Geology Hike

~Yesterday I went on a hike at Occoneechee Mountain State Natural Area, which is next to Hillsborough, North Carolina.  The hike was led by a volunteer geologist and was coordinated by the state park office. I’d never been to Occoneechee (pr: oh-ko-knee-chi) Mountain before – I’d never even heard of it – so this looked like an interesting opportunity.

^ On the left is our guide, Jean-Michel Margot, a retired Swiss geologist who also worked for IBM.  He now conducts these monthly walks on the mountain and has also helped produce a guidebook to the geology of the Eno River area.

^ Before Occonneechee Mountain became a state area, there were farms and homesteads on the mountain.  Now they lie in ruins; there’s little left of this house except the collapsed chimney.  Many of the trees on the lower parts of the mountain are comparatively younger than trees near the top, because the original trees were cut down for farmland.  The trail we hiked crossed what were originally roads between farms, but were now little more than collapsed, overgrown ditches.

^ Embedded quartz, with red iron oxide (rust).

Geologically speaking, Occoneechee Mountain is very interesting.  Travelling west from the North Carolina coast, it marks the very beginning of the Appalachian Mountains, which are some of the oldest mountains in the world.  The mountain consists almost entirely of quartz (SiO2), which is a very hard rock and so resists weathering – which is why the mountain is still here (albeit smaller than younger mountains such as the Rockies) after hundreds of millions of years of precipitation.

^ Yellow paint on tree trunks marks the boundaries of state parks in North Carolina.  Blue paint marks trails.  Triple rings mark the geographical corners of a state park.  These markings may come in handy if you get lost…however, Occoneechee Mountain is not very large and is also near a highway.  I was informed by M. Margot that there are no bears on the mountain, although I have my doubts.  I don’t think I could bear that.

^ Now, I know what you’re thinking.  “It’s just a rock.”  Just a rock?  JUST a rock?!  I’ll have you know that this is genuine Appalachian bedrock, that forms the interior of the mountain itself!  There are several ways to tell that it’s bedrock, but the most obvious is that it’s aligned to the southwest, which is the direction the Appalachian Mountains go.  Imagine the mountains being pushed up from underground hundreds of millions of years ago; the rocks that got pushed up against harder rock all ended up facing the same way.

^ Like any self-respecting geologist, M. Margot brought along a rock hammer.  To really “do” geology, you have to break open rocks and see what’s inside, because it’s often hard to tell what a rock is from the outside due to lichens, discolorations caused by weathering, oxidation, and so forth.  He let one of the hikers break open a couple of rocks.  One of the rocks was brittle shale and broke easily, but the quartz bedrock in the above picture was much harder to break.

^ There’s more to the mountain than rocks and trees; the area is also a biological sanctuary for a variety of plant and animal life.  The above picture is a laurel; in the summer, the area is also filled with blue- and blackberry plants.  The mountain is also home to large numbers of Brown Elfin butterflies (Callophrys augustinus); the trail we walked on was the Brown Elfin Trail.

^ Some more bedrock.  Another way to tell that it’s bedrock is that it has distinctive splits, which again are aligned to the southwest.  The kids in our group had a good time climbing on them.  Yes, so did I.

^ The destination for the hike was an abandoned quarry along the north side of the mountain.  The quarry has been abandoned for many decades, and there’s a scenic overlook above it.  However, a rockslide several years ago resulted in it being closed off.  Fortunately, at some point in our hike we acquired a park ranger who gave us permission to proceed; park management is gradually re-opening the overlook for the general public.

^ The day was clear, and the view from the overlook was fantastic.  I stitched together the above panoramic picture; please click on it for a better view.

^ The quarry…Fred Flintstone would be right at home!  The soft mineral pyrophyllite was once mined here, which is quite rare (albeit not extremely valuable) and has many industrial applications.  Among other things, pyrophyllite was and is used in space shuttle nose cones, ceramics, gaskets, bricks, and in chemical manufacture.  It was also used as filler for North Carolina’s first east-west railroad.  This quarry is inactive, but there’s another still-active quarry just next to Occoneechee Mountain that’s the largest pyrophyllite quarry in the world.

^ Compare the two types of rocks in the above image.  On the right is quartz bedrock: grayish, rigid, split, and aligned southwest.  On the left is soft, reddish-brown pyrophyllite.

^ View of the Eno River from the overlook.

^ The cube-shaped brick building in the back (the one with battlements on the roof) was once the headquarters and commandant’s house of the Hillsborough Military Academy, which recruited and trained soldiers for the Confederate Army during the Civil War.  After the war, the Academy was intermittently used as a school and for storage, and the barracks were dismantled as part of a WPA project in the 1930s.  The headquarters was renovated in the 1960s and is now a private residence.

I enjoyed the hike very much, and I hope you enjoyed these pictures.  I’ll definitely be returning to Occoneechee Mountain in the near future to walk down some of the other trails, perhaps in the spring when the plants are in bloom and the animals are out.