Recently, while showing around a friend from out of town, we visited Queen Elizabeth Park in Vancouver. My wife mentioned that it was volcanic. I did not know this. I figure my excuse is that I did not grow up here. It made me wonder if all those bridal parties you see in the summer time might one-day fall into a soup of molten lava.
The little mountain in Queen Elizabeth Park known as Little Mountain was indeed the result of volcanic activity, but the cavity that now contains the gardens, was not the cone of a volcano. It is the result of the Little Mountain Quarry which dug up the basalt for building the roads in Gastown, around a hundred years ago.
Vancouver Geology (JE Armstrong, 1990) which the Geological Association of Canada offers as a free PDF, reports that the volcanic activity that resulted in Little Mountain was part of the Cascade volcanism, which occurred between 31 and 34 million years ago, in the period known as the Oligocene—long after the dinosaurs had left the scene.
Warren Wulff, the very helpful library manager for the Natural Resources Canada library, informed me that geologists have differed in their interpretation of what happened. He explained that the columns, formed in the basalt, show patterns of cooling, but they seem to provide conflicting hints about what happened. It may have involved repeated events. It could be a sill, in which the magma (underground molten rock) spreads between layers of other rock, like a sandwich. Or it could be a flow, which would mean the lava (above-ground molten rock) flowed down over the surface of other rock. A map of Vancouver Geology, however, labels it as a dyke, in which case the magma would have cut across layers of other rock.
In any case, this volcanic intrusion formed a slab of igneous basalt that was harder than the surrounding sedimentary rock which was more easily worn away by glaciers and other weathering, leaving the Little Mountain as a lookout for tourists and a nice place to take wedding pictures.
For more on the amazing natural structures of our continent, make sure to watch America Wild: National Parks Adventure in our OMNIMAX Theatre.