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Apr072011

The scales of geoscience

Helicopter at Mount St Helens in 2007. Image: USGS.Geoscientists' brains are necessarily helicoptery. They can quickly climb and descend, hover or fly. This ability to zoom in and out, changing scale and range, develops with experience. Thinking and talking about scales, especially those outside your usual realm of thought, are good ways to develop your aptitude and intuition. Intuition especially is bound to the realms of your experience: millimetres to kilometres, seconds to decades. 

Being helicoptery is important because processes can manifest themselves in different ways at different scales. Currents, for example, can result in sorting and rounding of grains, but you can often only see this with a hand-lens (unless the grains are automobiles). The same environment might produce ripples at the centimetre scale, dunes at the decametre scale, channels at the kilometre scale, and an entire fluvial basin at another couple of orders of magnitude beyond that. In moments of true clarity, a geologist might think across 10 or 15 orders of magnitude in one thought, perhaps even more.

A couple of years ago, the brilliant web comic artist xkcd drew a couple of beautiful infographics depicting scale. Entitled height and depth (left), they showed the entire universe in a logarithmic scale space. More recently, a couple of amazing visualizations have offered different visions of the same theme: the wonderful Scale of the Universe, which looks at spatial scale, and the utterly magic ChronoZoom, which does a similar thing with geologic time. Wonderful.

These creations inspired me to try to map geological disciplines onto scale space. You can see how I did below. I do like the idea but I am not very keen on my execution. I think I will add a time dimension and have another go, but I thought I'd share it at this stage. I might even try drawing the next one freehand, but I ain't no Randall Munroe.

I'd be very happy to receive any feedback about improving this, or please post your own attempts!

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Reader Comments (4)

I might add a few things:
-macrostructure (folds, thrust belts, etc.) which can be on the mm to km scale
-microstructure can get down to lattice defects (TEM studies)
-I think that magma also has some smaller effects like flow-banding, polymerization of magma to affect viscosity

Nice way of thinking of things, though.

April 7, 2011 | Unregistered CommenterElli

@ Elli,
thanks for commenting. Macrostructure and microstructure processes might deserve a more visual distinction.
Thanks for pointing out that magmas influence smaller scales. Partial melts, eutectics, and the like are at smaller scales still. Glad you were able to think critically about this picture and we'll consider these updates. Maybe it means more rows!

April 7, 2011 | Registered CommenterEvan Bianco

these are great exercises. when I taught the class that you will teach, I did a little exercise about scale with the students, only at 3 levels, just to get them to think about different scales of heterogeneity in reservoirs. As an example, I used one of the Halifax Formation outcrops along the 102 (nicely interbedded sandstones and slates, i.e. turbidites). It was for most of the students a stunning revelation, they had never been asked to think about the geologic record within the context of scales. I then did a lab on time scales (logarithmic) (which I'll tell you about some day) and that too they found very difficult to grasp. I find these these kind of exercises therefore very helpful, because they teach us how little everyone around us thinks about scales in time and/or space.

April 9, 2011 | Unregistered CommenterElisabeth Kosters

@Elisabeth: Thanks for taking the time to leave a comment. It will be fun to learn more about the exercise on the Halifax Fm. On reading your note, something occurred to me: when we look at the geological record, we're seeing an incompletely sampled representation of the natural world. I wonder how that filter looks in scale space... The filter itself is space and time dependent, and partly random. I need to think more about this angle. Cheers!

April 10, 2011 | Registered CommenterMatt Hall

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