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earth and environmental sciences

Strat-and-Transition Models

Submitted by jdp on Sun, 03/08/2015 - 06:46 pm

 

The reconstruction of past environmental change is more important than ever. First, we look for precedents, principles, and lessons from the past as we try to understand and predict ongoing and future environmental change based on the fundamental wisdom that “if it did happen, it can happen.” Second, all kinds of new ideas on the coevolution of life, landforms, climate, and Earth itself need testing, verification—and maybe most importantly—hypothesis generation from the historical record.

The most important historical records for all but the past couple of centuries are stratigraphic. Environmental change is recorded in the sedimentary rock record, in geologically modern sedimentary deposits, and in soil layers. However, geoscientists have long realized that the stratigraphic record is incomplete—“more gap than record,” Derek Ager famously pointed out, with the preserved events equally famously termed “frozen accidents.” The current state of affairs is well summarized in and recently published volume titled Strata and Time: Probing the Gaps in Our Understanding (Smith et al., 2015).

Graph Theory in Geosciences

Submitted by jdp on Fri, 02/27/2015 - 10:15 am

Wolfgang Scwhanghart, Tobias Heckmann and I have collaborated recently to review applications of graph theory in geomorphology and the geosciences in general. One of our papers, Graph Theory in the Geosciences, was just published in Earth-Science Reviews. The abstract is below. Our other joint paper, dealing specifically with graph theory applications in geomorphology, is still in press (in the journal Geomorphology) even though it was completed and accepted before the ESR paper. Go figure. 

Resources and Biodiversity

Submitted by jdp on Tue, 02/24/2015 - 03:16 pm

What is the relationship between the diversity of resources (e.g., space, sunlight, water, nutrients) and biodiversity? In most cases it is direct and positive—that is, the greater the diversity of resources the greater the biodiversity.  The relationship is also often mutually reinforcing—that is, byproducts, detritus, and the organisms themselves increase the diversity of the resource base. Of course, ultimately both resource and biodiversity are limited by both abiotic and biotic controls. The relationships look something like this:

Δ DELTAS

Submitted by jdp on Fri, 01/23/2015 - 01:44 pm

 

Several studies have noted the temporal coincidence between shoreline erosion around some major deltas (e.g., Nile, Mississippi, Ebro), and the reduction of stream sediment loads due to reforestation, soil conservation practices, and trapping of river sediment behind dams. There are, of course, excellent reasons to suspect a causal link, but the link itself has not, in my view, been fully established.

Rast-Holbrook Seminar

4:00-4:25 Dr. Adam Milewski, Assistant Professor of Geology, University of Georgia, "The Past, Present, and Future of Water Resources in the Middle East and North Africa Region"
4:30-4:55 Dr. Neda Zawahri, Associate Professor of Political Science, Cleveland State University, "Management of Transboundary Rivers in the Middle East"
5:00-5:25 Discussion moderated by Dr. Alan Fryar

Date:
Location:
303 Sloane

THE CYCLE OF EROSION

Submitted by jdp on Sun, 01/11/2015 - 01:43 pm

 

Out on the trails of Shaker Village at Pleasant Hill, Kentucky, this morning, I got to thinking about William Morris Davis’ “cycle of erosion” conceptual model (also called the geographical or geomorphological cycle). The drive-by, oversimplified version is that landscape evolution starts with uplift of a more-or-less planar, low relief surface. Weathering and erosion goes to work, and results in an initial stage of increasing relief as streams carve valleys, and slope processes operate on the slopes thereby created. Eventually, however, as the streams begin to approach base level, a new stage of decreasing relief begins as hilltops and drainage divides are lowered and valleys infilled. This continues until the entire landscape is about as close to baselevel as the geophysics of mass transport will allow, creating a low-relief, almost-planar surface called a peneplain. At some point a new episode of uplift occurs and the cycle begins anew.

I was thinking of this because many landscapes in the world, like the one I was viewing this morning, do give the impression of a dissected plateau or a low-relief surface into which denudational processes have cut.

HYDROPEDOLOGY: FLUX-STRUCTURE INTERACTIONS

Submitted by jdp on Mon, 12/29/2014 - 09:54 am

Subfields such as biogeomorphology, ecohydrology, geoecology, soil geomorphology are areas of overlap between disciplines and subdisciplines. They are governed by the paradigms of the overlapping fields, and fit more or less comfortably within, and at the boundaries of, those fields. They do not have an independent paradigm or conceptual framework (which in no way reduces their importance or vitality).

Landscape ecology, by contrast, has developed its own paradigm—pattern, process, scale—that is independent from mainstream ecology, biogeography, and geospatial analysis.

Does, or can, hydropedology have such an independent paradigm? Is its development best served by, say, the ecohydrology or soil geomorphology model as an overlap field dominated by existing paradigms of pedology and hydrology? Or is a landscape ecology, separate paradigm direction more appropriate?

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