What Is Karst?
Karst is a distinctive topography in which the landscape is largely shaped by the dissolving action of water on carbonate bedrock (usually limestone, dolomite, or marble).
This geological process, occurring over many thousands of years, results in unusual surface and subsurface features ranging from sinkholes, vertical shafts, disappearing streams, and springs, to complex underground drainage systems and caves.
How Karst is Formed
The process of karst formation involves what is referred to as "the carbon dioxide cascade." As rain falls through the atmosphere, it picks up CO2 which dissolves in the droplets. Once the rain hits the ground, it percolates through the soil and picks up more CO2 to form a weak solution of carbonic acid: H2O+CO2=H2CO3. The infiltrating water naturally exploits any cracks or crevices in the rock. Over long periods, with a continuous supply of CO2 - enriched water, carbonate bedrock begins to dissolve. Openings in the bedrock increase in size and an underground drainage system begins to develop, allowing more water to pass, further accelerating the formation of karst. Eventually this leads to the development of subsurface caves.
Sculpturing in solution caves
Among the most significant of the solutional sculpturings are the small scooplike depressions known as scallops. Scallops are dish-shaped depressions formed by eddies in flowing water against cave walls, floors and ceilings. These indentations can range in length from less than an inch to several feet, but are most commonly found towards the smaller size dimensions.??Scallops can form both in caves and on the surface where flowing water is in contact with a soluble material. Local eddies in the water flow produce turbulent swirls in the water, which dissolve away the bedrock. They are asymmetrical in cross section, having a steep wall on the upstream side and a gentler slope on the downstream side.
The figure below is an illustration of how a scallop forms. Upstream is to the left in the diagram. At point 1 the water flow separates from the main current at the upstream edge of the scallop starting the formation of an eddy. Within the eddy at point 2 the water flow type changes from laminar to turbulent. Water swirls in an eddy at point 3, entirely within the scallop. Lastly, at point 4 the water flow exits the downstream (shallower) edge of the scallop to continue downstream.
Figure 1: Water flow directions during the formation of a scallop. Upstream is to the left in the diagram.
Scallop lengths are inversely proportional to the velocity of the water that formed them. The faster the water flow, the smaller the resulting scallops.
Directions
Scallop cave is found at the end of the East Memekay Mainline close to where it connects to the Grilse Creek System. You will need to turn right on E500. You will also need to be aware that this is an active logging road. Large trucks will be common during the week days and possibly on the weekends so be prepared to pull over. I was in here on a Saturday an saw no traffic at all, so weekends may be your best bet if you want to try to avoid the logging trucks. Unless you know these roads well, I recommend you return the way you came. The Grilse Creek connector can be tricky to find and is not in the best shape anymore.
Once you find the area, there is a good pullout across the road for parking. The trail to the entrance is just back from where you park across the road. At the trailhead coordinated you will notice footprints on the bank. Just over the bank is a small clear area with a tree in the center. The trail resumes straight across this clearing. You should be able to hear running water from here. Follow the trail toward the sound and you will find a sunken area where the creek runs out of one hole and into the cave entrance.
If you decide to explore the cave. Be prepared. The rock near the cave mouth is extremely slippery! The creek does run through the cave so good boots or at least an extra pair of shoes is a must. The trail to the exit is across the road just down from the trail to the entrance. It is a bit tricky to spot from the road, but should be easy to find from the cave exit.
To Log this cache:
1. Feel free to post a photo of the cave entrance. You can choose to be in the photo or not or show your GPS, that's up to you.
2. Find evidence of scalloping and post a photo. (no need to enter cave)
3. See if you can determine the direction of water flow by looking at the scalloping. Email me your rationale for your conclusion.
Bonus: If you decide to explore the cave, take a waypoint at both the entrance and the exit and email me the length of the cave.
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