The Boulder Batholith

Probably, most of us living near Helena, Montana don’t wholly appreciate some of the unique geology surrounding us.  Certainly the outcroppings of the Boulder Batholith south of Helena create some of the more extraordinary landscape features.

A batholith is a formation of igneous rock created by bodies of magma that have been pushed to the surface from deep inside the earth.  Batholiths often express themselves as mountains or broad fields of stone outcroppings.  The Elkhorn Mountains are a result of the Boulder Batholith.  The Boulder Batholith is named for the massive collections of granite boulders that often dominate the countryside, extending all the way to Butte.

The boulders of the batholith have, at this late geological date, been split by ice and earthquakes, blunted and smoothed by wind and running water, and amassed into all manner of precarious stacks.  Some of the boulder outcrops look like whimsical castles made from the balloon-like stones.

Over more recent decades, people have constructed homes in the batholith protrusions, often squaring homes amid giant boulder fields and natural rock gardens.  Today I am posting a photograph of a friend’s home constructed in the boulder outcrops.   The photo was captured with my twice-as-smarter-than-me phone.

--Mitchell Hegman