ROUS in the Fire Swamp!

The above Rock Of Unusual Structure (ROUS) was partially unveiled after a March 24 burn of the woods, quite close to the marshlands.  Rolled uphill, it acts as the base rock for a cairn where the trail divides before the woods coming from the parking lot.

The rock at the cairn’s base is called a Xenolith.  It has a migratory story as interesting as most birds at the conservancy.  It is made up of lava flow from the earth’s crust, ‘assembled’ in the Lake Superior area and ‘transported’ south, likely through the Wisconsin Glacial Episode over 10,000 years ago.
 
A Xenolith is created by a volcanic explosion of sorts…magma rises to the Earth’s surface through cracks/pipes between the Earth’s crust and mantle. As the molten material rises, it tears off bits and pieces from the magma pipe made up of basalt or finely grained mudstone, siltstone or shale.  These bits and pieces get coated in magma (think berries wrapped in a chocolate fondue).  As the magma cools, the 'fondue' burns its way through rocks and often burns out entirely.  Occasionally the ‘berries’ in this example survive in a diminutive state and remain embedded inside the new igneous rock layer.  That’s the black rock above.  Known as a Batholith, this lucky lady started miles below our surface and came down from the US/Canada border to be with you today.   Be nice to her.  She’s had a hard life.