File:Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; Rt. 169 roadcut just west of Ely, Minnesota, USA) 8.jpg
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Summary
editDescriptionMetamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; Rt. 169 roadcut just west of Ely, Minnesota, USA) 8.jpg |
English: Metamorphosed pillow basalt in the Precambrian of Minnesota, USA.
This is an exposure of the Ely Greenstone, a distinctive and famous unit in northeastern Minnesota. Greenstone is a metamorphic rock typically dominated by the minerals plagioclase feldspar and chlorite, plus often actinolite and epidote. Before metamorphism, greenstone was basalt or gabbro - both are mafic igneous rocks. The above rocks used to be basalt - it was part of an underwater lava flow. The bulbous structures seen in this outcrop are pillows, which are diagnostic of underwater basaltic lava flow eruptions. Pillow basalts can be observed forming underwater in today's oceans at basaltic volcanic sites such as Hawaii. Geologic unit & age: upper member of the Ely Greenstone, Neoarchean, ~2.722 Ga Locality: roadcut on the northern side of Rt. 169, 1.8 miles west of the Rt. 1-Rt. 169 intersection, just west of the town of Ely, northeastern St. Louis County, northeastern Minnesota, USA (47° 54' 01.33" North, 91° 52' 42.23" West) References on the Ely Greenstone: Jahn & Murthy (1975) - Rb-Sr ages of the Archean rocks from the Vermilion District, northeastern Minnesota. Geochimica et Cosmochimica Acta 39: 1679-1689. Jirsa et al. (2010) - Geologic map of Minnesota, Precambrian bedrock geology, description of map units. Minnesota Geological Survey State Map Series S-22. |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/21501275386/ |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/21501275386 (archive). It was reviewed on 10 March 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
10 March 2020
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current | 01:45, 10 March 2020 | 4,000 × 3,000 (4.12 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/21501275386/ with UploadWizard |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/160 sec (0.00625) |
F-number | f/11 |
ISO speed rating | 80 |
Date and time of data generation | 08:49, 10 June 2015 |
Lens focal length | 11.614 mm |
Image title | |
Width | 4,000 px |
Height | 3,000 px |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 21:58, 18 September 2015 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 08:49, 10 June 2015 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 7.3125 |
APEX aperture | 6.90625 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 4 APEX (f/4) |
Metering mode | Pattern |
Flash | Flash did not fire, compulsory flash suppression |
Supported Flashpix version | 1 |
Color space | sRGB |
Focal plane X resolution | 16,460.905349794 |
Focal plane Y resolution | 16,483.516483516 |
Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Landscape |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 15:58, 18 September 2015 |
Unique ID of original document | 72995524878E930B9C68C918AC6BC6D9 |