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10 March 2017
Friday fold: Sheba Mine sample
When touring the geology of the Barberton Greenstone Belt last August, our group visited the Sheba Mine, a gold mine high in the hills. Their geologist kindly showed us around and allowed us to visit his history-laden office. I have no idea where this sample originated, but it was the only fold I saw in the place, nestled between sepia-toned photographs and old lanterns and rusty picks. I wonder what …
2 February 2017
Banded iron formation in Barberton Mountain Land
Banded iron formation is an “extinct rock” that can be found in ancient marine strata such as those found in the Barberton Greenstone Belt. Visit an outcrop on the Barberton GeoTrail and contemplate the bizarre anoxic world that Earth used to be.
25 January 2017
Y-shaped joints on a basalt flow, Lake Mývatn, Iceland
A basalt flow in Iceland shows both enticing pahoehoe and fractures with a Y-shaped intersection pattern. Comparisons to bread loaves and east Africa suggest a reason why.
11 January 2017
More Messengers from the Mantle
Since I showed off the 3D kimberlite intrusion breccias yesterday, I feel as if I owe you some other photos from that lovely exhibit at the IGC. I apologize for the poor quality of these photos – the gorgeous samples were behind glass and brightly lit, which made photography difficult. But the rocks are sooooooooo pretty, I think you’ll enjoy viewing them just the same. Let’s start with a gargantuan …
10 January 2017
Two kimberlite intrusion samples presented in 3D model format
While in Cape Town for the 35th meeting of the International Geological Congress in August/September, I was delighted at the “Messengers from the Mantle: Craton Roots and Diamonds” exhibit on kimberlites. It was a world-class collection of excellent specimens that traveled to the Congress from across the city at the University of Cape Town. I took some photos of two specimens to make 3D models from, and my student Marissa …
28 October 2016
Friday fold: “the eye of Sauron” at Sibubule
Have a look at this week’s Friday fold – but be aware that it will be looking back!
26 October 2016
Archean meteorite impact evidence from the Fig Tree Group in Barite Valley, Barberton Greenstone Belt, South Africa
What does the sedimentary record of a giant meteorite impact look like? Turns out it is full of tsunami breccia, fine ash, hail-like spherules, and a barium-rich ocean’s crystal precipitates. Join us in the Barberton Greenstone Belt of South Africa to learn more.
24 October 2016
GIGAmacro views of komatiite
Erik Klemetti posted today at Eruptions about komatiite, which is apropos, considering I just finished imaging some samples of that ultramafic volcanic rock. Have a look at three samples from Barberton Greenstone Belt here, each from the 3.27 Ga Weltevreden Formation: Link GigaPan by Callan Bentley Link GigaPan by Callan Bentley Link GigaPan by Callan Bentley And, while we’re at it, here’s one from the Red Lake Greenstone Belt (~3.0 …
21 October 2016
Friday fold: a miniature ramp and flat
Sometimes you find big ideas in small places. Here, a South African chert boulder mimics in miniature fold and thrust belts the world over.
20 September 2016
A virtual field trip to examine the Peninsula Sandstone on Table Mountain
Take a virtual field trip to Table Mountain, near Cape Town, South Africa. Digital media to explore from the site include: a 3D model, 3 GigaPans, and a 360° spherical photo!
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.