Textural analysis of tephra from a rhyodacitic eruption sequence, Thira (Santorini), Greece
The Minoan eruption sequence of 1390 B.C. produced a minimum volume of 13 km/sup 3/ of rhyodacitic tephra (dense rock equivalent). The eruptions evolved from magmatic to phreatomagmatic and back to a mix of both processes. Thin section and scanning electron micrograph analysis of the tephra sequence provide information about eruption processes that is critical to interpretation of the field data. The eruptions began at a vent located above sea level and produced a coarse-grained Plinian pumice deposit. All later phases of the eruption involved propagating vent(s) into an older flooded caldera and flooding of the sea into a collapsing Minoan caldera. Interaction of magma and water produced fine-grained tephra that consist mostly of slightly curved, nearly flat shards and small pumice pyroclasts. These were derived during fragmentation of a heterogeneous, vesicular magma containing large compound vesicles and smaller, elongate vesicles. The vesiculated magma was thoroughly comminuted during magma-water interactions. The last eruptive phase is interpreted as having involved both magmatic and phreatomagmatic processes. Hot pyroclastic flows from this phase contained a bimodal mixture of pumice pyroclasts and finely comminuted shards.
- Research Organization:
- Los Alamos National Lab., NM (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6248275
- Report Number(s):
- LA-UR-83-117; CONF-830409-2; ON: DE83006053
- Resource Relation:
- Conference: Workshop on characterization and quantification of surface features on clastic and pyroclastic particles, Tempe, AZ, USA, 19 Apr 1983
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GREECE
VOLCANOES
RHYOLITES
PETROLOGY
ERUPTION
GEOLOGIC DEPOSITS
ELECTRON MICROSCOPY
GLASS
ISLANDS
MAGMA
MEDITERRANEAN SEA
PUMICE
DEVELOPING COUNTRIES
EASTERN EUROPE
EUROPE
GEOLOGY
IGNEOUS ROCKS
MICROSCOPY
ROCKS
SEAS
SURFACE WATERS
VOLCANIC ROCKS
580202* - Geophysics- Volcanology- (1980-1989)