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Rockfish Gap is located at MP 105.5 on the Skyline Drive, and MP 0 on the Blue Ridge Parkway. It is located in the Blue Ridge Mountains between Charlottesville and Waynesboro Virginia, on Afton Mountain. The Appalachian Trail also passes through this gap.
A mountain pass (also gap, notch, col, or saddle) is a route through a range or over a ridge. When following the lowest possible route, a pass is locally the highest point on that route. Many of the world's mountain ranges have presented formidable barriers to travel and passes have been important since before recorded history, and have played a key role in trade, war, and migration.
Mountain gaps are commonly of two types:
WATER GAPS are usually an indication of a river that is older than the current topography.
The river likely established its course when the landform was at a low elevation, with a very low stream gradient and a thick layer of unconsolidated sediment. The river therefore established its channel without regard for the deeper layers of rock. A later period of uplift would then cause increased erosion along the riverbed, exposing the underlying rock layers. As the uplift of the earth continued, the river, provided it was large enough, would continue to erode the rising land, cutting through ridges as they formed, thus leaving a natural pass through the mountain or ridge.
WIND GAPS are a valley through which a waterway once flowed, but is now dry as a result, normally, of stream capture.
Stream capture is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed and flows instead down the bed of a neighboring stream. This can happen for several reasons, including:
• Tectonic earth movements
• Natural damming, such as by a landslide or ice sheet.
• Erosion
• Within an area of karst topography, streams may sink or flow underground and then reappear in a nearby stream valley. (The term karst describes a distinctive topography that indicates dissolution of underlying rocks by surface water or ground water. Water falling as rain or snow soaks into the soil and becomes weakly acidic as it reacts with carbon dioxide that occurs naturally in the atmosphere and soil, forming carbonic acid. The carbonic acid in the water serves to dissolve the limestone bedrock along the rock surfaces, eventually forming caves, caverns, sinkholes and aquifers.) The now-dry valley of the original stream is known as a wind gap.
Gaps or passes formed by these processes often provide practical routes for trails, roads, and railroads through mountainous terrain. Initially buffalo and Indian trails crossed the Blue Ridge at Rockfish Gap. In the 18th century, these trails were widened to accommodate the westward expansion of the Virginia colony. The Three Chopt road was established between Richmond and the Shenandoah Valley in the 1740’s. U.S. Route 250 was built through this gap in 1935, and in 1973 Interstate 64 was completed through the pass. The top of a pass is frequently the only flat ground in the area, and it provides a high vantage point, so it is often a preferred site for buildings. The flat area of Rockfish Gap was selected as the site for the Mountain Top Tavern. This tavern was the site of many important conferences, including a meeting in 1818 between President James Monroe, former presidents Thomas Jefferson and James Madison, and Chief Justice of the United States Supreme Court John Marshall along with 24 other dignitaries. Under Jefferson's leadership, they selected nearby Charlottesville over Staunton and Lexington as the site of the new University of Virginia.
To log this cache, please email the answers to the following questions:
1) Measure the altitude at Ground Zero
2) Looking east you can overlook Rockfish Gap. Notice the steep drop from the nearby ridge into the gap. Here you can see the U.S. 250 (Lowest road), Interstate 64 – built above U.S. 250 via an overpass, and Skyline Drive, which climbs up the high ridge to your left. This same road is the beginning of the Blue Ridge Parkway to your right. Look down into the gap and estimate the depth of the gap from Ground Zero
3) Due to the absence of water in the gap, it is clear that Rockfish Gap is a Wind Gap. Based on the above information, describe how you think Rockfish Gap formed and what happened to the original waterway.
4) Go to Waypoint 1 (N38 01.889, W 078 51.554)– this will take you to the actual gap. Measure the altitude at this point, and calculate the actual depth of the gap. Compare this number to the estimate you made in Step 2.
5) Post a picture in your log of yourself or your geocaching name overlooking the gap.
Please EMAIL the answers to these questions to the owner of this cache. Please do not post them in your log. If answers are not received within 24 hours of your log, your log will be deleted. Sorry about this, but too many caches trying to slide by without answers.
Congratulations to Team.Hepler for the FTF!
Additional Hints
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