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A large (ca. 5 × 106 m3) landslide occurred on the west flank of Mount Cayley in the southern Coast Mountains of British Columbia in 1963. Failure commenced when a large block of poorly consolidated tuff breccia and columnar-jointed dacite was detached from the subvolcanic basement and slid into the valley of Dusty Creek, a small tributary of Turbid Creek. As the detached block accelerated, it quickly fragmented into an aggregate consisting of angular clasts up to several metres across, partially supported by a matrix of fine comminuted rock material. The landslide debris moved about 1 km down Dusty Creek as a wedge-shaped mass up to 70 m thick, banking up on turns and attaining a maximum velocity of 15–20 m/s. The debris mass thinned as it spread across the broader, flatter valley of Turbid Creek, and was deposited as an irregular blanket with a maximum thickness of 65 m along a 1 km length of this valley. As a result of the landslide, Turbid and Dusty Creeks were blocked, and lakes formed behind the debris. These debris dams were soon overtopped and rapidly breached, causing floods and probably debris flows to sweep down Turbid Creek valley far beyond the terminus of the landslide.From an analysis of the annual rings of slide-damaged trees, it is concluded that the landslide probably occurred in July 1963. Although the largest earthquake of 1963 and a moderately intense rainstorm also occurred during this month, there were much larger earthquakes and storms in this area on many previous occasions, and these did not cause large slope failures. Thus, it appears that the stability of the slope at the head of Dusty Creek gradually deteriorated over a long period of time until a relatively minor event, such as a small earthquake or storm, triggered the failure.The main contributing factors to this landslide are geologic and include the presence of: (1) hydrothermally altered faults and fractures in poorly lithified pyroclastic rocks and in jointed volcanic flows; (2) an outward-sloping unconformity separating the Quaternary volcanic sequence from older basement rocks; and (3) fractured glassy selvages surrounding small intrusions in the base of the volcanic pile.Deposits of one or more landslides that predate the 1963 event also occur in Turbid Creek valley. These older deposits are present over a much larger area than the 1963 slide deposits and probably were emplaced by highly mobile debris flows with high water content.

Terrestrial heat flux was measured in fjords, in boreholes, and in offshore wells at sites across the convergent margin of southwestern British Columbia from the continental shelf landward to the Garibaldi Volcanic Belt. Temperatures in the offshore wells were corrected for drilling disturbances, and formation thermal conductivities were modeled using measurements on cuttings and downhole geophysical logs. Marine measurements in the fjords were corrected for the large effects of refraction as well as aperiodic temperature variations in the bottom waters. There was excellent agreement between marine measurements and those from nearby onshore boreholes. The heat flux above the subducting Juan de Fuca plate steadily decreases landward from over 50 mW m−2 on the shelf to 25 mW m−2 seaward of the Garibaldi Volcanic Belt. An abrupt increase to 80 mW m−2 over a distance of 20 km is centered 30 km seaward of the volcanic zone. Very large variations in heat flux occur locally within the Pleistocene volcanic area, the result of advective cooling of intrusive magmas. The measured heat generation of crustal samples along the entire profile is low, 0.6–0.8 μW m−3. A landward dipping, seismically reflective zone above the subducting oceanic plate beneath Vancouver Island appears to be nearly profile is low, 0.6–0.8 μW m−3. A landward dipping, seismically reflective zone above the subducting oceanic plate beneath Vancouver Island appears to be nearly isothermal. It is postulated that dehydration of the subducting oceanic crust at and above approximately 450°C absorbs heat and produces water which flows updip along this zone in the overlying subduction complex, effectively redistributing the heat seaward to where the water is reabsorbed in hydration processes. A relatively cool crustal wedge lies above the deeper subducting oceanic crust, and at its thick, landward side the abrupt increase in surficial heat flux must be caused by a shallow (10 km depth) heat source produced by ascending magma.

The Clearwater – Wells Gray area of east-central British Columbia includes a succession of late Cenozoic, alkali olivine basalt flows that lie east of the extensive Chilcotin lavas and define the eastern end of the Anahim Volcanic Belt. The rocks are petrographically similar to but less altered than the Chilcotin basalts. The volcanic activity spanned at least two episodes of glacial advance and produced both subaerial flows and a subaqueous facies comprising pillow lava, pillow breccia, and tuff breccia, locally intercalated with fluvial gravels and sand. Four morphological assemblages have been recognized. An early glacial assemblage, characterized by tuyalike forms, gives K – Ar dates of 0.27 – 3.5 Ma. These circular features are surrounded by a deeply dissected valley-filling assemblage of subaerial and minor subaqueous flows and tuff breccia that rest locally on lag gravel and till. Subaerial flows in this assemblage give K – Ar dates of 0.15 – 0.56 Ma. Whitehorse Bluffs, a volcanic centre composed of crudely laminated tuff cut by high-level dykes, may be a source of some of these valley-filling flows. A late interglacial assemblage is composed of subaerial pyroclastic material, transitional deposits, and deposits that are clearly subaqueous. Volcanic activity in the area culminated with the formation of pyroclastic cones, blocky lava flows, and pit craters that postdate the last Cordilleran glaciation.