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18 June 2016
Two virtual weathered-out dikes in a fjord in eastern Iceland
Two 3D models for you today, both produced by my student Marissa Dudek, using photo sets I gathered in Iceland: Photoscan model by Marissa Dudek (That one has paleomag holes drilled into it!) Photoscan model by Marissa Dudek (That one I’m particularly pleased with. Given the circumstances of image acquisition, this is a very good result!)
18 May 2016
Pillow basalt exposures in the Columbia River basalts
Pillow basalts form when mafic lava erupts underwater. Here are several examples from the Miocene Columbia River flood basalts, a large igneous province in eastern Washington state.
15 April 2016
Friday fold: Shiny pahoehoe
James Farrell is our newest Friday fold source. Today he shares a primary (not tectonic) fold – the fold is in the ropy texture of a pahoehoe flow: Those colors! What a gorgeous rock. Thanks for sharing, James! You, too, can share your folds here. Send me your images. I look forward to featuring them on the Friday fold!
2 April 2016
Five new GIGAmacro images
Here are a few new images I’ve been working on with my home-based Magnify2 imaging system from GIGAmacro. Strophomenid brachiopods from Mississippian Mauch Chunk Formation, West Virginia: Link Boninite from New Caledonia: Link Lepidodendron scale-tree bark from Poland: Link Potassium feldspar crystal, from a pegmatite: Link Catoctin Formation greenstone from a feeder dike east of Linden, Virginia: Link Enjoy exploring them for details.
29 March 2016
Four new GIGAmacro images
Here are a few new images I’ve been working on with my home-based Magnify2 imaging system from GIGAmacro. Archean basement complex gneiss from the Gallatin Range of Montana: Link (If this looks familiar, that’s because one of the samples I imaged with the Photoscan 3D modeling technique and published on Sketchfab the week before last.) Banded iron formation from Minnesota with ooids and stromatolites: Link Intrusion breccia: Link Blue Ridge …
27 March 2016
Another trio of 3D models
Here are three more of my Photoscan-generated, Sketchfab-hosted 3D models of rock samples: Mud cracks in Tonoloway Formation tidal flat carbonates, Corridor H, West Virginia: Diorite from the eastern Sierra Nevada of California: Vein cross-cutting foliated & lineated gneiss, Blue Ridge basement complex, Virginia:
17 March 2016
A GIGAmacro view of the front and back of an anorthosite cobble
Here are two views of a single anorthosite cobble, collected in the Adirondack Mountains of upstate New York: Raw, natural surface: Link Slabbed and polished surface: Link As you zoom in and explore these GIGAmacro images, see if you can find the delicate little “necklaces” (reaction rims) of garnet wrapping around the few isolated pyroxenes!
2 November 2015
Norman Bowen’s papers
I got a special treat the week before last – one of my students this semester works at the Geophysical Laboratory of the Carnegie Institution in Washington, DC. During our unit on igneous rocks, he was prompted by the “Bowen’s reaction series” discussion to let me know that Norman Bowen’s notebooks were still extant at the Carnegie. He invited me down to check them out, and I readily accepted. Here’s …
29 July 2015
Positively-weathering volcanic dike near Granby, Colorado
My friend Barbara am Ende sent along this lovely image of a dike in Colorado: Here’s the site. You can see the dike in Google Earth. Dikes are fractures, filled with molten rock, which then cools and solidifies, sealing the crack shut. In this case, once it got uplifted to Earth’s surface and exposed, the dike rock is tougher (more resistant to weathering) that the older rock it cut across. …
23 July 2015
Purcell Sill, layer-jumping
After reading the post last weekend about the discordant offshoot of the Purcell Sill, Rich Gashnig (post-doc at Georgia Tech) sent me a few photos he shot at Piegan Pass (at the head of a side-canyon adjacent to the one containing Grinnell Glacier). They show the Purcell Sill leaving one stratigraphic horizon and jumping to another, with the intermediate zone of Helena Formation limestone bending to accommodate the different positions: …
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.