What Is a Mushroom Shaped Pluton?

A laccolith is a mushroom-shaped pluton with a round top and flat bottom resulting from a Magma intrusion into parallel rock layers close to Earth's surface.

What type of pluton is completely parallel to the rock layers into which it intrudes?

Unlike the sill shown in Figure 18-6, which is parallel to the rocks it intrudes, a dike is a pluton that cuts across preexisting rocks, as shown in Figure 18-7. Dikes often form when magma invades cracks in surrounding rock bodies.

Is a mushroom-shaped body of intrusive igneous rock?

A laccolith also is concordant with country rock, but it is distinguished from a sill by having a flat floor with a domed (mushroom-shaped) roof (see Figure 6).