Andesitic_Peperite_from_Cumbria_in_England_-_Geograph_3470821.jpg (640 × 424 pixels, file size: 87 KB, MIME type: image/jpeg)
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Summary
| Description |
English: Andesitic Peperite. This was removed from Ghyll Scaur quarry. It shows the reaction between hot andesitic magma (900C?) and groundwater rich volcanic derived ash. The andesite has explosively fragmented as mini steam explosions ripped through the ash. There is no baked margin in peperites as steam is an excellent insulator.
The rock is part of the Borrowdale volcanic group. It represents Ordovician (450ma ish) rocks formed on an Avalonian island arc. The intermediate composition of the arc led to seriously violent ultra-Plinian explosions. The line of volcanoes preserves some of the most explosive eruptions known to man. Mapping of the Scafell caldera in the 1980s discovered more of these massive volcanoes. These eruptions would have blocked out the sun from most of the planet. Gas thrust of the rapidly degassing magma emplaced ash up into the stratosphere, with plumes reaching 50km. The ash matrix originated from pyroclastic density currents (PDCs) which sped down the volcano flank, possibly towards the end of the eruption with dome, caldera or plume collapse. (Battery at lower edge of rock, for scale.) |
| Date | |
| Source | https://www.geograph.org.uk/photo/3470821 |
| Author | Ashley Dace (https://www.geograph.org.uk/profile/29497) |
| Attribution (required by the license) | Ashley Dace / Andesitic Peperite / |
| Camera location |  | View this and other nearby images on: OpenStreetMap |  |
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Licensing
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This image was taken from the Geograph project collection. See this photograph's page on the Geograph website for the photographer's contact details. The copyright on this image is owned by Ashley Dace and is licensed for reuse under the Creative Commons Attribution-ShareAlike 2.0 license.
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| Annotations | This image is annotated: View the annotations at Commons |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 22:12, 9 May 2018 | | 640 × 424 (87 KB) | GeoWriter | User created page with UploadWizard |
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