File:Basalt ventifact (Dry Valleys, Antarctica) 1 (31579270514).jpg
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Summary
[edit]DescriptionBasalt ventifact (Dry Valleys, Antarctica) 1 (31579270514).jpg |
Dolerite ventifact from Antarctica. (public display, Nebraska State Museum of Natural History, Lincoln, Nebraska, USA) Ventifacts are lustrous, polished rocks with subplanar to curved facets. They form by natural abrasion and polish by winds that carry sand grains. Ventifacts are naturally sand-blasted rocks. The rock itself is dolerite, also known as diabase. It is the shallow intrusive equivalent of basalt. Specimen-wise, it is essentially identical to basalt - a mafic, aphanitic igneous rock composed of plagioclase feldspar and pyroxene. From museum signage: "Rocks exposed to very long periods of wind action and dust storms show "carved" shapes ("ventifacts") produced by wind erosion. Professor San Treves of the University of Nebraska at Lincoln collected this ventifact. Some basalt rocks photographed by the Mars rovers may be ventifacts." Geologic unit: unrecorded/undisclosed, but almost certainly derived from the Ferrar Dolerite, Jurassic Locality: Dry Valleys, western side of McMurdo Sound, Antarctica |
Date | |
Source | Dolerite ventifact (Dry Valleys, Antarctica) 1 |
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@N05/31579270514. It was reviewed on 10 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
10 October 2019
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 00:22, 10 October 2019 | 1,756 × 1,678 (2.39 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/5 |
Date and time of data generation | 11:50, 17 July 2011 |
Lens focal length | 65 mm |
Orientation | Normal |
Horizontal resolution | 300 dpi |
Vertical resolution | 300 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 09:52, 20 January 2017 |
Y and C positioning | Co-sited |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 11:50, 17 July 2011 |
Meaning of each component |
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Image compression mode | 4 |
APEX exposure bias | 0 |
Maximum land aperture | 4.6 APEX (f/4.92) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash fired, strobe return light detected, auto mode |
DateTime subseconds | 70 |
DateTimeOriginal subseconds | 70 |
DateTimeDigitized subseconds | 70 |
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Color space | sRGB |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Scene type | A directly photographed image |
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Supported Flashpix version | 1 |
Image width | 1,756 px |
Image height | 1,678 px |
Date metadata was last modified | 04:52, 20 January 2017 |