Some features that you may encounter at Medoc Mountain include:
eastern margin of the Piedmont creates a gentle arc that connects many
urban centers including Raleigh, NC, several other state capitals (Trenton,
Richmond, Columbia, and Montgomery) and the nation's capital. This alignment
of urban areas is no accident but the result of decisions made by those
colonizing the Americas. After the colonists had established Atlantic
coast seaports at the mouths of major rivers they sailed upriver to the
rivers' navigable limits and established commercial centers at which to
gather goods from what was then viewed as the continent's interior.
Steps of crystalline rocks of the Precambrian and Paleozoic age (400 to 600 million years ago) marked the rivers' navigable limits. Early boatmen referred to this zone at the rivers' navigable limits as the fall line because it was there that each Atlantic-bound river contained rapids or less commonly, waterfalls.
The fall line marks the boundary between the darker sandy loams of the Coastal Plain to reddish, clayey soils of the hillier Piedmont. The Coastal Plain-Piedmont boundary is feathered and not clearly distinguishable by visual means, even at places such as Roanoke Rapids, an eastern North Carolina named because of its location at the navigable limits of the Roanoke River on the fall line. Medoc Mountain State Park lies 18 miles southwest of Roanoke Rapids and is also located along the fall line.
Sandy soils formed across much of the Coastal Plain as a result of the Atlantic Ocean's advancing and retreating across it and the surf's pulverizing, and the sea's salt dissolving all but the most resistant materials, namely quartzite, the basis of sand.
As you traverse the fall line the best means of assessing whether you are in the Coastal Plain or in the Piedmont is to look at and feel the soil. Islands of Coastal Plain can be found deep within the Piedmont and vice versa.
In terms of human settlement, towns that grew up along the fall line had the benefit of hydroelectric power generation through watermills and turbines powered by falling water. Many of North Carolina's early mills and factories were situated along the fall line.
The Medoc Mountain area is important to geologists and physical geographers because it is the site of considerable quantities of molybdenite, a mineral that contains the metal molybdenum. Molybdenum is valued as an alloy because of its combined properties of low weight and high strength. Although the molybdenum deposits at Medoc Mountain are among the largest in the southeastern United States, they are small compared to deposits in the western United States and have never been mined. Molybdenite is of interest as well because it is often occurs alongside the mineral pyrite also known as "fools gold".
|Quartz Veins and Float|
Medoc Mountain is underlain by a granite mass composed of the minerals quartz, feldspar, and mica. Quartz veins are found in the 300 million year old granite and the surrounding metamorphic rocks. The granite originally forced its way into the surrounding metamorphic rocks from below as molten masses (magma). Hot liquids moved into fractures and zones of weakness in the granite and metamorphic rocks and cooled, whereby silica precipitated out and formed the veins.
Quartz is very resistant to weathering and chemical decay. When quartz is found in abundance on the surface it is referred to as a float and it generally indicates that quartz veins are just below the surface. If you hike along the summit trail, a three-mile loop that begins at the Medoc Mountain State Park office, you will see a quartz float as the trail winds down the slope to the creek.
Head along the summit trail at Medoc Mountain State Park to where it steeply slopes downward through the woods and you will observe blocks of fine grained rock that are dark in color scattered across the surface. The blocks of rock are diabase, a type of igneous rock. The diabase can be traced in a straight line that is a few feet wide. This characteristic indicates that the rock is sheet-like and part of a vertical igneous intrusion referred to as a diabase dike.
Diabase dikes are of interest because diabase contains a relatively large amount of magnetite, a magnetic mineral. Geologists and physical geographers measure a rocks magnetic intensity because this information can help them study rocks that cannot be seen on the Earth's surface and create magnetic intensity maps that are useful for mineral exploration and interpreting the structure of rocks.
view of a dike.