Weathering at Hinkle's Fort EarthCache

 
This granite historical marker recounts some of the first settlers to inhabit the area, and is the focus of this EarthCache!

What is Weathering?

Over time, even the hardest rock yields to the forces of nature. The process by which rocks break down and decay is known as weathering, and it plays a critical role in shaping Earth's surface. Unlike erosion, which involves the movement of rock particles, weathering occurs in place, gradually altering stone through physical forces, chemical reactions, and biological activity.

There are three primary types of weathering: physical (mechanical), chemical, and biological. Often, these processes act together, weakening and reshaping rock formations over thousands—or even millions—of years.
 

Physical (Mechanical) Weathering:

Physical weathering, also known as mechanical weathering, is the process by which rocks break into smaller pieces without any change to their chemical composition. It typically occurs due to temperature changes, pressure release, or mechanical forces like water, wind, or ice. One of the most common examples of this type of weathering is freeze-thaw action, where water seeps into cracks in rock during warmer weather, then freezes as temperatures drop. Since ice expands when it freezes, it exerts pressure on the rock, widening the crack. Repeated cycles can eventually split the rock entirely.

Another form of mechanical weathering comes from thermal expansion and contraction, especially in environments with large temperature swings, such as deserts or exposed mountain faces. As the surface of the rock heats during the day and cools at night, it expands and contracts, which causes outer layers to loosen and eventually peel away in a process called exfoliation. In addition, physical abrasion from wind carrying sand, glaciers dragging embedded rock fragments, or fast-flowing rivers tumbling stones can physically grind down surfaces. The results are often visible as jagged fragments, sharp edges, or even rounded pebbles smoothed by water.
 

Chemical Weathering:

Chemical weathering involves the alteration of the internal chemical structure of minerals in rock, changing them into new, usually softer and less stable substances. This process is especially effective in warm, humid environments where water is abundant. One of the primary mechanisms is hydrolysis, in which minerals like feldspar (common in granite) react with water to form clay. Over time, this reaction weakens the rock and can create soft, chalky surfaces or residual clay deposits.

Another common chemical process is oxidation, in which minerals containing iron react with oxygen in the air or water to form rust-like compounds. This often gives the rock a reddish or yellow-brown stain and makes it more brittle. You may notice this type of weathering on rocks with a rusty surface or crumbly, oxidized edges. Carbonation is also widespread, particularly in regions with limestone or marble bedrock. Slightly acidic rainwater (due to dissolved carbon dioxide) reacts with calcium carbonate in these rocks, gradually dissolving the stone and leaving behind pitted surfaces, rounded cavities, or even small sinkholes.
 

Biological Weathering:

Biological weathering is caused by the actions of living organisms, which can either physically break rocks apart or chemically alter them through metabolic processes. One of the most direct examples of this is root wedging, where the roots of trees or plants grow into small cracks in rocks in search of water or stability. As the roots expand, they exert pressure on the rock, widening cracks and eventually causing pieces to break off. You’ll often see this at rocky outcrops where trees cling to cliff faces or sidewalks where weeds break through pavement.

In addition to mechanical effects, biological organisms also contribute to chemical weathering. Lichens and mosses, for example, often colonize rock surfaces and secrete weak acids that slowly dissolve the minerals they cling to. Over time, this can soften the rock surface beneath them, leading to uneven pitting or discoloration. Even microscopic organisms in soil can produce organic acids that leach into bedrock and contribute to its slow breakdown. In some cases, animal activity—like burrowing or digging—can expose fresh rock surfaces to the air and moisture, accelerating other weathering processes.

About Hinkle's Fort
Fort Henckel, aka Hinkle’s Fort, was located deep in the Allegheny Mountains in West Augusta, western Virginia, when it was built in 1761-62 by Johann Justus Henckel (Hinkle), Sr. (706-1778), other members of his family with perhaps help from neighboring settlers. The location near Riverton, Pendleton County, West Virginia, in what is known as Germany Valley.

The fort was built as a protection for Henckel, his family, and other pioneers against the Native Americans who frequented the valley from time to time.

The fort may have been the only outpost in Pendleton County for the patriot forces during the American Revolutionary War. While it has been generally that recognized that John Justus Henckel, Sr. served as commander of the fort and furnished supplies to the troops of the Virginia Militia who were quartered there, solid primary proof of his service and that of the Virginia Militia who were head quartered there including the North Fork Military Company which had been organized by settlers early in the Revolutionary War.