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Outcrops > Rocky Islands by Robin Rohrback-Schiavone

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About This Gigapan

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Taken by
Robin Rohrback-Schiavone Robin Rohrback-Schiavone
Explore score
1
Print Pricing
$8.00 to $798.00
Size
1.91 Gigapixels
Views
1151
Date added
Dec 21, 2012
Date taken
Dec 20, 2012
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Description

The Rocky Islands are exposures of Proterozoic-age metagraywacke of the Mather Gorge Formation.

Graywacke is a "dirty" sandstone deposited by turbidity currents in submarine fans (a.k.a. "abyssal fans"), which are essentially big piles of sediment in deep ocean basins. This is likely the original environment where the Billy Goat Trail's mud and graywacke deposits accumulated.

Turbidity currents are dense, sediment-laden flows which flow along the bottom of the ocean, starting from a source area adjacent to a land mass. As they slow down, they deposit their largest grains first, and their finest grains last, creating the graded beds characteristic of graywacke.

In addition graywacke metamorphosed and tilted in the Taconian orogeny, the Rocky Islands display evidence of ongoing geologic processes perpetrated by the Potomac River. "Bathtub rings" around the islands' lower reaches tell of the river's changing level in response to climatic factors such as drought and precipitation. When the river floods, it deposits logs, trash, and other debris higher up on the islands, and bends trees on the islands to point downstream. If the water level is right and you know where to look, you can watch potholes the river scouring out potholes.

This was taken on a side trail off the towpath about 100 meters upstream of the Section A trailhead.


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Stitcher Notes

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GigaPan Stitch version 2.1.0161 (Windows)
Panorama size: 1910 megapixels (108380 x 17632 pixels)
Input images: 217 (31 columns by 7 rows)
Field of view: 124.6 degrees wide by 20.3 degrees high (top=15.1, bottom=-5.2)
Settings:
Vignette correction off
Original image properties:
Camera make: Canon
Camera model: Canon PowerShot SX260 HS
Image size: 4000x3000 (12.0 megapixels)
Capture time: 2012-12-20 11:54:27 - 2012-12-20 12:09:28
Aperture: f/6.8
Exposure time: 0.001 - 0.008
ISO: 100 - 800
Focal length (35mm equiv.): 502.6 mm
Digital zoom: off
White balance: Automatic
Exposure mode: Automatic
Horizontal overlap: 10.4 to 22.0 percent
Vertical overlap: 12.6 to 25.1 percent
Computer stats: 3996.82 MB RAM, 2 CPUs
Total time 1:09:46 (19 seconds per picture)
Alignment: 19:47, Projection: 4:39, Blending: 45:20
(Preview finished in 29:53)

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