Open AccessPleistocene explosions and pyroclastic currents in west‐central Anatolia
Author(s) -
NEMEC WOJCIECH,
KAZANCI NIZAMETTIN,
MITCHELL JOHN G.
Publication year - 1998
Publication title -
boreas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 74
eISSN - 1502-3885
pISSN - 0300-9483
DOI - 10.1111/j.1502-3885.1998.tb01424.x
Subject(s) - pyroclastic rock , tephra , geology , pyroclastic fall , volcanism , explosive eruption , volcano , current (fluid) , pleistocene , geomorphology , petrology , paleontology , tectonics , oceanography
The discovery of unexpectedly young tephra, with K‐Ar dates of 1.50 ± 0.18 and 1.38 ± 0.13 Ma BP, in the Lake Eǧirdir area sheds new light on the time‐span and magnitude of explosive volcanism in west‐central Anatolia and on the physical behaviour of pyroclastic currents. The Gölcük maar near Isparta, widely thought to have ceased its activity in Pliocene time, was apparently still erupting with strong explosions in the Early Pleistocene. The Eǧirdir tephra, 34 km NE from the volcano, indicate deposition from powerful pyroclastic surges directed by the topography. The depositing currents were fully turbulent and carried unusually large lithic clasts, up to 2–3 cm in diameter, in suspension, which is incompatible with the existing physical model for pyroclastic currents. Based on the tephra characteristics, a conceptual model of the pyroclastic current's segmentation, or lateral dynamic partition, is suggested and used further to explain the current's specific response to an encountered topographic barrier. The widely held concept of a pyroclastic current's vertical separation, or sharp rheological decoupling, is thought to describe a common secondary phenomenon.