How does a landscape go from looking like this…
~1500 year old basaltic lava landscape with no surface drainage
to looking like this?
2 Million year old landscape on basaltic lava. Note steep slopes and incised valleys
Find out in my new paper in Earth Surface Processes and Landforms.
Hint: Using a chronosequence of watersheds in the Oregon Cascades, we argue that the rates and processes of landscape evolution are driven by whether the water sinks into the lava flows and moves slowly toward springs with steady hydrographs or whether the water moves quickly through the shallow subsurface and creates streams with flashy hydrographs. Further, we suggest that this water routing is controlled by an elusive landscape-scale permeability which decreases over time as processes like chemical weathering create soil and clog up pores in the rock. And as a bonus, because of the high initial permeability of basaltic landscapes, the formation of stream networks and the dissection of the landscape appears to take far longer than in places with less permeable lithologies.
Jefferson, A., Grant, G., Lewis, S., & Lancaster, S. (2010). Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA Earth Surface Processes and Landforms, 35 (7), 803-816 DOI: 10.1002/esp.1976
You know, it’s kind of funny: this is basically what I’ve always intuitively assumed with respect to the evolution from a fresh lava flow to an incised landscape. But I’ve always been aware that it’s just my guess. It’s nice to see some actual research supporting the idea.
Is the first picture around Santiam Junction?
By: Lockwood on June 16, 2010
at 11:23 am
Looks like an interesting paper. Might be a touch out of my level. Would you say it’s accessible to a high standing 2nd year geology undergrad? How many pages is it?
By: Vadrosaul on June 18, 2010
at 5:48 pm
Lockwood: The first picture is north of Clear Lake just east of 126, just south of 20…so a few miles from Santiam Junction. The second picture is just a few miles west of the first one, north west of Smith River Reservoir. Both are in the McKenize River watershed.
Vadrosaul – I’d like to think that large parts of it are accessible to an undergraduate, though likely some techniques are unfamiliar to you. It’s 14 pages, with a bunch of figures and a pretty color map.
By: annejefferson on June 18, 2010
at 8:41 pm