MT. MERAPI
One of the more recently active volcanoes is Mt.
Merapi in central Java Island, Indonesia (see pics).
Mt. Merapi has had frequent eruptions for at least the last 2000 years, with
relatively quiet intervals at ~600-700 years ago & at ~1100-1400 years ago
(see Gertisser & Keller, 2003). Between 20 and 30 eruption intervals
have been recorded in the 1800s and in the 1900s. From May to June 2006, Merapi
was observed to issue lava flows, ash columns, and ash flows.
Porphyritic basaltic andesite (10.6 cm across) - this juvenile lava is sample from
a 14 June 2006 block & ash flow (pyroclastic flow) from Mt. Merapi.
Historically, most of Merapi’s lavas are basaltic andesites that are highly
porphyritic (more than half the rock volume). Phenocrysts are commonly
plagioclase feldspar & pyroxene.
Locality:
pyroclastic flow deposit at ~1200 meters elevation in the hamlet of Bebeng,
village of Kaliadem, ~30 km from Yogyakarta, central Java, Indonesia (7º 34’
57” South, 110º 26’ 51” East).
Sample collected & generously donated by Grant
Kaye & Tom Wilson (University of Canterbury).
Basaltic andesite ash (field of view ~5.2 cm across) from a 14 June 2006
block & ash flow (pyroclastic flow) from Mt. Merapi.
Locality:
pyroclastic flow deposit at ~1200 meters elevation in the hamlet of Bebeng,
village of Kaliadem, ~30 km from Yogyakarta, central Java, Indonesia (7º 34’
57” South, 110º 26’ 51” East).
Sample collected & generously donated by Grant
Kaye & Tom Wilson (University of Canterbury).
Some info. from:
Gertisser & Keller (2003) - Temporal variations in
magma composition at Merapi Volcano (central Java, Indonesia): magmatic cycles
during the past 2000 years of explosive activity. Journal of
Volcanology and Geothermal Research 123: 1-23.