Welcome to my Earthcache! An Earthcache is a special type of geocache where there is no container to find - instead you are looking for a unique geological feature of the area and need to answer questions, as well as posting a picture, in order to claim the find. The goal of this Earthcache is to educate visitors about tufa and how to identify them, how they develop and what makes them interesting.
The tufa you are looking for is located in approximately a 90 square meter area around the posted coordinates, near a calcicolous stream. The trail getting to the point can be fairly steep and slippery, and yopu may need to wade in ankle deep water to make your observations. I am rating this earthcache for the "worst case scenario" during the wet spring season when this cache was placed - you mileage and experience may vary depending on the time of year and amount of rainfall we have at the time of your visit.
EARTHCACHE REQUIREMENTS
As with all of my ECs, I am not looking for PhD thesis level responses, but I am hoping that you take some time to enjoy the area and learn something new. This is not your typical 1.5/1.5 earthcache and you will need to make some calculations, bring a specific tool with you (pH paper, available from most pet stores and hardware stores for less than $5.00) in order to complete the lesson. Those who do not complete the EC as intended may have their logs deleted without notice. Please include a list of all cachers with your answer, if answering for more than one caching name, but note that each cacher must upload their own photo to their log.
To claim a 'find' for this Earthcache you must answer the following questions and send your answers in a message or email to the owner using the link at the top of the page. You can log your find with a photo at GZ. Send your answers to the tasks. I will be in contact if there is a problem, no need to wait for a response as long as the required photo is included in your log.
Questions to Answer:
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Describe the appearance of the tufa at the site. What textures or features can you see? Does the rock look uniform or does it contain visible voids or plant impressions? Are the pieces you fee fairly large or are they broken and fragile? Estimate the total percentage of tufa vs other rock at the site.
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Explain the process that causes tufa to form here. In your own words, describe how groundwater chemistry leads to tufa precipitation at the surface, and determine if you think that the tufa will continue to develop here given the current conditions.
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Based on your observations and the information above, why is this location ideal for tufa formation? Consider the geology, groundwater source, and landscape.
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Using pH test strips (available from your local pet store or hardware store), provide the pH reading of the water here in the stream. Based on your reading from the stream and the information provided in the description, do you think that the area surrounding this sctream contains a high percentage of lime? Why or why not?
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Photo: Mandatory: Include a photograph of yourself, your GPS, a signature item, thumbs up, with a piece of tufa included in the photograph. You do not need to show your face in the photo, but your photo must be unique to you. Each log must include their own photo.
Earth Science Learning Focus
At this EarthCache, you will explore a rare tufa deposit located in Paris, Ontario. Tufa is a type of freshwater calcium carbonate deposit, and the Paris site offers a unique glimpse into how geological processes and groundwater chemistry shape the landscape. Through direct observation, you'll investigate how calcareous groundwater interacts with surficial deposits and the geologic history of the region to form this porous, fragile rock.
What Is Tufa?
Tufa is a soft, porous rock composed primarily of calcium carbonate (CaCO₃), which forms when calcium-rich, carbon dioxide-saturated groundwater discharges at the surface. As the water emerges, carbon dioxide degasses, decreasing the solubility of calcium carbonate and triggering the precipitation of the mineral calcite. Over time, this builds up deposits of tufa.
Tufa is chemically similar to limestone but distinct in texture—it is lightweight, fragile, and contains visible voids or plant impressions. Its porosity allows mosses and specialized calcicolous (lime-loving) plants to colonize its surface, although such plant life is not the focus of this lesson.
Geological Context of the Paris Tufa Site
Bedrock Geology
The bedrock underlying Paris consists primarily of calcareous Paleozoic sedimentary rocks. These rocks include abundant limestone and dolostone (also called dolomite), which are rich in calcium carbonate and highly reactive with groundwater.
Key calcareous formations in the area include:
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Dundee Formation (limestone)
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Lucas and Amherstburg Formations (dolostone and limestone)
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Salina Formation (dolostone and evaporites like gypsum)
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Guelph and Amabel Formations (fossil-rich dolostone)
These rocks contribute calcium and carbon dioxide to infiltrating groundwater, setting the chemical stage for tufa formation.
Surficial Geology
Above the bedrock lies a mix of glacial tills, sands, silts, and river-deposited materials formed during and after the last ice age (<45,000 years ago). Of particular importance is the dark green-colored till unit, a glacial deposit likely derived from erosion of local calcareous bedrock.
This till unit is critical because:
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It is the source of the groundwater seep where tufa forms.
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It supplies calcareous material that enriches groundwater in calcium and CO₂.
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It provides the physical setting (slope and drainage conditions) for the tufa terraces.
Description of the Tufa Features
At this site, you will see:
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Loose tufa blocks with porous textures and occasional plant casts.
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Step-like terraces of tufa, formed where surface water flows over sloping ground.
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White calcite crusts on mosses and rocks near active groundwater seeps, indicating ongoing calcite precipitation.
The presence of tufa here reflects a dynamic interaction between groundwater chemistry, slope conditions, and surface water movement. In places, where the land gradient appears to be steeper, and farther away from the groundwater discharge site, stepped tufa terraces are developed. The height of each step is about 20 cm or less. The stepped tufa is located close to the transition to low-slope wetland. Precipitates of crusty white material, presumed to be calcite, locally coat vegetation, such as moss, in areas where the surface water flow is continuous.
Resources:
Paris (Ontario) Tufa Plants
Tufa (Science Direct)
Tufa
This cache was placed by a PROUD Platinum Earthcache Master.
