Welcome to my Earthcache!
An EarthCache is a special type of geocache where there is no container to find. Instead, you explore a unique geological feature and answer questions to claim your find, along with posting a photo. This EarthCache is part of the Kitchener Rock Walk, which explores geological features within downtown Kitchener. These earthcaches are designed to be done on foot, walking around the downtown core and exploring a variety of different features as seen on different buildings.
This EarthCache focuses on the black volcanic stone used at Speaker’s Corner and in the seating along King Street in downtown Kitchener. Although Ontario itself has no active volcanoes, this rock connects the city streetscape to volcanic processes occurring thousands of kilometres away in Hawaii.
Access Notes
This EarthCache is located in a public pedestrian area and can be completed entirely from sidewalks and seating areas. Please be respectful of the space and other visitors. Do not climb, scratch, or damage the stone. All observations must be visual only.
EARTHCACHE REQUIREMENTS
To log this EarthCache, you must visit the site and complete all logging tasks listed below. Your answers must be based on your own observations made at the location. Logs that do not adequately address the questions or that are missing the required photograph may be deleted.
Examine the black stone closely. Observe its colour, grain size, surface finish, and any visible features such as tiny holes, subtle layering, or mineral crystals. Compare it mentally to other stones used nearby (some of the other Kitchener Rock Walk Earthcaches may give you a starting point for your comparison), such as granite or limestone, and note what makes this rock stand out.
Logging Questions
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Describe the colour and surface finish of the volcanic rock. Is it uniformly black, or do you notice variations in tone or texture?
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Can you see individual mineral grains with the naked eye, or does the rock appear very fine-grained? What does this suggest about how it cooled?
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Do you observe any small holes or pits in the stone? If so, what might have caused them?
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How does this volcanic rock look and feel different from granites or limestones you may have seen elsewhere in downtown Kitchener?
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Mandatory: Post a photo of yourself or a personal item (such as a GPS or notebook) with the large Speakers Corner carved mural visible in the background. The photo does not need to show your face but must be unique to you.
Geology Lesson: Hawaiian Volcanic Rock
The black stone used at Speaker’s Corner is a fine-grained volcanic rock most commonly known as basalt. Basalt forms from magma that erupts at the Earth’s surface as lava and cools very quickly. Because the lava cools so rapidly, mineral crystals do not have time to grow large, giving basalt its smooth, dense, and fine-grained appearance.
In Hawaii, basalt is produced by volcanoes formed over a mantle hotspot—a place where hot material rises from deep within the Earth. Lava eruptions there are frequent and fluid, allowing basaltic lava to flow easily before solidifying. Most Hawaiian basalts are geologically young, often less than a few million years old, and some are still forming today.
Volcanic rocks like basalt are rare in Ontario because the province sits in the stable interior of the North American tectonic plate, far from active plate boundaries and hotspots. Ontario’s bedrock is dominated by very old igneous and metamorphic rocks formed deep underground billions of years ago, along with sedimentary rocks deposited in ancient seas. Surface lava flows, like those in Hawaii, simply do not occur here.
Basalt differs strongly from rocks typically found in Canada’s urban buildings. Unlike granite, which cooled slowly underground and has visible crystals, basalt cooled quickly at the surface and appears uniformly dark and fine-grained. Unlike limestone, basalt is not made from shells or sediments and contains no fossils. Its dark colour comes from iron- and magnesium-rich minerals such as pyroxene and olivine.
Basalt also provides an important link between volcanism and plate tectonics. Most basalt on Earth forms along plate boundaries, especially at mid-ocean ridges where tectonic plates move apart and magma rises to fill the gap, creating new oceanic crust. In contrast, Hawaiian basalt forms above a mantle hotspot, where a plume of hot material rises from deep within the Earth while the tectonic plate slowly moves overhead. This creates a chain of volcanic islands rather than a linear plate boundary. The presence of Hawaiian basalt here highlights the difference between boundary-driven volcanism and hotspot volcanism, helping explain why volcanic rocks can form in some places far from plate edges, yet are absent in stable regions like Ontario.
Basalt is often used in architecture and urban design because it is very strong, resistant to wear, and can be polished to a smooth, reflective finish. Its dark colour absorbs light and creates strong visual contrast with lighter stones. At Speaker’s Corner, this volcanic rock brings a piece of active Earth processes—normally associated with oceanic islands like Hawaii—into the heart of downtown Kitchener, offering a rare glimpse of magma-formed rock in an Ontario streetscape.
AI Content Disclosure: Some of the descriptive text was created with assistance from AI tools. All information has been reviewed and verified by the cache owner for accuracy.
This cache was placed by a PROUD Platinum EarthCache Master.
