Volcanic pipe

As Chimney ( also vent passage, volcanic vent, puncture tube Blasts Judge, diatreme, Neck or eruption vent ) is called in geology the more or less vertical ascent channel of volcanic products from the Earth's interior to an eruptive center at the surface or on the seabed.

Form

Depending on the shape and position of the vents are called volcanic crater, eruption column or lava. Well-known examples are the Tuffschlote the Swabian Alb and the necks in Scotland, including Bass Rock.

Formation

On the origin of chimneys, it usually comes from explosive eruptions of very gas-rich magmas or by pure gas eruptions from great depths, which are often tied to tectonic zones of weakness, such as faults or fractures, but sometimes also through evaporation of groundwater. Due to the pressure relief at a rapid ascent of the magma it comes to such a sudden increase in volume and degassing of carbon dioxide and water vapor, that the promotion of rock debris can reach supersonic speeds. The process is somewhat similar to the opening of a warm bottle of champagne that have been previously shaken efficient.

Vent filling

The rocks which solidify or sediment (usually only little lava, volcanic breccia mostly ) in the vent, the vent form filling, also called Schlotpropfen. Due to the explosive eruption process numerous country rock fragments are often of the chimney walls pulled along ( xenoliths ). This can sometimes account for a significant share of the vent filling.

Of economic interest are the deposits of diamond-bearing kimberlite pipes of lamproite and in South Africa. You are at least three times as deep as most other known vents and reach into the deep crust or even up into the upper mantle down where the diamonds are. Its root zones consist mostly of solidified magma. Towards the top, the proportion of breccia increases more and more.

Because of their broken, loose filling can volcanic vents also serve as easy ways up and deposition sites of mineralizing solutions (fluids) from the deep. Many of the known deposits of copper and other metals are bound to such structures.

In the broadest sense, but also any cone-shaped body of rock debris can be called a chimney, whether it is of volcanic origin or not. In the caving vertical stretching a cave are called vent occasionally. In contrast to the well, the vents have evolved from bottom to top.