🌎 Rothsay Dolomite Pond
Location: Gage Park, Hamilton, Ontario, Canada
Cache type: EarthCache (no physical container)
🪨 Earth Science Lesson
Beneath your feet in Hamilton lies an important geological foundation: dolostone and limestone bedrock.
These carbonate rocks were formed more than 400 million years ago during the Silurian and Devonian periods, when this region was covered by warm, shallow seas.
Both dolomite (calcium magnesium carbonate) and limestone (calcium carbonate) are slightly soluble in rainwater, which becomes weakly acidic as it absorbs carbon dioxide from the air.
Over thousands of years, this process creates cracks, pores, and small channels within the rock—features that make it permeable and capable of allowing water to slowly move through it.
This property of the local bedrock plays a vital role in Hamilton’s stormwater management systems.
At the Rothsay Avenue Flood Remediation Project, rainwater is directed into this specially designed stormwater pond, where it can temporarily collect, filter, and gradually infiltrate downward through soil and dolomite layers into the groundwater system.
By working with the natural geology instead of against it, engineers have reduced flooding, improved water quality, and mimicked natural hydrologic cycles in an urban setting.
This site demonstrates how geology influences how cities handle rainfall and runoff.
🌍 Geological Background: Hamilton and the Niagara Escarpment
Hamilton sits on the edge of the world-famous Niagara Escarpment, a ridge of dolostone and limestone bedrock that stretches from Niagara Falls through Hamilton and northward into the Bruce Peninsula.
This rock layer was formed about 420–430 million years ago during the Silurian Period, when southern Ontario lay beneath a shallow tropical sea.
Over time, sediments of calcium carbonate (from coral, shell fragments, and marine organisms) built up on the sea floor and hardened into limestone.
Later, magnesium-rich groundwater partially replaced some of the calcium in the rock, transforming it into dolostone—a more erosion-resistant form of limestone.
The fractures and solution channels within these carbonate rocks make them naturally porous and permeable, allowing water to move through them slowly.
This same property that shapes caves and sinkholes in the Escarpment also helps modern cities like Hamilton manage stormwater through infiltration and groundwater recharge.
🧭 Your Mission
Visit the interpretive sign titled “Why Is This Pond Here?” located beside the stormwater pond in Gage Park.
Observe the pond, nearby vegetation, and surrounding rock and soil conditions—especially after a rainfall event.
🧩 Logging Tasks
To log this EarthCache, please complete the following tasks and send your answers via private message or email (do not post answers in your log):
- Hydrology in Action:
According to the sign, what happens to the rainwater that falls in the Rothsay Avenue District before and after the flood remediation project? Summarize what changed.
- Flood Prevention Mechanism:
Describe at least two ways the stormwater pond helps reduce flooding and protect water quality in nearby neighborhoods. (Hint: check the section “What are the benefits of a stormwater pond?” on the sign.)
- Geological Connection:
Based on what you can see at the site and what you know about Hamilton’s dolostone and limestone bedrock, explain how these rock types help with stormwater absorption and filtration. Why are they effective materials for infiltration?
- Photo Requirement:
Take a photo of yourself or a personal item (such as a GPS, notebook, or hand) near the “Why Is This Pond Here?” sign or the stormwater pond itself.
💡 Educational Notes
This EarthCache combines hydrology and geology — showing how natural rock properties can be used to manage urban stormwater.
- Dolostone and limestone are both carbonate rocks that dissolve slightly in rainwater, forming porous networks that store and transmit water.
- Stormwater ponds act as temporary reservoirs, holding runoff during storms and releasing it slowly into the ground or sewer system.
- By filtering through soil and carbonate bedrock, water is naturally cleaned of sediment and pollutants before reaching Lake Ontario.
This partnership between geology and engineering strengthens the local ecosystem, reduces erosion, and helps maintain the natural water balance beneath Hamilton.
📸 Reminder
Include your required photo with your log. Logs without the answers or required photo may be deleted in accordance with EarthCache guidelines.
🧭 Credits
Information sourced from the interpretive sign “Why Is This Pond Here?” by the City of Hamilton, located at the Rothsay Avenue Flood Remediation / Gage Park Stormwater Pond.
Cache created for educational purposes under the Geocaching EarthCache program.