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 … Read more
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.
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.
Photo by Sarah O. Tune in tomorrow for the answer!
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.
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 … Read more
Callan’s answer to the riddle of the mystery outcrop is revealed. Spoiler: the glacier did it.
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.
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 … Read more
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.
A detailed description of one of the Virginia Blue Ridge’s most intriguing geologic formations: a maroon sedimentary sequence showing the advance of “Snowball Earth” glaciers in the Neoproterozoic.
Quite appropriately, Glacial Till won the new the latest edition of “Where on (Google) Earth?”, hosted here yesterday. The location I picked is the subject of a new paper by Mark Johnson and colleagues appears in the current issue of Geology (October 2010). It shows a place in Iceland where a piedmont-style outlet glacier called … Read more
Ice… serpentine… halite… What do they all have in common? I’ve discussed mineral “ghosts” here before — really, those are only pseudomorphs, where one mineral’s chemistry becomes unstable due to a change in conditions, and then a new mineral forms in the same space. I’ve also brought up the issue of clasts of minerals which … Read more
My friend Barry R., now residing in PostDocVille, Denmark, took a trip to Iceland last week to check out the eruption of Eyjafjallajökull. Unfortunately, by the time he got to the volcano, it was no longer spouting lava, but the scene is dramatic regardless. You can sample some of his photos below, or see the … Read more
Last Friday, I spent the evening riding up to New York on a bus. To pass the time, I had my iPod and a new paper by Francis Macdonald and colleagues in Science. The paper examines the timing of one of the episodes of “Snowball Earth” glaciation. There’s some important new data in this paper, … Read more