Basaltic tephra layers form a considerable part of the postglacial tephra deposits in Iceland. They can be related to the volcanic systems that produced them by characteristics based on major and minor element chemistry. Microprobe analysis
of volcanic glass shards have made it possible to relate even very thin (1-2 mm) basaltic tephra layers in distal areas outside the volcanic zones to their source.
Relations between tectonics and volcanism in the Roman province, Italy in Tephra studies.
Three regional tectonic phases can be distinguished during the past million years: 1. formation of a large graben, 2. sinking of segments of the volcano complex, 3. faulting, accompanied by phreatomagmatic volcanism. Each event was followed by small
éruptions explosives| phénomènes phréatomagmatiques et ravinement| caractères spéciaux des ignimbrites à faible rapport épaisseur-étendue. Corrélation entre la forme du volcan et l'intensité de ses éruptions, les volcans ayant des éruptions de forte
More than 200 tephra layers deposited in early Tertiary diatomite and clay in northern Denmark record explosive volcanism in the Skagerrak and in the North Sea. The early activity is basaltic, rhyolitic, and mafic and salic alkaline while later
in type, wich may indicate volcanism in a shallow sea environment.
of studying compositionally-zoned magma chambers. They are also important in volcanic hazard studies, where the past pattern of explosive activity is used as a guide to the probable future behaviour of a volcano.
Quaternary volcanism in the Mediterranean region was highly explosive, especially in the Roman-Campanian province, the Aeolian Islands and the Hellenic island arc. Pantelleria and Etna were less explosive. Tephra layers originating from all
Volcanic ash layers from three major Holocene eruptions are found throughout southern British Columbia and are useful stratigraphic markers. Here the AA. show that energy dispersive X-ray fluorescence analysis and alpha counting are useful
Nature du volcanisme. Utilisation de la téphrochronologie pour la datation des vestiges archéologiques paléolithiques et néolithiques et pour l'étude de la croissance des volcans. Variations climatiques et variations du niveau marin. Huit