Integrative Natural History of Minnesota's North Shore, Part 13: I'm Still in the Groove

Integrative Natural History of Minnesota's North Shore, Part 13: I'm Still in the Groove | Duluth

Yes indeed, we're still on the glacially abraded outcrop of North Shore Volcanic Group basalt on the Lake Superior coast at Kitchi Gammi Park. And for good reason. It's subject matter worth embellishing. This is one of the best places to see, study, and obsessively photograph a superb collection of glacial abrasion features.

The pen provides scale.

So far as I know, there are two really effective ways of polishing the kinds of stone that really will take a high-gloss shine.

One is to quarry it, cut it to desired size and shape, and then send it to a processing facility where skilled workers, using abrasives (diamond-surfaced pads, steel shot, or a slurry of emery grit and water) turn rough rock faces into smooth, reflective, and well-sealed surfaces resistant to weathering.

The other method is even more labor- and time-intensive. No quarrying is necessary, but you do have to figure out a way to reverse the current spate of anthropogenic global warming and throw the whole process in the opposite direction.

If you manage to cool the Earth sufficiently and trigger its next glacial phase, and if you live at sufficient high latitude or altitude, you'll eventually have an ice sheet roll over your desired rock outcrop and do what the Pleistocene-epoch Superior Lobe did to the North Shore Volcanic Group basalt here.

In this photo, the sunshine reflecting off the smooth, sculpted, and streamlined surface highlights the natural glacial polish that was applied between 15 and 10 ky ago. Also present is a striking set of linear striations.

If you look closely, you'll also spot some crescentic gouges, which also indicate the direction of glacial advance. The origin of both these features and the striations is treated in Part 11 of this set.

To see the other photos and descriptions of this series, visit
my Integrative Natural History of Minnesota's North Shore album.

Taken in: United States / Minnesota / Duluth / Lester Park (show map)

Taken on: June 20, 2008

Tags:

nature

geology

rocks

parks

stone

Kitchi Gammi Park

Duluth

Minnesota

North Shore Volcanic Group

basalt

glacial abrasion

striations

crescentic gouges

glacial polish

Midcontinent Rift « less

Sets appears in: • Integrative Natural History of Minnesota's North Shore • MCR: Homage to the Midcontinent Rift more » • Natural History: Minnesota • Rock Forms, Rock Formations « less

Camera: NIKON COOLPIX S4, 38mm, ISO 50 (more info) (hide info)

Camera:	NIKON COOLPIX S4
Focal Length:	38mm
ISO:	50
Flash:	Off, Did not fire
Exposure Program:	Program AE
Metering Mode:	Multi-segment
White Balance:	Auto
Color Space:	Uncalibrated
Show full info

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