The islands form a circle and lie 10 kilometres (6 mi) southwest of North Bay.

Today the islands' sand beaches continue to be a popular resting and recreation spot for many boaters.

As the body of magma rises toward the surface, the volatile compounds transform to gaseous phase as pressure is reduced with decreasing depth.

This sudden expansion propels the magma upward at rapid speeds, resulting in a shallow supersonic eruption.

Minerals found associated with these rocks include: pyroxenites, amphibole, apatite, biotite, calcite, magnetite, monazite, nepheline, pyrite, pyrochlore, pyroxene and quartz.

It was established in 1989 and is representative of island ecology in Lake Nipissing with warmer than normal regional temperatures.