Volcanism still continues from time to time. Eruptions were most vigorous 610 million years ago (mya) and 23 mya, when most of the basalt was released. Smaller eruptions continued from 1.6 mya to 0.01 mya.
Garibaldi Volcanic Belt
The Garibaldi Volcanic Belt is the northern part of the Cascade Volcanic Belt. It is in British Columbia and the northwestern United States. Its volcanos are the most explosive in Canada.
The volcanoes are also the closest to British Columbia's densely populated southwest corner. These volcanoes are the result of subduction of the Juan de Fuca tectonic plate: the plates meet just seaward of the west coast of Vancouver Island. The volcanoes of the Garibaldi Volcanic Belt are stratovolcanoes typical of subduction zones, and include Mount Garibaldi, Mount Cayley and Mount Meager. Meager's eruption 2,350 years ago is the youngest explosive eruption in Canada. It was similar to that of Mount St. Helens in 1980 and the ongoing eruption of Montserrat in the Caribbean.
Mount Garibaldi
Mount Garibaldi is an eroded, dacitic strato volcano in southwestern British Columbia. Both Garibaldi and Mount Baker to its south are part of the Cascade volcanic arc. Mount Garibaldi, 80 km due north of Vancouver, is made up of Mount Garibaldi, Atwell Peak,and Dalton Dome. This Pleistocene volcanic center is part of a volcanic field that contains some 13 vents in an area 30 km long by 15 km wide, much of which is in Garibaldi Provincial Park.
The eruptive history of Mt Garibaldi involves an initial period of volcanism (200,000-300,000 years ago) followed by a period of quiescence. Renewed activity in the last 50,000 years has rebuilt the edifice in a series of violent eruptions, like when Mount Pelee erupted in 1902 and destroyed the town of St. Pierre on the island of Martinique. As successive pyroclastic flows travelled down the mountain's gentle slopes and were deposited, the volcano took on a broad, conical form. Part of the volcano's southwest flank built out onto thick glacial ice filling the Squamish River valley. Subsequent rapid melting of the ice at the close of the last ice age removed support from the western part of the cone. The volcano collapsed,producing much of the existing rugged topography of Mount Garibaldi and Atwell Peak. This catastrophic failure left a scarp on which is exposed the internal structure of the volcano and a debris fan with an estimated volume of 150,000,000 m at the foot of the mountain north of the town of Squamish. As valley glaciers retreated, two lava flows erupted Clinker Peak, immediately north of Mt. Garibaldi. The northernmost Rubble Creek flow was party confined by a wall of ice, resulting in a lava flow over 244 m (800 ft) thick. The steep, northern edge of the Rubble Creek flow party collapsed several times, most recently in 1855-1856; the village of Garibaldi was abandoned because of the danger of future collapses. The most recent period of activity occurred shortly after the disappearance of the glacial ice filling the valley, 10,700 to 9,300 radiocarbon years ago, and ended with the eruption the Ring Creek lava flow from Opal cone on Garibaldi's southeastern flank.
The Ring Creek flow is very unusual. It is 15 km long - a length usually only attained by basalt flows,except that the Ring Creek flow is dacite. Renewed volcanism in the Garibaldi area would pose a serious threat to the local communities of Whistler and Squamish. Although no
Plinian-style eruptions are known, even Pelean-type eruptions could produce large quantities of ash that could rise to several hundred meters above the volcano. As it is close to Vancouver, this would make it a hazard for air traffic. The danger from lava flows would be low to moderate because the nature of the lavas would prevent them from travelling far from their source,even though the Ring Creek lava flow ends only 6 km from Squamish. Melting of remnant glacial ice capping the Mt. Garibaldi area could produce floods, lahars,or debris flows that might endanger small communities including Brackendale.
Highway 99, which links Whistler and Squamish with Vancouver, is already plagued by landslides and dedris flows from the precipitous Coast Mountains. An eruption producing floods could destroy segments of the highway. Flooding and debris flows could also have serious coneequences for the salmon fishery on the Squamish, Cheakamus, and Mamquam rivers. In addition,explosive eruptions and the accompanying ash could cause short and long-term water-supply problems for Vancouver and much of the lower mainland. The catchment area for the Greater Vancouver watershed is downwind from the Garibaldi area. Air-fall material could also have a deleterious effect on the ice fields to the east of Mt. Garibaldi, causing increased melting and spring flooding. This in turn could theaten water supplies from Pitt Lake as well as fisheries on the Pitt River.
Mount Meager
Mount Meager is a potentially active volcano in the Canadian province of British Columbia, Canada, 150 kilometers north of Vancouver. The top of the mountain is mostly covered by snow and glaciers. It lies in the Garibaldi Volcanic Belt and is the northernmost volcano of the Cascade Volcanic Arc that extends down to northern California. Its most common type of rock is lava that is almost a million years old (with a thickness in some places over 1 km).
The mountain is part of the Pacific Ranges of mountains and is 2,680 meters (8,793 feet) high. It was previously called "Cathedral Mountain".
Meager is known for its last major eruption about 2,350 years ago. The strange thing about the eruption was the fact it released the debris from the northeast side of the volcano, as rock and ash blocked a major river called the Lillooet River. The river was dammed to a height of at least 100 meters, forming a lake. The lake reached a maximum elevation of 810 meters and was at least 50 meters deep. The breccia soon eroded from water activity within the lake, forming Keyhole Falls. There was a massive flood when the water first broke through the breccia, carrying small house sized blocks of breccia. During this eruption, ash was hurled into the air over 20 kilometers above sea level. The ash was carried eastward as far as Alberta.
Meager is an unstable volcano. It is built of unstable volcanic and has dumped clay and rock several meters deep into the Perberton Valley at least three times during the last 7,300 years. Two earlier debris flows, around 4,450 and 7,300 years ago, sent rubble at least 32 kilometers from the volcano. Recently, the volcano has created smaller landslides about every ten years, including one in 1975 that killed four geologists near Meager Creek. Logging, mining, tourism and wilderness recreation on nearby slopes and valleys are vulnerable to the volcano’s excellent geomorphic activity. The possibility of Mount Meager covering settled parts of the Pemberton Valley in a debris flow is estimated at about one in 2400 years. There is no sign of volcanic eruptions with these events, however scientists warn the volcano could release another massive debris flow over populated areas anytime without warning.
The explosive nature of past eruptions at Mount Meager indicates that this volcano also poses a considerable long-distance treat to communities across southern British Columbia and Alberta. It is also a local treat to the town of Pemberton, British Columbia, about 50 km away. Another explosive eruption at Mount Meager would also have a considerable impact on local mining and logging operations, as well as significant negative impacts on the Lillooet River fishery.
Metaphysics
Metaphysics is a major branch of philosophy. It concerns existence and the nature of things that exist. Altogether it is a theory of reality.
Ontology is the part of metaphysics which discusses "what" exists: the categories of being. Apart from ontology, metaphysics concerns the "nature" of, and "relations" among, the things that exist.