Safety and Access:
- The Galloping Goose Trail is a public multi-use path. Watch for cyclists and other users.
- Do not hammer, chip, or damage the rock—observe only.
- Some rock faces may be steep or slippery; keep a safe distance.
- From Parking coordinates, GZ is a 10 minute walk or 3 minute bike ride on a flat, well-maintained trail.
Walking or cycling along the Galloping Goose Trail in the Sooke area, you might notice the exposed dark, blocky rocks along the cut slopes. These aren’t ordinary rocks—they are part of the Metchosin Igneous Complex (MIC), a rare and remarkable geological feature that represents a section of ancient oceanic crust and upper mantle that has been lifted from the seafloor and placed here on land.
This kind of rock body is called an ophiolite. It gives geologists a rare, direct look at the type of crust that forms beneath our oceans—without having to drill through thousands of meters of seawater and sediment. The MIC is one of the few places in the world where you can see such rocks so well exposed.
Logging Tasks
To claim this EarthCache 
, you must first visit the posted coordinates and then Send Answers via the geocaching.com Message Center to the following questions based on your observations and the information provided in the short Earthcache Lesson below:
- Describe the appearance of the bedrock at the coordinates. What is its color, texture, and any visible structures?
- Look for evidence of volcanic origin—do you see pillow shapes, fractures, or mineral crystals?
- Based on your observations of the rocks and its influence on vegetation, explain why these rocks are interpreted as part of an ophiolite sequence.
- (Optional) Take a photo of yourself or your GPS at the site without revealing answers.
Earthcache Lesson: What is the Metchosin Igneous Complex?
The MIC is part of what geologists call the Crescent Terrane, a block of oceanic crust formed around 50–56 million years ago during the Eocene epoch. Back then, this crust was created at a spreading center—possibly in an island arc or near-ridge volcanic setting—where magma rose from the mantle, cooled, and solidified into a variety of igneous rocks.
The complex contains several distinct rock types, often stacked in layers that mirror the structure of ocean crust:
- Basalt flows – Dark volcanic rock that formed from lava erupted onto the seafloor. These flows often show pillow structures—rounded blobs that form when lava cools rapidly under water.
- Sheeted dikes – Vertical or near-vertical slabs of rock that once served as conduits for magma moving up from deeper in the crust to the seafloor.
- Gabbro – Coarse-grained, slowly cooled magma that solidified deeper in the crust.
- Minor sediments and tuffs – Bits of volcanic ash and marine sediments caught between flows.
The presence of all these components in one area is one of the clues that helped geologists recognize the MIC as part of an ophiolite sequence.
How Did Ocean Crust Get Here?
The MIC didn’t form where you see it today. Instead, it originated far offshore on the Kula Plate, a now-vanished tectonic plate in the Pacific Ocean. Through plate tectonic processes, this oceanic crust was transported toward the edge of North America.
Around 50 million years ago, the Kula Plate was being subducted beneath the continent. In this case, part of the oceanic crust didn’t get dragged into the mantle—it was instead scraped off and welded onto the edge of the continent, a process called accretion. Over time, uplift and erosion exposed the MIC at the surface.
The Galloping Goose Trail Outcrops
Along this section of the trail, the bedrock is dominated by MIC volcanic rocks—mainly basalt and sheeted dikes. The rocks are often massive, dark gray to greenish, and may have visible mineral crystals such as plagioclase feldspar or pyroxene. In some areas, you might see:
- Pillow basalt shapes if the outcrop has been freshly exposed.
- Fractures and joints from tectonic stresses over millions of years.
- Glacial scratches on the rock surface from the last Ice Age.
Because the MIC is very hard, it resists erosion better than many surrounding rocks, influencing the trail’s landscape and drainage patterns. This can be observed in the type of vegetation that grows here compared to the typical dense, coniferous forests of the Pacific Northwest.
Related Geological Features
While the EarthCache focuses on the MIC, the surrounding geology adds context:
- Sooke Formation (deposited 23 to 25 million years ago)– In a few pockets nearby, sandstone and conglomerate from this younger formation unconformably overlie the MIC.
- Leech River Fault – Not far to the north, this fault marks the boundary between the MIC (Crescent Terrane) and metamorphic rocks of the Leech River Complex.
- Quaternary deposits – Glacial till and clay from the last ice age cover some low-lying areas.
The MIC is significant because it:
- Preserves a nearly complete section of oceanic crust.
- Provides evidence of past plate tectonic processes in the Pacific Northwest.
- Helps scientists compare ancient ocean crust with modern ocean floor drilling results.
- Influences local topography, hydrology, and even vegetation patterns.
References for Further Reading
- BC Ministry of Energy, Mines and Petroleum Resources – Bedrock Geology Map:
https://cmscontent.nrs.gov.bc.ca/geoscience-publications/Bedrock_Geology_of_BC.pdf
- Geology of Vancouver Island (UVic Earth and Ocean Sciences):
https://web.uvic.ca/~mrempel/geol_van_island/
- Geological Survey of Canada – Crescent Terrane Overview:
https://www.nrcan.gc.ca/earth-sciences
- “Metchosin Igneous Complex, southern Vancouver Island, British Columbia” (Roddick & Woodsworth, Geological Survey of Canada Paper 87-2):
https://doi.org/10.4095/122344
- Cascadia Subduction Zone information – USGS:
https://earthquake.usgs.gov/learn/topics/csz.php