earth and environmental sciences

Strat-and-Transition Models II

This is a continuation of my earlier post on applying state-and-transition models (STM) to stratigraphic information, to account for the missing bits.

Barrell’s (1917) explanation of how oscillatory variations in base level control the timing of deposition. Sedimentation can only occur when base level is actively rising. These short intervals are indicated by the black bars in the top diagram. The resulting stratigraphic column, shown at the left, is full of disconformities, but appears to be the result of continuous sedimentation. Noted sedimentologist Andrew Miall has used this example in several articles to illustrate the problems of gaps in sedimentary & stratigraphic records.

Strat-and-Transition Models


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

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

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:

UK's Yeager Part of Team That Finds Missing Deepwater Horizon Oil

Since the Deepwater Horizon disaster, also referred to as the BP oil spill, occurred in 2010, scientists have been searching for millions of gallons of unaccounted oil — 11 to 30 percent of the oil estimated to have been spilled — in the Gulf of Mexico.

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

Thursday, January 29, 2015 - 4:00pm
303 Sloane

Finding Faults: Inside Sean Bemis' Research

Sean Bemis put his hands together side by side to demonstrate two plates of the earth’s crust with a smooth boundary running between them. But that boundary is not always smooth and those plates do not always sit together neatly, which makes the earth’s crust a dynamic and complex surface.

On The Road Again

Sedimentary, My Dear Watson

Kevin Yeager's lab can measure the rate of coastline loss in Louisiana or document the effects of exposure to radioactive fallout.


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