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When Clinker Peak erupted the lower part of Rubble Creek valley was still filled with ice and where the ice and lava met in what must have been a spectacular outburst of steam explosions the lava front was quenched and deflected. In 1855, long after the ice had disappeared, its oversteepened, unstable snout collapsed, triggering a massive rockslide. The headwall of that slide, now known as The Barrier, is still considered by many to be a potential hazard. Mathews, the guy who identified the origin of the Barrier, was among the expert witnesses in a court case that assessed the risk and ruled against any development on or adjacent to the Rubble Creek slide.
Bill Mathews passed away in 2003 but his pioneering work on Mount Garibaldi paved the way for many others who continue adding to our knowledge of the Volcanic Belt as a whole. Modern isotopic dating has given us the ages of individual volcanoes. The nature of past eruptions has been interpreted from the morphology and chemistry of the lavas, and detailed regional mapping has provided a link to global tectonics. But there is still much more to learn.
Not all the Garibaldi Belt volcanoes share Mount Garibaldi's brief, eventful history. Many of them, like the Black Tusk, were already dormant by the time the Fraser Glaciation began. Others were born and died beneath the ice and, despite their common Juan de Fucan heritage, the life of each volcano is a unique blend of nature and nurture the chemical "DNA" of its parent magma, and its encounter with the surface world.
My favorite volcanoes: Mount Fee, Mount Cayley, and Ring Mountain are all visible from the ski slopes but, because they are hard to reach, their pristine alpine meadows nestled against a backdrop of dramatic cliffs and spires must be among the most awesome campsites in the world. From the top of Whistler it's 25 km to Mount Fee and nearby Mount Cayley, but even at that distance their incredibly steep serrated profiles are an imposing sight against the western skyline. Too precipitous to hold snow, the bare rock of their jagged upper slopes contrasts with the rounded, snow-covered summits of surrounding granitic peaks.
The present form of Mount Cayley is probably fairly close to its original shape. The eruption of thick, viscous lava flows was accompanied by the extrusion of near-solid domes that shouldered aside the surrounding granite and expanded like spring mushrooms forcing their way through the forest litter. The first hot, semi-rigid lava broke through the surface about 3 million years ago and grew into the crumbling spine of rock that now forms the summit of Mount Cayley. Other eruptions followed, forming the precipitous spine of Vulcan's Thumb and two smaller domes, the youngest being about 300,000 years old.