These mostly forest-covered mountains hold a unique geologic structure, the Boulder Batholith. A batholith is a large mass of ...

But when you strike one of the rocks with a hammer, it emits an unexpected, resonant peal. The geological abnormality is part of the Boulder Batholith, a 1.2 million-acre mass of igneous rock ...

The granite intrudes Archean and Lower-Middle Huronian rocks and is overlain unconformably by Upper Huronian sediments. The Duluth gabbro cut across and metamorphosed its southeastern edge. In general ...

A batholith is a large mass of intrusive igneous rock that made its way to the surface. While relatively small by world standards, the Boulder Batholith, and by extension the Boulder Mountains ...