Intrusion referred to in geology generally the penetration of flowable material into existing rock body (eg by salt domes or soft clays in the overlying layers).

However, in most cases, the term refers to the penetration of molten magma and also in a somewhat blurred manner on the body of rock formed in such a manner. The igneous rocks that crystallize during solidification of magmas are therefore also referred to as intrusive. Here, depending on the depth in relation to the land surface at the time of intrusion, plutonic rocks ( plutonic, see also Pluton ), which solidified at a relatively great depth of subvolcanic intrusions (among Lakkolithe ), which solidified at relatively shallow depth, distinguished.