The Pebble Spotter's Guide by Clive Mitchell

Author:Clive Mitchell [Mitchell, Clive]
Language: eng
Format: epub
Tags: science, Earth Sciences, Geology, nature, Fossils, Rocks & Minerals, Crafts & Hobbies, Holiday & Seasonal, Nature Crafts, Travel, Special Interest, General, Family, Adventure, reference
ISBN: 9781911657477
Google: rs8uEAAAQBAJ
Publisher: National Trust
Published: 2021-06-10T23:23:19.653969+00:00

Lapilli Tuff

This lapilli tuff is made of volcanic ash (‘tuff’) with dark grey to black teardrop-shaped fragments (‘lapilli’) of volcanic glass and rock.

Lapilli tuff is a crossover between an igneous and a sedimentary rock. The volcanic ash is deposited like a sandstone and may be termed a ‘volcaniclastic’ rock. The lapilli (Latin for ‘little stones’) were molten when they were erupted from the volcano. As they travelled through the air they became streamlined and cooled to form wispy strands of glass. Generally, the larger a piece is, the closer it fell to the volcano that expelled it; most fall within 20km (12 miles) of the eruption.

Lapilli tuff varies in colour: light to dark brown, grey to black, occasionally pinkish, yellowish or greenish. It has distinctive wispy fragments of darker volcanic glass.

Found: In a stream, Patterdale, Lake District, England

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