Hyaloclastite
A hyaloclastite is a consolidated pyroclastic rock form that consists largely of fragments of volcanic glass .
composition
Hyaloclastite is a hydrated tuff - breccia , which is rich in black volcanic glass. This occurs in the form of flat, angular fragments with a size of one millimeter to a few centimeters.
Several minerals are found in hyaloclastic rocks. Sideromelan is an olive-green, obsidian-like, basaltic glass that was quickly quenched in water. It is transparent and pure; in contrast to the more common tachylite, the scattered iron oxide crystals are missing .
The glass fragments are usually surrounded by a yellow or brown layer of palagonite , which is formed when sideromelan reacts with water.
Emergence
Hyaloclastites arise when lava cools under water or ice cover and are therefore characteristic rocks in the area of subglacial or submarine volcanoes and of Tuyas . The fragmentation of the volcanic glass occurs by the force of a volcanic explosion or by thermal shock during rapid cooling.
literature
- R. Batiza, JDL White (2000): Submarine lavas and hyaloclastite , in: H. Sigurdsson, B. Houghton, SR McNutt, H. Rymer, J. Stix (Eds.), Encyclopedia of Volcanoes. Academic Press, San Diego, CA, pp. 361-381. ISBN 978-0126431407
- MT Gudmundsson, F. Sigmundsson, H. Björnsson (1997): Ice-volcano interaction of the 1996 Gjálp subglacial eruption, Vatnajökull, Iceland , in: Nature, 389: 954-957. doi : 10.1038 / 40122
- WH Mathews (1947): "Tuyas", flat-topped volcanoes in northern British Columbia , in: Am. J. Sci., 245 (9): 560-570. doi : 10.2475 / ajs.245.9.560
- JL Smellie, P. Skilling (1994): Products of subglacial volcanic eruptions under different ice thicknesses: two examples from Antarctica , in: Sedimentary Geology, 91 (1-4): 115-129. doi : 10.1016 / 0037-0738 (94) 90125-2
- JW Head, L. Wilson (2003): Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits , in: Journal of Volcanology and Geothermal Research, 121 (3-4): 155-193. doi : 10.1016 / S0377-0273 (02) 00425-0
Web links
- Hyaloclastite in the mineral atlas