Kolonneformer

Kolonneformer are a geological feature characterized by vertically oriented, polygonal columns that form when thick lava flows or intrusions cool and contract. The columns are typically vertical, extending downward from the cooling surface; cross-sections are usually hexagonal, but may be pentagonal or heptagonal.

Formation occurs as the outer part of a lava body cools rapidly and contracts, producing fractures that propagate inward. The regular spacing yields columnar joints that descend perpendicularly to the cooling surface. If cooling is rapid, columns are numerous and slender; slower cooling yields fewer, wider columns. Size and orientation can vary; individual columns can range from several centimeters to several meters in width, and from a few meters to several tens of meters in height.

Notable examples include Giant’s Causeway in Northern Ireland; Fingal’s Cave on the Island of Staffa; Svartifoss in Iceland; and Devil’s Postpile in California. In addition to basalt, columnar jointing can occur in other volcanic rocks such as andesite and rhyolite, though the columns are often less uniform.

The term Kolonneformer is used in Scandinavian languages to describe these features and is of interest in geology, volcanology, and geomorphology. Related phenomena include columnar basalts, polygonal weathering, and jointing in intrusive rocks.