Extension Ridge as a whole is simply termed "The Abyss" by mountain bikers, who've set up some fun wooden playgrounds in the area.
There are also petroglyphs, though not by the fissure. Maybe the petroglyphs predate the chasm?
Extension is a village southwest of the Cinnabar Valley. It was once a dynamic site for mining, especially in the second half of the nineteenth century. In fact, it rivalled the town called Nanaimo in its time.
Extension Ridge can be imagined to rise from the south bank of the Chase River, like at the Colliery Dams, and runs south between Nanaimo Lakes Rd and the Cinnabar Valley. You can see it from downtown - if you go to the top of Albert Street, look south across Harewood. The ridge is conspicuous enough, as a hill that is distinct from Mt Benson. You may be able to see the powerlines on it.
Back to the list of Nanaimo hiking spots
Zoom right in on the map below and you can see this great crack in the ground. (Open the link above the map if you have Google Earth.)
Park under the power lines on Harewood Mines Rd and walk south under the powerlines for about 100m, until you see some stairs leading up to the right. Climb the stairs and then stay to the right for about 15 minutes – it's hard to miss the earthquake fissure.
Open in Google Earth (kmz file)