Old Cumbria Gazetteer - geological walk, Sadgill to Gatescarth


included in:-	track, Sadgill to Gatescarth
	geological walk, Sadgill to Gatescarth
	Longsleddale volcanic rocks
civil parish:-	Longsleddale (formerly Westmorland)
county:-	Cumbria
locality type:-	geological walk
locality type:-	volcanic rocks
10Km square:-	NY40

MN photo:-	Information courtesy of Tim Pettigrew.

	BIZ28.jpg Ignimbrite, loose specimen from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004, Borrowdale Volcanics, Ordovician period. Ignimbrites are the results of a pyroclastic flow of volcanic ash, an explosive outpouring of gasses and fragents at temperatures of several thousand degrees Celsius which flow downhill at high speeds. As the semi-molten rock fragments begin to settle out they are drawn out by the flow, stretched into elongated shapes which can be seen in the surrounding matrix of finer ash. As the hot flow passes over wet sediments bubbles of steam make holes in the settling ash. The ash is compressed into a hard rock. The holes have been filled with feldspar crystals, leached out of the surrounding rock: Pettigrew, Tim (edited): 2004 BIZ29.jpg Turbidite or graywacke, loose specimen from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004, Silurian period. BIZ30.jpg Turbidite or graywacke, loose specimen from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004, Silurian period. BIZ31.jpg Andesite with amygdales, loose specimen from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004, Borrowdale Volcanics, Ordovician period. BIZ32.jpg Andesite with amygdales, loose specimen from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004, Borrowdale Volcanic Group, Ordovician period. BIZ33.jpg Andesite, loose specimen from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004, Borrowdale Volcanic Group, Ordovician period. BIZ34.jpg Andesite with amygdales and white feldspar crystals, loose specimen from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004, Borrowdale Volcanic Group, Ordovician period.

	Clues to the Volcanoes
	Walking up the track at the top of Longsleddale you are in an area of Borrowdale volcanic group rocks. The rocks you might see on the path provide clues to some of the volcanic activity.

MN photo:-	NB: beware my amateur geological knowledge.
	JandMN : 406 BXO49.jpg Rock, hand specimen of a igneous rock, ignimbrite, from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 2012. Ordovician? Borrowdale volcanic group. As the volcano erupted the lava fizzed at its mouth becoming more fluid, and the hot gassy 'pyroclastic flow' swept down from the vent. Molten lumps of lava in the ash were stretched out and flattened as the flow settled. The lighter lumps might be feldspar? (taken . .2012)

	JandMN : 407 BXO48.jpg Rock, hand specimen of a igneous rock, Andesite lava with vesicles, from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 2012. Ordovician? Borrowdale volcanic group. The vesicles are gas bubbles which came out of solution in the lava when pressure reduced as it erupted from the volcano (like bubbles in lemonade). (taken . .2012)

	JandMN : 408 BXO50.jpg Rock, hand specimen of a igneous rock, Andesite lava with amygdales, infilled vesicles, from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 2012. Ordovician; Borrowdale volcanic group. The vesicles are gas bubbles which came out of solution in the lava when pressure reduced as it erupted from the volcano. Later material permeated through the rock and desposited minerals in the holes, forming 'amygdales'. (taken . .2012)

	JandMN : 409 BXO51.jpg Rock, hand specimen of a slate metamorphosed from tuff, with spherulites, from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 2012. Ordovician; Borrowdale volcanic group. The slate probably came from Wrengill Quarry. (taken . .2012)

	JandMN : 405 BXO47.jpg Rock, hand specimen of a metamorhic coarse sandstone, turbidite or greywacke, from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 18 July 2004. Ordovician? Formed in an underwater avalanche or turbidity current. (taken 18.7.2004)

	JandMN : 410 BXO52.jpg Rock, hand specimen of a quartz vein in volcanic tuff, from the track from Sadgill to Gatescarth Pass, Longsleddale, Westmorland, 2012. Ordovician; Borrowdale volcanic group. The quartz is probably associated with faulting. (taken . .2012)

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