Tuesday, August 10, 2010

Landscapes into Rock - geoscience meeting

This fall I will attend and present at the William Smith 2010 meeting "Landscapes into Rock", hosted by the Geological Society in London, 21-23 of September.  Landscape into Rock is an inspiring title, with an even more inspiring set of sessions and keynote speakers.  Below is a synopsis of the meeting; you can also go to the website here, find out more, and register if you are planning to attend.

The Erosional Engine - co-chaired by Alex Whittaker (Imperial College London) and Andy Carter (Birkbeck College, University of London);  Keynote speakers: Kelin Whipple (Arizona State University) and Niels Hovius (Cambridge University)

The Dynamics of Sediment Routing Systems - co-chaired by Alex Densmore (Durham University) and Ruth Robinson (St. Andrew’s University):Keynote speakers: James Syvitski (University of Colorado-Boulder) and Chris Paola (University of Minnesota)

Landscapes into Rock: the Making of Stratigraphy - co-chaired by Sébastien Castelltort (ETH-Zürich) and Emma Finch (Manchester University); Keynote speakers: Mike Leeder (University of East Anglia) William Smith Lecture 2010 and Rudy Slingerland (Pennsylvania State University)

Integrative Studies of Sediment Routing and the Petroleum System - co-chaired by Ian Lunt (Statoil) and Mike Blum (ExxonMobil); Keynote speakers: Ole J. Martinsen (Statoil) and Peter Burgess (Shell)

I am planning to microblog (via twitter and Tumblr) in real time, and blog at the end of each day (in semi-real time at Romania Rocks), but I do not promise.  Internet connection can be quite a luxury while abroad (especially in Europe) and I hate paying an arm and a leg for the real-time thing.  In any case, I will certainly take good notes and blog heavily real-time or after the event.
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Comparative geology

I am starting a new series of posts on “comparative geology”, in which I will compare and contrast geological features, settings, processes, events mostly for … the fun of it. Comparison is used as an investigative tool in other sciences; comparative anatomy is one example. The closest to my background is the case of sedimentary geologists using the term “analogs” when they compare rocks formed in similar depositional settings. Often analogs are used to compare rocks in the subsurface, where information is sparse and often one-dimensional (or three-dimensional but low resolution), with outcrops where rocks may be often seen in three-dimensions, touched, smelled, even tasted (ok, you have to be a geologist to enjoy that aspect). Another example of comparative geology is from the Earth and Planetary Sciences, where geomorphic or geologic features or processes on Earth are compared to those observed on other planets, with the goal of understanding processes on distant places in the Universe. The “distributary fans on Mars” are one example of this comparative geology concept.

The idea came to me this past week, while on vacation in the Sierra Nevada, a paradise for geologists. Many places I've seen during this trip reminded me one way or another of geologic features or settings in Romania; hence the opportunity for comparative geology on Romania Rocks.

There are many advantages for using comparison as an investigative tool in geosciences: when you compare and contrast features or processes, you understand them better; and then, there is the opportunity to come up with that wacky idea that would turn into a big breakthrough because you looked at things in a different way, or from a different perspective.
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Monday, August 9, 2010

Geology field notes: granite exfoliation

The "Geology field notes" is intended to be be a series of short posts on observations, measurements or geologic features I was intrigued by, awed or excited enough to take a picture of while in the field.

I returned recently from a trip to the Sierra Nevada and I was lucky to be able to spend some time in the Yosemite area.  What a paradise for geologists and outdoor enthusiasts alike!

Exfoliation features, or exfoliation joints, are commonly seen in Yosemite.  There is still debate about their genesis, but is it believed that they occur when concentric shells or plates of a rock break from its surface.  Exfoliation is common in intrusive igneous rocks such as granite, formed under great pressure and temperatures. When granitic rocks are exposed to the surface, the pressure is released and the granite expands slightly, resulting in exfoliation.

There are many examples of exfoliation feature in Yosemite; I will show here only a couple, the Royal Arches and the North Dome, both visible from the Glacier Point.
© RomaniaRocks

The Royal Arches (labeled RA in the figure above) formed during the Pleistocene glaciation, when glaciers peeled away the outer exfoliation shells along the side of an exfoliation dome, the North Dome (labeled ND in the picture above).  The smooth and broad arches were possible to form primarily because of the strong and homogenous fabric of the rock.  The more geologically inclined folks would be excited to know that the rock that made the arches possible is a coarse-grained granodiorite of Cretaceous age (87 my old),  with well-formed plates of biotite and long rods of black hornblende, an especially good rock to provide the geologist with exfoliation features.  Also in the picture above (and below) is the Washington Column (WaC), separated from the Royal Arches by a steep gully, which is a major joint in the granodiorite.
© RomaniaRocks

The outer arch of the Royal Arches spans a distance of ~550m (1800 feet), is about 60m (200 feet) thick and 300m (1000 feet) high.
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