File:Bennett Peak (Navajo Volcanic Field, northwestern New Mexico, USA).jpg
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Summary
[edit]DescriptionBennett Peak (Navajo Volcanic Field, northwestern New Mexico, USA).jpg |
English: Bennett Peak volcanic neck in New Mexico, USA.
The Navajo Volcanic Field in the Four Corners area of the American southwest has about 80 old, eroded volcanic centers (volcanic necks/volcanic plugs/diatremes) of Oligocene to Miocene age. The most famous and visually distinctive volcanic neck in the area is Ship Rock. Ship Rock and the dikes radiating from it are principally composed of the scarce igneous rock minette (= potassic mica lamprophyre, the intrusive equivalent of trachybasalt lava) and volcanic breccias. Typical Ship Rock minettes are dense, non-vesicular, finely crystalline, and are composed of alkali feldspar (K-Na feldspar), phlogopite mica (which glitters nicely in the light), diopside pyroxene, some olivine, plus other minor minerals. Published studies of the eruptive centers in the Navajo Volcanic Field indicate that the original volcanoes erupted violently. This typically happens if the magmas are rich in dissolved gases (water, carbon dioxide, sulfur dioxide, etc.). Minette magmas were not rich in dissolved gases. So why the violent eruptions? The magmas came in contact with groundwater, and the water boiled to steam while confined underground. The steam pressure increased until it overcame the strength of the overlying rocks, resulting in an explosion and the creation of a surface crater (maar). Volcanologists call these phreatomagmatic eruptions (a.k.a. hydrovolcanic eruptions). Locality: Bennett Peak, western side of Rt. 491/Rt. 666, near the town of Tocito, San Juan County, northwestern New Mexico, USA ------------ Mostly synthesized from: Semken, S. 2003. Black rocks protruding up: the Navajo Volcanic Field. New Mexico Geological Society Guidebook, 54th Field Conference, September 24-27, 2003: 133-138. (semken.asu.edu/pubs/semken03_nvf.pdf) |
Date | |
Source | https://www.flickr.com/photos/jsjgeology/29443608582/ |
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@N05/29443608582. It was reviewed on 29 November 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
29 November 2020
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current | 04:13, 29 November 2020 | 3,008 × 1,158 (2.99 MB) | Ron Clausen (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/jsjgeology/29443608582/ with UploadWizard |
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Camera manufacturer | NIKON CORPORATION |
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Camera model | NIKON D70s |
Exposure time | 1/800 sec (0.00125) |
F-number | f/13 |
Date and time of data generation | 14:02, 2 September 2007 |
Lens focal length | 44 mm |
Orientation | Normal |
Horizontal resolution | 300 dpi |
Vertical resolution | 300 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 23:10, 6 September 2016 |
Y and C positioning | Centered |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 14:02, 2 September 2007 |
Meaning of each component |
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APEX exposure bias | 0 |
Maximum land aperture | 4.2750070442378 APEX (f/4.4) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash did not fire, compulsory flash suppression |
DateTime subseconds | 70 |
DateTimeOriginal subseconds | 70 |
DateTimeDigitized subseconds | 70 |
Supported Flashpix version | 1 |
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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Focal length in 35 mm film | 66 mm |
Scene capture type | Landscape |
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Subject distance range | Unknown |
Image compression mode | 4 |
Supported Flashpix version | 1 |
Image width | 3,008 px |
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Date metadata was last modified | 19:10, 6 September 2016 |