owyhee River: Quaternary lava dams 6 principal intacanyon lava flows 5 extant lava dams / deltas Greeley Bar Qbg: .78 to 1.8 Ma Iron Point Qbcp < 7 ka Ryegrass Qbr: 1.8 Ma Sand Spring Qbc: 240 ka Granite Ck Qbrb: 30 ka Qbw: 60 ka Qbs:145 ka 10 km
29. West Crater lava dam lake seds Saddle Butte lava West Crater lava dam (60-80 ka) 47 ka 55 ka 25 m of lacustrine sediments with Cascadian tephra layers. Evidence for long-lived lake
31. The gift that keeps on giving:The lava-landslide link Lava flows in the Owyhee lead to landslides River diversion Undercutting Lateral Unloading Landslide-rebound Stratigraphic loading
43. Incision Rates at Dogleg Bend T5 Spillway 38.13 ka 50 T4 34.95 ka Meters above river surface 40 30 1 mm/yr 20 T3 T2 14.77 ka 11.1 ka 10 T3 T4 T5 T2
44. Thwarted Erosion That which may have transpired in absence of intracanyon lava flows What is the tangible influence of extrafluvial processes? What isn’t in the landscape because of this? From Hamblin, 1994