geoscience

Earth and Environmental Sciences: More than just rocks.

The Department of Earth and Environmental Sciences at the University of Kentucky offers students a wide variety of potential job opportunities.

Earth and Environmental Sciences: More than just rocks. from College of Arts and Sciences on Vimeo.

PATH EXTINCTION & REINFORCEMENT

The development and change over time (evolution) of geomorphic, soil, hydrological, and ecosystems (Earth surface systems; ESS) is often, perhaps mostly, characterized by multiple potential developmental trajectories. That is, rather than an inevitable monotonic progression toward a single stable state or climax or mature form, often there exist multiple stable states or potentially unstable outcomes, and multiple possible developmental pathways. Until late in the 20th century, basic tenets of geosciences, ecology, and pedology emphasized single-path, single-outcome conceptual models such as classical vegetation succession; development of mature, climax, or zonal soils; or attainment of steady-state or some other form of stable equilibrium. As evidence accumulated of ESS evolution with, e.g., nonequilibrium dynamics, alternative stable states, divergent evolution, and path dependency, the "headline" was the existence of > 2 potential pathways, contesting and contrasting with the single-path frameworks. Now it is appropriate to address the question of why the number of actually observed pathways is relatively small.The purpose of this post is to explore why some developmental sequences are rare vs. common; why some are non-recurring (path extinction), and some are reinforced.

THE GEOMORPHOLOGICAL NICHE OF TREES

In a 2009 article I introduced the concept of a geomorphological niche, defined as the resources available to drive or support a particular geomorphic process (the concept has not caught on). The niche is defined in terms of a landscape evolution space (LES), given by

where H is height above a base level, rho is the density of the geological parent material, g is the gravity constant, and A is surface area. The k’s are factors representing the inputs of solar energy and precipitation, and Pgrepresents the geomorphically significant proportion of biological productivity (see this for the  background and justification).

BREAKAGE VS. UPROOTING & HILLSLOPE GEOMORPHOLOGY

Just published in Geomorphology:

Samonil, P., Danek, P., Adam, D., Phillips, J.D. 2017. Breakage or uprooting: how tree death affects hillslope processes in old-growth temperate forestsGeomorphology 299: 276-284. 

The abstract is below:

Posted 14 November 2017

 

HOW COMPLEX CAN IT BE?

Back in 2006, novelist and country music singer-songwriter Kinky Friedman ran (unsuccessfully) for governor of Texas. His campaign slogan, a rather pointed reference to the fact that recent occupants of the office George W. Bush and Rick Perry were not the sharpest tools in the shed, was "how hard could it be?" I can't answer that, but I can answer, after a fashion, the question of how complex or simple an Earth surface system can be.

AXIOMS OF GEOMORPHOLOGY

Axiomatic approaches to science and mathematics depend on an underlying set of statements, principles, or propositions that apply to all situations within the domain of study. The axioms run the gamut from undisputed universal laws to widely or even universally accepted but unproved or unprovable generalizations, to propositional stipulations adopted for analytical convenience or because they raise interesting questions.

Examples abound in mathematics and formal logic, and in science, engineering and technological applications of math and logic. Although it is only occasionally referred to as such, the laws of stratigraphy (details in any geology textbook) form an axiomatic approach to sedimentology, sedimentary geology, and related palaeoenvironmental studies. The laws of original horizontality, lateral continuity, superposition, and cross-cutting relationships are assumed in this approach to apply to all sedimentary deposits, and therefore form an axiomatic system for interpretation.

AMPLIFIERS & FILTERS

 

A big problem with predicting responses to global climate change (or other environmental changes) is that they are nonlinear and thus disproportionate. Sometimes large changes can have relatively small responses, while in other cases small changes can have disproportionately large impacts.

Responses to environmental change are sometimes characterized by amplifiers—phenomena that reinforce or exaggerate the effects of the change. For example, if coastal land is subsiding, this amplifies the effects of sea level rise. Or, when warming results in permafrost thawing, this releases methane, a heat-trapping greenhouse gas, this leads to further warming. However, there are also filters—phenomena that resist, offset, or diminish the effects of the change. For instance, if coastal land is tectonically or isostatically uplifting, this can offset or even eliminate effects of sea level rise with respect to coastal submergence. Or, if warming results in increased cloud cover, which reflects more radiation, this counteracts the warming.

Geomiracles

 

Science fiction and popular science writer Arthur C. Clarke once wrote that "any sufficiently advanced technology is indistinguishable from magic." Riffing on that theme, I once gave a talk in which I proclaimed that "any sufficiently improbable event is distinguishable from the miraculous." Some definitions of "miracle" invoke the divine or supernatural, but I have in mind the definition (in this case from the Merriam-Webster dictionary) as: "an extremely outstanding or unusual event, thing, or accomplishment." The point of the argument is that, due to the inescapable, irreducible role of geographical and historical contingency in Earth surface systems, all such systems (landscapes, ecosystems, soils, etc.) are unique in some respects (a formal argument along these lines is presented in this article: Phillips, J.D.  2007.  The perfect landscape.  Geomorphology 84: 159-169.). Thus the probability of existence of any given state of any given system at a given point in time is infinitesimally low. This exceedingly low probability makes nearly any environment in some senses extremely outstanding and unusual, and thus a miracle.

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