Ilgachuz ranges, the Itcha Range is composed of small coalescing volcanic units rather than a stratiform volcanic pile. It is, in many respects, similar to the small alkaline shields found in Kenya and Ethiopia along the East African Rift. About 60% of the shield is exposed while roughly 40% of it remains buried under glacial drift deposits. This suggests that the Itcha Range was glaciated repeatedly during the Pleistocene epoch. Glacial striae on polished surfaces of some of the oldest volcanic rocks in the eastern part of the shield and the local presence of drift deposits throughout the stratigraphy indicate that glaciation and volcanism were contemporaneous through much of the volcanic history of the Itcha Range. With a maximum elevation of , the Itcha Range is the lowest of the three Anahim shield volcanoes. Its highest point is Mount Downton, which is situated in the middle of the shield. Just to the northeast is Itcha Mountain, the second highest peak with an elevation of . These peaks are situated on top of the shield, which has a topographic prominence of about . The Itcha Range has a broad, gently sloping structure typical of shield volcanoes. It is mainly composed of thick felsic lava flows that were erupted from a central vent. These are overlain by thick mafic alkaline lava flows and at least 30 small cinder cones. Hawaiite is the dominant rock type, but alkali olivine basalt and spinel lherzolite-bearing basanite is also present. They merge laterally with lavas of the much older Chilcotin Group, which surrounds the Anahim Volcanic Belt. However, the exact nature of the relationship between the Anahim Volcanic Belt and the Chilcotin Group is unknown. Exposed in the middle of the mountain range is an assemblage of deformed andesite to dacite lava flows and volcanoclastic sediments. These basement rocks were created during the late Mesozoic era, long before the Itcha Range formed. They are similar to rocks found in the Hazelton Group, situated north of the Itcha Range, and the Ootsa Lake Group of the Intermontane Belt. Volcanic history Two stages of volcanic activity constructed the Itcha Range. The first stage, referred to as the felsic shield-building stage, occurred between 3.8 and 3.0 million years ago. Three phases comprise this stage; a pre-explosive phase, an explosive phase and a post-explosive phase. Analysis of the first trachyte magmas to erupt during the pre-explosive phase suggest they were