I.—A Remarkable Rock Stream in East Iceland
In his account of the volcanoes of Iceland, Thoroddsen describes two types of acid lavas which have been extruded in post-Glacial, prehistoric times. First are the lavas of the Torfajökull district, of the usual nature of acid flows, building up a compact mass of bluish-grey rock with an outer casin...
| Published in: | Geological Magazine |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Cambridge University Press (CUP)
1917
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1017/s0016756800140038 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756800140038 |
| Summary: | In his account of the volcanoes of Iceland, Thoroddsen describes two types of acid lavas which have been extruded in post-Glacial, prehistoric times. First are the lavas of the Torfajökull district, of the usual nature of acid flows, building up a compact mass of bluish-grey rock with an outer casing of obsidian and pumice. These lavas have been poured out in the post-Tertiary country, but the second type of stream is found most frequently in the older parts of the island, which otherwise have witnessed no volcanic eruptions since Tertiary times. This type of flow results from eruptions of a peculiar character in which “vast outflows of halfmelted and unmelted masses of liparite, poured out from cauldronshaped depressions, stretch down into the lowlands” (1, p. 503). The best example of these “Liparitische Bloekströme” occurs in the Lodmundarfjord district, E. Iceland, and is especially described by Thoroddsen (2, pp. 159–161). In this paper the contention is put forward that the Lodmundarfjord blockstream is not a lava-flow but an unusual type of glacial moraine. |
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