On the way to the walk we were discussing the origins of Glassy Mountain and Kent researched it when he got home. Here is what he found.
Monadnocks are mostly about what’s there – not how they got there. A monadnock is an isolated hill of bedrock standing conspicuously above the general level of the surrounding area. Monadnocks are left as erosional remnants because of their more resistant rock composition; commonly they consist of quartzite or less jointed massive volcanic rocks.
Plutons are both about what’s there and how they got there – a pluton is a body of intrusive igneous rock (called a plutonic rock) that is crystallized from magma slowly cooling below the surface of the Earth.
The “lunch rock” where we sat today is clearly composed of volcanic rock – granitic gneiss – similar to what is found on Looking Glass Rock.
So, Glassy Mountain qualifies as a massive volcanic rock (aka Pluton) that now exists as an isolated hill of bedrock (aka monadnock) above the SC Piedmont. The distinction between Glassy Mountain and say, Table Rock or Looking Glass Rock, is that the area surrounding Glassy Mountain is relatively level compared to the mountains adjacent to Table Rock and Looking Glass Rock.
Bottom line: Glassy Mountain is a monadnock that is the remnant of a pluton.
Read more info on the plants at Glassy in Glassy Mountain Heritage Preserve by Patrick D. McMillan
Photography by Ken Borgfeldt, David Heavner, Penny Longhurst, & Jim Poling. Click on any picture to zoom.
Plants that are non-native to North America are indicated by an asterisk (*) placed after the species name.