Volcanic agglomerate
In petrography, a volcanic agglomerate ( Latin agglomerare , 'to agglomerate , to pile up' ) is a pyroclastic sedimentary rock that consists of more than 75 percent volcanic bombs , i.e. the coarsest pyroclasts (components> 6.4 centimeters).
The volcanic agglomerate is defined by the components, the grain size and the modal inventory of the component size . More than 75 percent of it consists of volcanic bombs, the rest can also consist of lapilli or volcanic ash . However, volcanic agglomerates are also often characterized by the lack of a matrix made of fine-grained material, so that the rock has a high porosity . Volcanic bombs are over 6.4 centimeters in diameter and, unlike volcanic blocks , have rounded shapes, indicating that the material was still molten at the time of ejection. If the constituents are still predominantly molten when they hit the ground, welding slag will form .
literature
- Roger Walter Le Maitre: Igneous rocks: IUGS classification and glossary; recommendations of the International Union of Geological Sciences, Subcommission on the Systematics of Igneous Rocks. 2nd ed., 236 pp., New York, Cambridge University Press 2002 ISBN 0-521-66215-X
Individual evidence
- ^ Hans Murawski, Wilhelm Meyer: Geological dictionary . 11th edition. Elsevier / Spektrum, Heidelberg 2004, ISBN 3-8274-1445-8 , pp. 262 .