Equipment required: Flashlights, thermometer, ruler, change of clothes (you may get dirty/muddy crawling into the cave.)
The caves in Rockwood Conservation Area are another unique feature created by the runoff of the Wisconsin glacier. Within the conservation area you will find an extensive network of 12 solution caves. The erosion of sedimentary rock created this cave system when an underground stream flowed through the rock. The cave system is one of the most extensive systems found in Ontario and exhibits depositional features including stalactites, columns and flowstone.
History and Geology of the Rockwood Area
410 million years ago Rockwood was in the tropics. The days were only 20 hours long, because the world was spinning faster than today. Rockwood and most of southern Ontario was covered by a tropical inland sea. Rockwood was located in a shallow part of the sea where there was a thriving coral reef. The coral grew in pinnacles to the top of the water because it needed sunlight. It would die back when the water level fell. Mollusks, such as snails and clams, lived in among the coral. They are now extinct, but are ancient relatives of today’s edible shellfish. Over millions of years, their shells piled up eventually becoming limestone cliffs that are up to 36 metres tall.
Over 60 million years ago the continents started to collide. Gradually, the super continent Pangaea began to break apart. A piece of Pangaea, called Laurussia, began to drift north. During this change, the earth moved, volcanoes erupted and the landscape transformed. The climate changed completely and became very cold.
11,000 to 16,000 years ago was the peak of the Ice Age in the area. Instead of being covered by a tropical sea, Rockwood was covered by the Wisconsin glacier that was a kilometre thick. As it grew, the great glacier worked like a bulldozer, smashing everything in its way. The glacier was so large, it went from the Rocky Mountains to Newfoundland.
10,000 years ago the moderate climate began. Finally free of its heavy load of ice the earth’s crust began to rebound. This left bald limestone and water at Rockwood, as well as interesting rock formations that are visible today. First lichens appeared on the land and algae on the water. Together, they formed the first moss. Then ferns evolved, followed by grasses, wild flowers, shrubs and eventually soft wood.
Although the past thousands of years had the greatest impact of what we see today, one can even go back much further to 420 - 425 million years ago were the area was part of the Eramosa, a member of the Lockport Formation or rock, with gradational contacts with the Goat Island Member (area to the south) and the Guelph Formation (area immediately to the north). These among other formations are also part of the Lockport Formation. The rocks forming the Eramosa are mostly dolomites, but the composition varies from almost pure, grey-weathering, fine grained dolomite to shaly, bituminous, brown-weathing, bioturbated dolomites. Fossils are common at some localities, scarce at others, and chert is generally a minor component. The most characteristic feature is bituminous shaly interbeds. Probably the Eramosa was deposited in several related environments, most likely including shallow, restricted (and poorly oxygenated) marine waters which we see signs of being present here today in the valley outside of this cave.
Cave formation begins when rainwater absorbs carbon dioxide as it falls through the atmosphere. Rain water must have carbon dioxide to become acidic. It must be acidic to chemically react to the limestone bedrock. Rainwater is absorbed by the soil into the ground. As rainwater comes through the soil it absorbs more carbon dioxide that is being produced by plants that are dead. This changes the ground water to a weaker form of carbonic acid (H2O + CO2 = H2CO3). As it travels down through the ground it comes to solid rock. When the rock is limestone or dolomite caves can form. The water reacts chemically with limestone and slowly a larger and larger space will form. This happens because the rocks are made of calcium carbonate (CaCO3). This is what you call chemical erosion. As the space becomes larger and larger the water can flow through. As it flows it erodes . Physical erosion washes away rock and sand. This is what makes a cave larger and forms an underground stream. Finally over hundreds of thousands of years or even millions of years the cave is formed.
The above process of cave formation is how this particular cave has formed over time. The opening to this cave is small and then opens up into a chamber, then another small opening into a 2nd chamber. Examine the chambers' walls and ceilings and look for cracks and evidence of where the water seeps in and erodes the rock around it. Feel the rock and see if it's more soft and brittle than that of the smaller areas that you have to crawl through. If you come here in the winter, the opening may be blocked to some degree by ice stalactites formed by the water dripping down from within the opening of the cave and you may also notice water in the floor of the first chamber which you can observe the evidence that the water comes from both inside the caves dripping down though the cracks and also from outside of the cave that may flow inside during wet periods as the area outside of the cave is in a valley and there normally is a stream just a few meters from the cave opening.
Resident Cave Man
For 6 years during the 1980s there was a man who called this cave his home. He had his fire just inside the door of the cave and the smoke from the fire would exit through a 1 inch hole that he made to the outside. The ashes from his fire would fall down another hole which he made and then would be able to empty them. The park eventually sent him his eviction notice.
Access to the cave is from a side trail that takes you to the backside of an impressive set of limestone cliffs. Follow the side trail to get access to the valley on the other side and then follow the base of the cliff to the cave opening which you will find at ground level. It may be a bit muddy at times around the cave opening. There are some pieces of wood and an old car tire lining the ground to the entrance of the cave. It is a tight fit and you need to crawl in on your belly. Once inside, you will encounter a chamber which you should be able to stand in. Then in another tunnel at the back right within this chamber that leads to a 2nd chamber. Again you will need to crawl on your belly through this tunnel to access the 2nd chamber. In order to log this earthcache you will need to access both chambers in order to get the required information and make your observations.
Tasks and Logging Requirements
1) With the use of a thermometer, take the temperature at the outside of the cave, within the 1st chamber and then within the 2nd chamber. Make sure you let the thermometer adjust long enough at each of these 3 places so as to get an accurate reading. Many GPS's are able to take temperature readings too. On my unit when powered off, pressing the Power and Enter buttons simultaneously will power on the unit to a diagnostics screen that will show the temperature as one of the settings. What are the 3 temperatures you record and explain why you think the temperatures are as such.
2) Which chamber is bigger and which is taller? What evidence do you see that can support your answer related to how this cave was formed.
3) While in the chambers of the cave, examine the rock around you, looking for cracks or openings. How deep and how wide at the surface is the deepest crack or gap that you can find and is there evidence that water may flow through these cracks perhaps contributing one day to more tunnels and chambers being formed in this cave. How do you think this cave (or the surrounding area of limestone cliffs that houses this cave) will be changed in 500, 10,000, 100,000 or even a many millions of years?
4) Is there any ice formations in the cave? Describe. Is the ice transparent, translucent or opaque?
5) Within the 2nd chamber is a set of names along with a year. The first name is Joe. What is the 2nd name and what is the year.
Email me the answers to the above questions and then go ahead and log this earthcache. Feel free to post pictures too.
Activity You Can Try
Mix a mild acid (vinegar) with a base (baking soda). The reaction of the two substances illustrates the process of carbonic acid dissolving limestone. However actual limestone solution by carbonic acid is a weaker, less noticeable reaction.
** Please note that there is a fee to enter Rockwood Conservation Area. See additional waypoints for entrance location.