Laccolith

A laccolith (Greek Lakkos λάκκος " Cistern ") is a bulging upward plutonic body with largely flat bottom in geology. It consists of magma that has solidified at shallow depth below the surface in the Earth's crust, and has at least one leading into the feed channel depth, which is often in columns ( Dyke ).

At emplacement the overlying rock was bulged, because the pressure of the overlying rocks was lower than the existing pressure in the melt, so that the bulge despite Lakkolithe are concordant to the surrounding rock. The rock is of acidic to intermediate composition.

The solidification depth lies between the igneous rocks at the surface (caused by volcanoes) and the igneous rocks at depth, the plutonic rocks. Phenomena of this kind belong to Subvulkanismus (also Tiefenvulkanismus and Kryptovulkanismus ).

A layer of bound and plate-shaped pluton without bulging of the overlying layers is called the sill. If it is a solidified lava in the vent of a volcano, it is called a vent or diatreme.