When Clints and Grykes Become Trenches
This is an Earthcache. There is no container to be found. In order to long online, visitors must answer the questions in this description and send a message to the Cache Owner.
On their website, Ontario Conservation (ontarioconservationareas.ca) lists the following geologic highlights for Callaghan’s Rapids Conservation Area: “Limestone bedrock river, caves, sink holes, rapids” Likely they do not list “Clints” and “Grykes” as a geologic tourist attraction, because most visitors wouldn’t know what clints and grykes are. In this Earthcache, you are going to learn what they are.
On the west side of the Crowe River in the Callaghan’s Rapids Conservation Area, you can find an excellent example of highly developed clints and grykes that have been exposed to the perfect conditions for becoming deeper over time. These clint and gryke formations no longer appear to be a “pavement” with fissures, but appear like deep “trenches” that semi-fill with water in spring, (when the Crowe River floods), and then go dry in summer and fall. Here is an explanation of the geology of clints and grykes:
https://www.youtube.com/watch?v=poJ5wRHS-3E
35 second Youtube video (by Pres Currylea Geography Presentation College) that demonstrates the formation of clints and grikes (grykes).
Grykes are vertical or near-vertical fissures in limestone pavement. The retreating glaciers left the Canadian landscape scraped of topsoil, and in some cases, exposed flat beds of limestone or dolostone. Initially, limestone contains only microscopic fractures or cracks. Over time, rainwater seeps into the cracks and dissolves the limestone along the cracks, making them wider and deeper. Once it is large enough to be seen as a crack, it is called a grike, gryke, (or scailp).
Limestone is dissolved because rainwater is a weak carbonic acid. The joints which are widened and deepened by this chemical weathering are called grykes. The remaining blocks of limestone separating the grykes are called clints. The word, “karst” refers to all geologic phenomenae involved in the formation of caves and caverns. Karst includes deep clints and grykes, especially in the situation where the grykes form partially or fully underground.
Many flat alvar plains or fields have clints and grykes, but not karst features. In the geological situation of Callaghan’s Rapids, moving water is the factor that creates the karst landscaping. Depending on what time of year you visit, you may see water flowing in or out of the trenches (grykes). You may see water dripping from the tops of the clints. You may see plant life that is part of the equation in the chemical weathering of the grykes. And you will definitely hear the Crowe River as it flows over the rapids nearby. The Crowe River regularly floods into the grykes during spring run-off, causing erosion and an ever-deepening of the trench-like geography.
Grykes are important to the ecology of an area. Grykes can be a moisture reservoir and a habitat for some types of plants as well as homes and protection for animals against predators. Grykes can be channels that allow surface water to flow and become groundwater. Under very special conditions, such as those at Callaghan’s Rapids Conservation Area, grykes can become caves and provide homes for bats and other cave-dwelling creatures.
Questions:
-
-
From the parking to this Earthcache, is about a 600 metre walk along a trail that might be muddy in spring. Boots are recommended. Once at Ground Zero, if you can get into one of the trenches safely, measure your height against it. If the grykes are filled with water, stay on the top of a clint and estimate the depth (in feet) to the bottom of the gryke.
-
At the posted coordinates, there is a small cave. Is it possible to crawl through and come out on the other side of the cave? Can you find other small “caves” nearby (within 20 metres)?
-
Using geologic information given in the description, tell why you think these grykes resemble trenches and how they may have formed here. Talk about what you see in geologic terms such as shape and formation of the rock, presence or absence of water, size and dimensions of the "trenches" (grykes).
-
Take a picture of yourself or your GPS at the posted coordinates and upload the photo with your online log.
Word of caution: When walking on top of a karst landscape, you must be very cautious not to misstep into a crevasse and twist an ankle or worse. Some of the cracks might be covered by plants or snow. Keep alert, watch where you step, move slowly, and stay safe. The first 300 metres of the trail, from the parking, is wheelchair accessible in dry seasons, but the last 300 metres to Ground Zero is not wheelchair accessible.
Please note : The Crowe Valley Conservation also allows deer hunting in the first 2 weeks of November and posts signs closing the Conservation Area to visitors who are not hunting.
Directions: Follow Highway #7 east from Havelock or west from Marmora. Watch for Tiffen Road, which is the second concession road west of the town of Marmora. Turn south on Tiffen Road and follow to the end at Callaghan’s Rapids Road. Turn left on Callaghan’s Rapids Road and follow to the end. This road leads to the conservation area, bordering the Crowe River. There is no admittance fee or parking fee. Parking lot has space for up to 10 or 15 cars. ATVs and other motorized vehicles are not permitted in the Conservation Area, except by permit on the Trans-Canada snowmobile trail.
Sources
The Crowe Valley Conservation
Ontario Conservation
Ontario Beneath Our Feet (Geologic Curiosities of Canada)