Currently browsing tag

landscape evolution

The Hydrology and Evolution of Basaltic Landscapes: Notes from GSA Sunday

This post is cross-posted at Highly Allochthonous. Please look over there for any comments.


Like many North American geobloggers, I’ve recently returned from the Geological Society of America meeting in Portland, Oregon. It was a bittersweet trip for me, as it was a return to my spiritual homeland, where I spent five happy years working on the rocks and waters of the Cascade Range. Since then, I’ve felt a bit exiled on the Eastern Seaboard, so it was perhaps apropos that the trip back was a bit of a tease…in my four days in Oregon, I did not manage to see a single mountain. The picture to the right is the Hood River, draining the north side of Mt. Hood, about 45 minutes east of Portland. It was taken in April 2007, during field work for my post-doc.

Sunday

After an unexpectedly long layover in Phoenix and an entirely unexpected layover in San Francisco (thank you, US Airways), I arrived in Portland at 1 am local time Sunday morning. With any potential time-change/jet-lag problems thus mitigated, I arrived bright eyed for the first talks on Sunday morning.

The main order of business on Sunday morning was the Pardee Keynote Symposium on “The Evolution of Basaltic Landscapes: Time and River and the Lava Flowing.” I arrived in time to hear a fascinating talk on “Impacts of basaltic volcanism on incised fluvial systems: does the river give a dam?” by blogger/tweep/mapper extraordinaire Kyle House. He was talking about the lava dams, debris flows, and river incision of the Owyhee River of eastern Oregon. After a few gorgeous photos accompanied magnificent Lidar images, I was thoroughly convinced of the utility of Lidar for high-resolution geological mapping. I was also salivating at the thought of a whole day of water + lava talks full of gorgeous volcano photos.

After Steve Ingebritsen gave a lovely overview of the hydrogeology of basalts, Dennis Geist convinced me that I absolutely have to go to the Galapagos Islands, by showing pictures of volcanoes with whales for scale. His talk focused on the connections between geology and biology in the Galapagos, and got me thinking about the implications of volcanic emergence and subsidence for the evolution of the creatures of the famous archipelago. While Geist tried to convince his audience that the vegetation of the Galapagos is supported with basically no soil, neither I nor the next speaker, Oliver Chadwick, quite believed him on that point.

Indeed Chadwick talked about the patterns and processes of soil development on basaltic landscapes, where weathering rates depend not only on the usual climatic factors but also on the flow texture – with aa and pahoehoe flows exhibitting different patterns and timescales of soil development. For my own work, one key point that Chadwick made was “At some point in the history of lava flows, the surface becomes less permeable than the whole…” I think that statement has implications for the way we think about drainage development in basaltic landscapes, but I’ll wait to say more about that until my publication and/or funding record bear me out.

I spent my afternoon thinking more about basalt hydrology, in a session on “Hydrologic Characterization and Simulation of Neogene Volcanic Terranes.” I’ve got lots of notes from that session that are probably of interest only to me, but I will say that it was exciting to hear one of the grad student speakers say to me “I’ve been reading your dissertation” and to hear my work cited more than once. It is such a relief to know that people working in the field actually find my work interesting or useful. Towards the end of the session, I gave a talk on the geomorphic and hydrologic co-evolution of the central Oregon Cascades Range. My talk was based on a paper that has undergone several major revisions since my Ph.D. days, and it was a pleasure to share the latest and greatest incarnation of my thinking on the subject. The pleasure was immeasurably increased by a recent letter from the journal editor giving me only very minor revisions to do before acceptance.

On Sunday evening, the attendees of the morning talks reconvened for a wine tasting with a geological theme – the terroir of taste of Oregon wines grown on basalt versus sandstone. The wine was donated by Willamette Valley Vineyards (basalt) and King Estate (sandstone), and we got to hear from the wine makers as we sipped their wares. According to them, if you see a 2008 Willamette Valley appellation Pinot Noir or Pinot Gris, snap it up. They reckon it will be the best year ever for Oregon wines. That’s saying quite a bit, since Oregon is consistently recognized as one of the world’s best Pinot producing regions.

After a day of stimulating talks and invigorating conversation, I was ready to dive into two days focused on groundwater-surface water interactions and a day of snow, mega-floods, and debris flows to round out my conference. But my notes on those days will have to wait for now, as those paper revisions are not taking care of themselves.

GSA Abstract: On a template set by basalt flows, hydrology and erosional topography coevolve in the Oregon Cascade Range

The Watershed Hydrogeology Lab is going to be busy at this year’s Geological Society of America annual meeting in Portland, Oregon in October. We’ve submitted four abstracts for the meeting, I am co-convening a session, and I’ll be helping lead a pre-meeting field trip.

I’ll be an invited speaker in a session on “Hydrologic Characterization and Simulation of Neogene Volcanic Terranes (T27)” and here’s my abstract:

On a template set by basalt flows, hydrology and erosional topography coevolve in the Oregon Cascade Range

Anne Jefferson

Young basalt terrains offer an exceptional opportunity to understand landscape and hydrologic evolution over time, since the age of landscape construction can be determined by dating lava flows. I use a chronosequence of watersheds in the Oregon Cascade Range to examine how topography and hydrology change over time in basalt landscapes. Western slopes of the Oregon Cascade Range are formed from lava flows ranging from Holocene to Eocene in age, with watersheds of all ages have similar climate, vegetation and relief. Abundant precipitation (2.0 to 3.5 m/yr) falls on this landscape, and young basalts are highly permeable, so Holocene and late Pleistocene lavas host large groundwater systems. Groundwater flowpaths dictated by lava geometry transmit most recharge to large springs. Spring hydrographs have low peak flows and slow recessions during dry summers, and springs and groundwater-fed streams show little evidence of geomorphically effective incision. In the Cascades, drainage density increases linearly with time, accompanied by progressive hillslope steepening and valley incision. In watersheds >1 Ma, springs are absent and well-developed drainage networks fed by shallow subsurface flow produce flashy hydrographs with rapid summer recessions. A combination of mechanical, chemical, and biological processes acting within and on top of lava flows may reduce permeability over time, forcing flowpaths closer to the land surface. These shallow flowpaths produce flashy hydrographs with peakflows capable of sediment transport and landscape dissection. From these observations, I infer that the geomorphic evolution of basalt landscapes is dependent on their evolution from deep to shallow flowpaths.

People just keep publishing interesting stuff.

Fiorillo, F. 2009. Spring hydrographs as indicators of droughts in a karst environment. Journal of Hydrology 373: 290-301.

Rosenberry, D.O. and J. Pitlick. 2009. Effects of sediment transport and seepage direction on hydraulic properties at the sediment–water interface of hyporheic settings. Journal of Hydrology 373: 377-391.

Gresswell, R. et al. 2009. The design and application of an inexpensive pressure monitoring system for shallow water level measurement, tensiometry and piezometry. Journal of Hydrology 373: 416-425.

Fryar, A.E. 2009. Springs and the Origin of Bourbon [Historical Note], Ground Water, 47(4): 605-610.

Cardenas, M. Bayani. 2009. Stream-aquifer interactions and hyporheic exchange in gaining and losing sinuous streams Water Resour. Res., Vol. 45, No. 6, W06429

Selker, John; Ferre, Ty P. A. 2009. The ah ha moment of measurement: Introduction to the special section on Hydrologic Measurement Methods Water Resour. Res., Vol. 45, No. null, W00D00

Hodgkins, Glenn A. 2009. Streamflow changes in Alaska between the cool phase (1947-1976) and the warm phase (1977-2006) of the Pacific Decadal Oscillation: The influence of glaciers Water Resour. Res., Vol. 45, No. 6, W06502

Matott, L. Shawn; Babendreier, Justin E.; Purucker, S. Thomas Evaluating uncertainty in integrated environmental models: A review of concepts and tools Water Resour. Res., Vol. 45, No. 6, W06421

Orr, Cailin H.; Clark, Jeffery J.; Wilcock, Peter R.; Finlay, Jacques C.; Doyle, Martin W. Comparison of morphological and biological control of exchange with transient storage zones in a field-scale flume J. Geophys. Res., Vol. 114, No. G2, G02019

Katsuyama, Masanori; Kabeya, Naoki; Ohte, Nobuhito Elucidation of the relationship between geographic and time sources of stream water using a tracer approach in a headwater catchment Water Resour. Res., Vol. 45, No. 6, W06414

Phillips, J.D. 2009. Landscape evolution space and the relative importance of geomorphic processes and controls. Geomorphology, 109:79-85.

And last but not least:

Pretty much all of: Hydrological Processes, Special Issue: Hyporheic Hydrology: Interactions at the Groundwater-Surface Water Interface. Issue Edited by Stefan Krause, David M. Hannah, Jan H. Fleckenstein. Volume 23, Issue 15, 2009.

Most especially this article:
Boano, F., Revelli, R., and Ridolfi, L. 2009. Quantifying the impact of groundwater discharge on the surface-subsurface exchange, Hydrological Processes, 23(15): 2108-2116.