12 folds a-plunging

A post by Chris RowanOn the 12th day of Christmas my true love sent to me: 12 folds a-plunging…

Anyone with even a hint of structural geologist in their soul loves a good fold. As well as their geometrically appealing curves, they represent a tangible, easily read footprint of the tectonic forces that have lifted up the hills and mountains around you. A fold is said to plunge if its axis of curvature has been tilted away from the horizontal, such that the landscape will cut through the fold, rather than running parallel to it.

plunge.png

This means that when seen from above, plunging folds look rather beautiful; the differently eroding beds form a tableau of warped ridges and valleys, all co-operating to tell their tale of orogonies past.

Australia.jpg
Australia (click images to open in Google Earth)

Algeria.jpg
Algeria

Oman.jpg
Oman

IranFold.jpg
Iran

Cantabrians.jpg
Cantabrians

SouthAfrica.jpg
South Africa

Pakistan.jpg
Pakistan

Pakistan2.jpg
Pakistan again

Harrisburg.jpg
Pennsylvania

SplitMt_Utah.jpg
Utah

StGeorgeUT.jpg
Utah again

Wyoming.jpg
Wyoming

For the examples above (click here to open the full set in Google Earth) I’ve borrowed heavily from the SERC page of Google Earth mapping locations, as well as adding a few from my own personal experience. I was hoping to include at least one from the UK, but none of the examples I know of show up well on satellite; if you know of any, in Britain or elsewhere, I’d be happy to hear of them in the comments.

11 terranes amalgamating,

10 probes a-probing,

9 isotopes fractionating,

8 streams reversing,

7 glaciers melting,

6 fields a-flipping,

5 focal mechanisms,

4 index fossils,

3 Helmholtz coils,

2 concordant zircons,

and an APWP.

Thus ends my Christmas epic. Phew. I hope it provided some interest and enjoyment over the festive season.

Categories: geology, tectonics

Comments (8)

  1. I loved this series! And you saved the best (structure!) for last! Bravo, Chris – well done!

  2. Hypocentre says:

    On a small scale the beach at East Quantoxhead is good http://tinyurl.com/ydnjm75 or there are the Goyt and Roaches synclines in Staffordshire/Cheshire/Derbyshire http://tinyurl.com/y8eqb5p

  3. david says:

    An interesting well-done series. I enjoyed it very much, thanks.

  4. Great series, Chris. You’ve set a high bar for blogging here in 2010. :-)

  5. Alan Jacobs says:

    Like Prof Brian Greene ( “Fabric of the Cosmos”) you are an EXCELLENT teacher…..thank you.

  6. John Spraggs says:

    A local favourite of mine is the Sucia Islands, here in the Pacific Northwest. The forest hides the details seen in the desert images but the ocean reveals the topography nicely. A layman such as myself might speculate that glacial action removed the softer layers.
    http://maps.google.com/maps?&q=48.761944,-122.913333&spn=0.3,0.3&output=kml

  7. Matt M says:

    I enjoyed looking back at this series. As a resident of Houston, TX, I have no geology to look at except ditches in the clay. The most exciting rocks come from the local railroad, where they are starting to use pink granite as ballast.