Choquette Hot Springs Provincial Park in northwestern British Columbia. Xenoliths, rock fragments that become enveloped in a larger igneous rock, are widespread in the Northern Cordilleran Volcanic Province. Xenoliths that originated in the Earth's crust include rich metamorphic rocks and felsic intrusive rocks. Granulite xenoliths exist mainly at the Fort Selkirk Volcanic Field in central Yukon, Prindle Volcano in easternmost Alaska and at Castle Rock and the Iskut River in northern British Columbia. Felsic intrusive xenoliths are a lot more common and usually originate from adjacent granitic intrusions, including those that form the Coast Mountains. More than 14 volcanic zones throughout the Northern Cordilleran Volcanic Province comprise xenoliths that originated from the Earth's mantle and are located mainly at the Yukon–Tanana Terrane, the Cache Creek Terrane and at volcanoes occupying the Paleozoic and Mesozoic Stikinia terrane. They consist of lherzolite, harzburgite, wehrlite, dunite, websterite and garnet composed pyroxenite. The highest and lowest temperatures recorded by mantle xenoliths increase to the south and decrease to the north. Mantle xenoliths at Prindle Volcano in easternmost Alaska record the minimum temperature of and mantle xenoliths from the Fort Selkirk Volcanic Field in central Yukon record the minimum temperature range from . At Castle Rock in northern British Columbia, mantle xenoliths record the maximum temperature of , as well as the maximum temperature range from . The minimum xenolith temperatures indicate that the boundary between the Earth's crust and mantle is shallowest beneath the northern portion of the Northern Cordilleran Volcanic Province. Therefore, the temperature ranges for the northernmost xenolith series is about one-half the temperature range found in xenoliths at the southern portion of the volcanic province. Megacrysts, crystals or grains that are considerably larger than the encircling matrix, are commonly found in lava flows throughout the Northern Cordilleran Volcanic Province. They consist of three different groups, including kaersutitic amphibole megacrysts, clinopyroxene megacrysts and plagioclase megacrysts. Megacrysts made of kaersutite are known to be found mainly at Llangorse Mountain in northern British Columbia. Black glassy clinopyroxene megacrysts are widespread throughout the Northern Cordilleran Volcanic Province, suggesting their creation is independent of lithosphere structure. In contrast, clear glassy plagioclase megacrysts are found largely at the southern end of the Northern Cordilleran Volcanic Province and largely within the boundaries of the Stikinia terrane. This suggests the plagioclase megacrysts have a source that is sensitive to the Earth's lithosphere, including contamination or magma ponding. Megacrysts made