The four-million-year-old Garibaldi Volcanic Belt, a north-south trending zone of volcanoes and volcanic rock in the southern Coast Mountains of southwestern British Columbia, can be grouped into at least three enechelon segments, referred to as the northern, central, and southern segments. The northern segment overlaps the older Pemberton Volcanic Belt at a low angle near the Mount Meager massif where Garibaldi Belt lavas rest on uplifted and deeply eroded remnants of Pemberton Belt subvolcanic intrusions and combines to form a single belt. A few isolated volcanoes northwest of the Mount Meager massif, such as Silverthrone Caldera and Franklin Glacier Complex, are also grouped as part of the Garibaldi Volcanic Belt. However, their tectonic origins are largely unexplained and are a matter of going research. When the Farallon Plate ruptured to create the Nootka Fault between five and seven million years ago, there were some apparent changes along the Cascadia subduction zone. At issue is the current plate configuration and rate of subduction but based on rock composition is for Silverthrone Caldera and Franklin Glacier Complex to be subduction related. The roughly circular, wide, deeply dissected Silverthrone Caldera in the northern segment of the Garibaldi Volcanic Belt, was formed one million years ago during the Early Pleistocene period. The bulk of the volcano was erupted 0.4 million years ago, but younger phases, consisting of lava flows and subsidiary volcanoes with compositions of andesite and basaltic andesite are also present. Mount Silverthrone, an eroded lava dome on the northeast edge of Silverthrone Caldera, was episodically active during both Pemberton and Garibaldi stages of volcanism. The eroded Franklin Glacier Complex just to the southeast consists of dacite and andesite rocks that range in age from 3.9 to 2.2 million years old. Southeast of Franklin Glacier Complex, the Bridge River Cones comprise remnants of both andesitic and alkali basalt cones and lava flows. These range in age from about one million years old to 0.5 million years old and commonly display ice-contact features related to subglacial eruptions. The Mount Meager massif, the most persistent volcano in the northern portion of the Garibaldi Volcanic Belt, is a complex of at least four overlapping stratovolcanoes made of dacite and rhyodacite that become progressively younger from south to north, ranging in age from two million to 2,490 years old. The central segment of the Garibaldi Volcanic Belt is defined by a group of eight volcanoes on a ridge of highland east of the Squamish River, and by remnants of basaltic lava flows preserved in the adjacent Squamish valley. The Mount Cayley massif, the largest and most persistent volcano, is a deeply eroded stratovolcano comprising a lava dome complex made of dacite and minor rhyodacite ranging in age from 3.8 to 0.31 million years old. Mount Fee, a narrow volcanic plug made of rhyodacite about long and wide, rises above the highland ridge. Complete denudation of the central spine as well as the absence of till under lava flows from Mount Fee suggest a preglacial age. The other volcanoes of the central Garibaldi Belt, including Ember Ridge, Pali Dome, Cauldron Dome, Slag Hill, Mount Brew and Crucible Dome, were formed during subglacial eruptions to develop tuya-like forms with over-steepened, ice-contact margins. The primary volcanoes in the southern segment are Mount Garibaldi, Mount Price, and The Black Tusk. The oldest volcano, The Black Tusk, is the remnants of an extinct andesitic stratovolcano that formed during two distant stages of volcanic activity, the first between 1.1 and 1.3 million years ago and the second between 0.17 and 0.21 million years ago. Mount Garibaldi, a fairly dissected stratovolcano north of Vancouver, was built by Peléan eruptions between 0.26 and 0.22 million years ago during the waning stages of the last glacial, or Wisconsinian, period. Mount Price, a less significant stratovolcano just north of Mount Garibaldi, formed during three distinct periods of volcanic activity beginning at 1.2 million years ago and culminating with the eruption of Clinker Peak on its western flank 0.3 million years ago. In addition to the large, central andesite-dacite volcanoes, the southern portion of the Garibaldi Volcanic Belt includes remnants of basalt and basaltic andesite lava flows and pyroclastic rocks. These include valley -filling lava flows interbedded with till containing wood about 34,000 years old.