Heart Peaks, originally known as the Heart Mountains, is a mountain massif in the Northern Interior of British Columbia, Canada. It is 90 km (56 mi) northwest of the small community of Telegraph Creek and just southwest of Callison Ranch. With a maximum elevation of 2,012 m (6,601 ft), it rises above the surrounding landscape on the Nahlin Plateau, which is part of the western Stikine Plateau. Heart Peaks has been an area of prospecting since the 1980s with the discovery of precious metals. Situated in a large area of volcanic activity, Heart Peaks consists of a large shield volcano. It was formed in the past 23 million years by repeated eruptions of lava and rock. However, present day eruptions have not been observed. A number of related volcanoes are adjacent to Heart Peaks and form an extensive volcanic zone over 1,000 km (620 mi) long. The knowledge of Heart Peaks is limited, especially its eruptive history.
Geology and geography
Setting Heart Peaks is part of the Northern Cordilleran Volcanic Province, a long volcanic chain extending from just north of the city of Prince Rupert in British Columbia through Yukon to the Alaska border. Along this line, the North American Plate has been rupturing. Earth's lithosphere consists of several large tectonic plates, which slowly move towards and away from one another, either converging and subducting or diverging and rifting; volcanoes and earthquakes are generated by these activities. The west coast of North America is the site of plate margins between the large Pacific and North American plates, and also between the smaller Juan de Fuca and Cocos plates. Tectonic activity along the North Coast of British Columbia and Southeast Alaska is characterized by transform movements of the Queen Charlotte Fault, a plate boundary where the Pacific Plate skids by the North American Plate. As the Pacific Plate moves northward to the Aleutian subduction zone, it generates rifting in the North American continent. Magma rises along cracks created by the rifting, and eventually erupts on the surface to form a volcano. This geological process has, over time, created the Northern Cordilleran Volcanic Province, which is the most volcanically active area in Canada. However, most of the volcanoes have not been directly dated or have not been dated in sufficient detail to recognize how active they are, making the prediction of volcanic events difficult and volcanic hazards uncertain.
Structure The nearly oval-shaped Heart Peaks shield volcano is made of basalt and trachybasalt with a composite thickness up to 430 m (1,410 ft); pyroclastic rocks are also present. It lies just west of the much larger Level Mountain shield and southwest of the Kawdy volcanoes. A series of steep-sided lava domes composed of porphyritic rhyolite and minor trachyte are situated on the western flank of Heart Peaks and display colours such as light green and pink. Rhyolitic lava domes are also present on its summit. The shield is surrounded by tributaries of the Inklin River, which flows northwest into the Taku River.
Heart Peaks is at least 33 km (21 mi) long and no more than 19 km (12 mi) wide at its base. The west and east flanks of the volcano are dissected, giving it a rugged appearance. However, its north flank is rounded and relatively smooth while its south flank is rather pointed. The highest elevation of Heart Peaks is 2,012 m (6,601 ft) at a small peak roughly in the middle of its summit plateau while the regional elevation of the Nahlin Plateau is 1,000 m (3,300 ft). This indicates that Heart Peaks has a topographic prominence of at least 1,012 m (3,320 ft). More than 20 unnamed creeks flow from the volcano, which drain into the nearby Dudidontu and Sheslay rivers. With an area of about 275 km2 (106 mi2) and a volume of less than 160 km3 (38 mi3), Heart Peaks is the third-largest volcano in the Northern Cordilleran Volcanic Province, exceeded by the Mount Edziza and Level Mountain shields, which cover more than 1,000 km2 (390 mi2). Heart Peaks is over five times larger than the Mount Meager massif in southwestern British Columbia, the largest stratovolcano by volume in the Garibaldi Volcanic Belt. The area surrounding Heart Peaks is largely undeveloped, with Callison Ranch being the only locality. Vegetation at the volcano is present mainly on its flanks as its broad summit consists of a rocky plateau. Because of its remote location, Heart Peaks is accessed by helicopter from the small communities of Atlin and Dease Lake.
Eruptive history
Background
Little is known about the eruptive history of Heart Peaks because it has not been studied in detail by scientists. The exact age of Heart Peaks is not known, but its first volcanic phase occurred during the Neogene period (between 23 and 2.5 million years ago). The variety of volcanic deposits at Heart Peaks indicates that it has a history of producing not only fluid and passive basaltic lava flows, but also more silica-rich trachyte and rhyolitic lavas and explosive eruptions. Phreatic breccias are found at the volcano, providing evidence that phreatic eruptions have occurred at least once throughout its eruptive history. Features created by subglacial eruptions are also present. The latest volcanic phase at Heart Peaks is largely Pleistocene (between 2.5 million and 10,000 years ago) in age and late-stage Holocene (10,000 years ago to present) activity is uncertain. This is partly because it is unknown whether Holocene volcanic rocks exist at the volcano. Nevertheless, the last eruption at Heart Peaks is unknown.
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