Volcanic bomb

A volcanic bomb (formerly outcast ) is a ballistic flung out during a volcanic eruption Pyroklast, with a diameter of more than 64 mm. He has rounded shapes; the external shape and the surface show signs that the Pyroklast was melted during the formation and transport. In the older literature, each applies to a ballistic trajectory ejected Pyroklast as a bomb. In the recent literature, however, angular pyroclasts this size class are referred to as volcanic blocks. Pyroclastic rocks that consist of more than 75 % of volcanic bombs are called volcanic agglomerates.

Characteristics

Volcanic bombs, by definition, more than 64 mm in diameter, but can reach several meters. Their shape is usually oval or spindle-shaped, as they rotate during the flight and the common cold in the air around its own axis. In particularly gas-rich and viscous ( siliceous, " sour " ) lava arise so-called bread crust bombs. The abruptly transported through the high flow velocity in the pressure and temperature conditions of the Earth's surface glutflüssige lava hospitable violently during the ballistic flight. Thus an increase in size to the already existing bubbles in the material, on the other hand created more new. The problems caused by the swelling stresses can occur at the result of the rapid cooling solidified already in flight surface cracks that give the lava boulders the appearance of a loaf of bread.

Due to their relatively high weight drop the bombs in the vicinity of the volcano to the ground and therefore align compared to other volcanic concomitants relatively little damage.

Occurrence

Volcanic bombs occur in almost all igneous volcanic eruptions. Example, about the Islands volcanic areas or the volcanic areas in Italy. On the Italian volcanic island of Vulcano at the top of the fossa, for example, copies of volcanic bombs can be found. It involves ejecta of the eruption phase from 1888 until 1890. However you caused by the viscous heating that have become fragments of older volcanics.

In Germany, for example, volcanic bombs are often found in the vicinity of the Laacher See eruption and other centers of the volcanic Eifel. A particularly large specimen of a volcanic bomb is in Strohn issued (see photo).