The laccolith is the sheet type of intrusive rock that has been injected within or between the layers of the sedimentary rocks and the pressure of the magmas is higher enough that the magmas are forced upwards and are folded in a dome-like a mushroom structure.
This little structure can grow in about a few months when formed with a single magma injections as these features tend to form at very shallow depths.
The same way as sills, laccoliths form from a more
viscous magma which collects as lens-shaped mass that arches the overlying
structure upward. They can be recognized
because of the dome they form at the surface.
