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 CollegeLisa Ely, Central Washington UniversityJim O’Connor, U.S. Geological Survey

Owyhee River Interstate Geological Investigation Network

Goal of this talkDescribe the characteristics of the response of the Owyhee River, OR to the incursion of voluminous basaltic lava flows.

Thanks to input fromNinad BondreKathy CashmanDuane ChampionRyan CrowNatalia DeligneCassie FentonNick FoitGordon Grant

Chris HenryKeith HowardKarl KarlstromCaitlin OremShannon OthusTabitha ProsserTerry SpellBrent Turrin

‘When lava met valley’

• Intracanyon lavas create extreme disruption of ‘normal’ fluvial processes

▫Geomorphic effects

▫Hydrological effects / Ecological effects

▫Regional landscape effects

‘When lava met valley’

Morphological effects

▫Channel and valley re-paving

▫River diversion / realignment

▫Channel Blockage and damming

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!

!

‘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

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)

Nevada

Oregon

Idaho

Middle Owyhee River: Quaternary lava flows

10 km

Saddle Butte Qbs:145 ka

Bogus Rim Qbr: 1.8 Ma

Greeley lavaQbg: .78 to 1.8 Ma

Clarks Butte Qbc: 240 ka

West Crater Qbw: 60 ka

Coffee Pot

Qbcp < 7 ka

Rocky Butte Qbrb: 30 ka

Many late Cenozoic flows on the

plateau, but only 6 extensive and

well-preserved Quaternary

intracanyon flows at surface

Re-Paving courtesy of Bogus Lavas

The Bogus Lava paleovalley: upstream view

Intracanyon lava flow stratigraphy: flow margins

Middle Owyhee River: Quaternary lava dams

10 km

Qbs:145 ka

Qbr: 1.8 Ma

Qbg: .78 to 1.8 Ma

Qbc: 240 ka

Qbw: 60 ka

Qbcp < 7 ka

Qbrb: 30 ka

Iron Point

Ryegrass

Sand Spring

Granite Ck

Greeley Bar6 principal intacanyon lava flows

5 extant lava dams / deltas

Saddle Butte Lava Dam

Hello, water? It’s me…lava!

Subaerial lava

Lava delta‘foresets’

Passage zone

Saddle Butte lava-water interaction features

40

m

Saddle Butte lava dam

Lava deltaDam Forebay

Fluvio-lacustrine sediments

landslide

Subaerial lava

Earlier advance

Greeley Bar lava dam

Bogus Rim lava

Greeley lava flow and lava delta

West Crater Lava Dam

West Crater lava dam stratigraphy

Saddle Butte lava

West Crater lava deltaFossil

tributaryPaleovalley divide

West Crater lava delta and fossil tributary

Lava dam models: Crow et al., 2008

Type section of lava dam failure?

Mile 192, Colorado River in Grand Canyon

Grand Canyon lava dam failure deposit

Grand Canyon lava dam failure deposit

Lava dam models: Crow et al., 2008

Owyhee lava dams

Spillway gravels on Bogus Lavas

Bogus Rim lava spillway gravels

human

Spillway Gravels, West Crater lava

Yep, that’s a fault

1400 sq. km

West Crater lava dam lake seds

West Crater lava dam (60-80 ka)Saddle Butte lava

55 ka47 ka

25 m of lacustrine sediments with Cascadian tephra layers. Evidence for long-lived lake

Lava Dam Longevity

Stream Power

Sed Q Water Q

Dam integrity

Emplacement

Vent site Entry site Dam site

Structure Scale

Why does the river give a dam?

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

West Crater Lava Margin FAIL

The Lava-Landslide Link

Valley wall landslide

Lavamargin landslide

IntracanyonLava flow

Capping basalt

Sediments

displace

ment

Displacement Undercutting ‘Rebound’ Lava Unloading

undercutting

unloading

Owyhee landslide dam breach

Fluvial Incision History: river scale

Cooper Brossy figure

Fluvial incision chronometers1.8 Ma

240 ka

70 ka

915 m

1146 m

972 m

930 m

Lava Flow profiles: Reach-scale

Meters

Met

ers

The Bogus Lava background rate

80 m

220 m

Long term incision rate from Bogus Rim lava

270 m in 1.8 Ma0.15 mm /yr

38.13 ka

34.95 ka

14.77 ka

T3 T2

T4

11.1 ka

T5

50

40

30

20

10

Met

ers

abo

ve r

iver

su

rfac

e

T5T2

T3 T4

Incision Rates at Dogleg BendSpillway

1 m

m/y

r

Thwarted Erosion

From Hamblin, 1994

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?