You are browsing the archive for glaciers Archives - Page 3 of 4 - Mountain Beltway.
19 June 2013
Dwyka Tillite in South Africa
My wonderfully named e-buddy Martin Bentley recently took a field trip to a quarry in South Africa (between Grahamstown and Fort Beaufort) where the Dwyka Formation is exposed: This poorly sorted sedimentary rock (a ‘diamictite’) is usually interpreted as glacial deposits (lithified till, or ’tillite’). Alfred Wegener cited these rocks and accompanying glacial striations (and similar ones in South Africa, India, Australia, and Antarctica) as evidence for the existence of …
18 January 2013
Friday fold: “Chasing Ice”
Callan watches the new documentary “Chasing Ice” about James Balog’s Extreme Ice Survey project, and spots a lovely Z-fold during the largest glacial calving event ever recorded.
21 August 2012
Glacial striations, in fact and fun
A few photos from the Canadian Rockies illustrated the characteristic “look” of glacial striations. Callan also demonstrates how they can be used for outright tomfoolery.
6 August 2012
What are these geologists looking at?
Photo by Sarah O. Tune in tomorrow for the answer!
26 July 2012
Athabasca Glacier panorama
Click through for a big version… That’s the Athabasca Glacier, crown jewel of the Icefields Parkway in Jasper National Park, Alberta, Canada. Its lateral moraines show well its retreat and “deflation” in recent years.
30 March 2012
Friday fold: ice in Iceland
Searching for Peter Luffi’s latest Where On Google Earth? challenge, I found myself touring Iceland last week. While I didn’t find the strange comet-shaped feature he posted, I did find this: And zooming in a bit, to the high-contrast area in the center: This appears to be volcanic ash layers distorted by glacial flow and then melting/sublimation/weathering/erosion/ablation of the glacier. I posted something similar as the Friday fold almost a …
19 August 2011
Glaciofluvial outcrop annotated
Callan’s answer to the riddle of the mystery outcrop is revealed. Spoiler: the glacier did it.
15 April 2011
Friday fold: A cold one
The Friday fold is glimpsed from Google Earth. Atop a valley glacier in south-central Alaska’s Kenai mountain range, a fold of “transverse moraine” displays parasitic folds.
29 March 2011
Tillite in outwash
Hoo boy. This one made me yelp… While on the glacial geology of western Pennsylvania trip last Saturday, we visited a gravel quarrying operation. The operators were extracting gravel from a glacial lake delta deposit, and it was full of glacial outwash — sediments washed out from the melting front of the Erie lobe of the Laurentide ice sheet. We were there to look at the Pleistocene features, but several …
22 March 2011
Glacial cobble
Saw this beauty on a field trip Saturday, examining the glacial geology of western Pennsylvania. Note the faceted surfaces and profusion of scratches of multiple sizes in multiple orientations.
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.