The Miles Canyon Basalts represent a package of rocks that include various exposures of

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

ic lava flows and cones that erupted and flowed across an ancient pre-glacial landscape in south-central

Yukon Yukon () is a Provinces and territories of Canada, territory of Canada, bordering British Columbia to the south, the Northwest Territories to the east, the Beaufort Sea to the north, and the U.S. state of Alaska to the west. It is Canada’s we ...

. The

volcanic rock Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and me ...

s are best exposed and most easily accessible at the Miles Canyon location where the

Yukon River The Yukon River is a major watercourse of northwestern North America. From its source in British Columbia, it flows through Canada's territory of Yukon (itself named after the river). The lower half of the river continues westward through the U.S ...

cuts through a succession of flows south of

Whitehorse Whitehorse () is the capital of Yukon, and the largest city in Northern Canada. It was incorporated in 1950 and is located at kilometre 1426 (Historic Mile 918) on the Alaska Highway in southern Yukon. Whitehorse's downtown and Riverdale areas ...

. In the spring, good exposures can also be seen immediately downstream from the Yukon River hydro dam in Whitehorse which was built to extract energy from the cataracts that were the

White Horse Rapids The Whitehorse rapids were rapids on the Yukon River in Canada's Yukon Territory, named for their supposed resemblance to the mane of a charging white horse. The rapids formed where the Yukon River flows across and cuts down through lava flows of ...

. These rapids and the Miles Canyon provided a significant challenge to

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

-seekers heading to the Klondike Gold Rush, and also established the upstream terminus for paddle-wheel river boats. Thus, the Miles Canyon Basalts are the reason for the establishment of the townsite of Closeleigh, eventually the City of Whitehorse. The

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

s and cinder cones in the Alligator Lake volcanic complex southwest of Whitehorse are the greatest accumulation of these rocks. The Miles Canyon Basalts were thought to be

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

age. However, geological investigations supported by geochronological analyses indicate that these rocks are much older. The 'type' Miles Canyon flows along the Yukon River are ~8.4 million years old (

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

) and the Alligator Lake flows are ~3.2 million years old (

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Volcanism in Canada Volcanism, Volcanic activity is a major part of the geology of Canada and is characterized by many types of volcanic landform, including lava flows, volcanic plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcan ...

List of volcanoes in Canada List of volcanoes in Canada is an incomplete list of volcanoes found in Geography of Canada, mainland Canada, in the Islands of Canada, Canadian islands and in Canadian waters. All but two Provinces of Canada, provinces, Prince Edward Island and ...

References

* *Pearson, F.K., Hart, C.J.R., Powers, M., Distribution of Miles Canyon basalt in the Whitehorse area and implications for groundwater resources. In: Yukon Exploration and Geology 2000, D.S. Emond and L.H. Weston (eds.), Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 235-245. http://emrlibrary.gov.yk.ca/ygs/yeg/2000/2000_p235-246.pdf *Hart, C.J.R., and Villeneuve, M. 1999. Geochronology of Neogene alkaline volcanic rocks (Miles Canyon basalt), southern Yukon Territory, Canada: the relative effectiveness of laser 40Ar/39Ar and K-Ar geochronology. Canadian Journal of Earth Sciences, v. 36, p. 1495-1507, 10.1139/e99-049 http://www.nrcresearchpress.com/doi/abs/10.1139/e99-049#.VASMHkDCdYA Volcanoes of Yukon Northern Cordilleran Volcanic Province Pliocene volcanism Miocene volcanism Neogene Yukon Lava flows {{Yukon-geo-stub