University:
University of Edinburgh
Course:
EASC08030 | Geology and Landscapes
Academic year:

2022
Views:

44

Pages:

38
Author:

bratsj1xi4

Edinburgh: shaped by volcanoes Volcano anatomy Lava flows and ash layers Plug Intrusion Types of volcano Grey volcanoes with silica-rich magma that tends to have high viscosity and lots of gas; results in explosive eruptions and steep-sided stratovolcanoes. Typical rock: andesite. Montserrat, Eastern Caribbean Red volcanoes with silica-poor magma with low viscosity that flows easily and allows gas to escape. Usually forms lava flows and flat ‘shield’ volcanoes. Typical rock: basalt. Krafla, Iceland Plate tectonics controls volcano type Plate tectonics controls volcano type Edinburgh’s volcanoes: two episodes Carboniferous Period 360-300 million years ago Continental rift in Midland Valley of Scotland. Surface volcanic activity across the area and magma intrusions. Early Devonian Period 420-400 million years ago Subduction-related volcanic activity across Scotland, including granite formation and surface volcanoes at Glen Coe, Ben Nevis, Lorne, Ochil and Pentland Hills. Episode 1: subduction Map of the world 450 million years ago  Laurentia Baltica Avalonia   Landscape fashioned by geology series, published by SNH/BGS www.scotese.com The Caledonian Orogeny Continental collision 420 million years ago Episode 1: subduction Igneous rocks formed at the end of the Caledonian Orogeny 420 to 400 million years ago Including most of the granite in the Highlands, Shetland and southern Scotland And the volcanic rocks of the Ochil, Sidlaw and Pentland Hills Image from Con Gillen, Geology and Landscapes of Scotland (2nd edition), 2013, Dunedin Pentland Hills: varied volcanic rocks Pentland Rocks is one of 25 leaflets published by Lothian and Borders GeoConservation, and available as free downloads from the Edinburgh Geological Society website. Pentland Hills Contrasting lava flows Warklaw Hill basalt Torduff Hill trachyte Black Hill, Pentlands Modern example: Montserrat Growth of lava dome November 1995 March 1996 Devastating pyroclastic flows Blackford Hill Andesite on Blackford Hill Evidence of pyroclastic flows? Andesite Tuff (lithified volcanic ash) Edinburgh’s volcanoes: two episodes Carboniferous Period 360-300 million years ago Continental rift in Midland Valley of Scotland. Surface volcanic activity across the area and magma intrusions. Early Devonian Period 420-400 million years ago Subduction-related volcanic activity across Scotland, including granite formation and surface volcanoes at Glen Coe, Ben Nevis, Lorne, Ochil and Pentland Hills. World map 340 million years ago – the Carboniferous Period Britain near the Equator, drifting north, close to the southern edge of a large, stable continent. Episode 2: rifting Second episode of volcanic activity, 360-330 million years ago. In Edinburgh, this includes the basalt rock of Craiglockhart Hill, Arthur’s Seat and also magma intrusions to form sills. Craiglockhart Hill Salisbury Crags & Arthur’s Seat ## Castle Rock City centre volcanoes Arthur’s Seat volcano Holyrood Park rock types Tuff (volcanic ash) Basalt (lava flow) Agglomerate (crater fill) Dolerite (magma intrusion) Whinny Hill lava flows Agglomerate, central vent Modern example: Japan Oshima volcano, Japan Active basalt volcano close to Tokyo. Fissure eruption in crater area, 21 Nov 1986. During the evening more than 10,000 people were evacuated safely, with no injuries. 1km 1986 lava flows James Hutton, Edinburgh genius But the man of scientific observation, who looks into the chain of physical events connected with the present state of things, sees great changes that have been made, and foresees a different state that must follow in time, from the continued operation of that which actually is in nature. James Hutton, 1726-1797 Hutton on Salisbury Crags “We have a good example of this in the little mountain of Arthur's Seat, by this town of Edinburgh. This is a peaked hill of an irregular erupted mass … on the north side we find remarkable masses of whin-stone in that regular form among the strata, and lying parallel with them. The most conspicuous of these basaltic beds forms the summit of the hill which is called Salisbury Craig. Here the bed of whin-stone, more than 60 or 80 feet thick, rises to the west at an angle of about 40 degrees; it forms the precipicious summit which looks to the west; and this is an appearance which is distinguishable upon a hundred other occasions in the hills and mountains of this country. t.andl sU'li'faM now 'vfil'v'v. v'1 v-v -.-, 'ч 'v ' ;'!' Shaped by volcanoes Shaped by ice The Volcanoes that Shaped Edinburgh Devonian Period: silica-rich volcanoes Blackford, Braid & the Pentland Hills: 410 million years old Carboniferous Period: silica-poor volcanoes Arthur’s Seat, Castle Rock & Craiglockhart Hills 340 million years old Salisbury Crags & Corstorphine Hill 320 million years old

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