Big Rock, Small Cave EarthCache
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Formerly known as the “Big Rock”, Monterey Rock was used as a landmark for early settlers, traders and Native Americans. Originally the rock was some 70 feet high, but it was used for building materials in the early years. In fact the very first settlement was nearby, when Joshua Holmes, William Holmes Jr., John Inman, George Fulmer and Milo Jones built a cabin opposite the Big Rock in October 1835.
The river here was forded, known simply as the Big Rock Ford. Other settlers joined them later that year, with Thomas Holmes setting out the village of Rockford a month later, now the Forth Ward of the city. But prior to that settlement, there was a naturally occurring shelter available to travellers – the cave in the rock itself.
Formation of the cave
There are several ways that a cave can form. These depend on the location and a range of environmental factors. Here is a description of two of those types:
Littoral caves
Also known as a sea cave, these caves are formed mostly through wave action against the rock surface resulting in erosion. The location is determined by a weak spot in the rock itself, which allows for greater wear than the surrounding areas. While these types can commonly be found at the current water level, they can also be found above sea level where the water level has since decreased. Some of the largest caves of these types can be found high above sea level.
Solutional caves
Some of the most commonly occurring types of caves, solutional caves are formed when the host rock is dissolved after a chemical reaction in groundwater or rainwater creates carbolic acid which eats away at the stone. While most frequently seen in limestone, they can also be found in other types of rock including dolostone, marble and gypsum. This formation is similar to the process seen in chemical weathering, although that is a larger term for a variety of chemical processes.
Questions
1. Estimate the height and width of the cave from your viewpoint.
2. If the cave is a littoral cave, what do you think had to be different in the past for it to have formed in this manner?
3. If the cave is a solutional cave, does that mean that the cave continues to grow? Explain your answer.
4. Now that you’ve considered these two types of cave formation, do you think the cave in Monterey Rock is a littoral or solutional cave?
Photographs at the site are always appreciated. Please submit answers via email/messenger to me. No spoilers/answers in your logs please.
Postcard image courtesy of the Hedberg Public Library.
Additional Hints
(No hints available.)