Bluff on the eastern flank. Gandalf Ridge is a promontory formed by northward-tilted debris and penetrated by Dikes. It is located at the foot of Hurricane Ridge, and Pinnacle Valley is located on the Riviera Ridge. Dikes, lava domes, lava flows and pyroclastic deposits are found in outcrops. Mason Spur also contains breccias from pillow lavas, while Gandalf Ridge features a diamictite and a cross-cutting fault. Mason Spurr was considered by Martin et al. 2021 to be a separate volcano from Mount Morning. Owing to the lack of running water, the main edifice (unlike Mason Spur) is uneroded and parasitic vents have a young appearance. Glacial erosion has eroded some parts of the volcano, leaving volcanic necks in Pinnacle Valley, has etched glacial striations into exposed volcanic rocks and deposited glacial till. The Vereyken Glacier descends the northeastern slopes of Mount Morning between Hurricane Ridge and Riviera Ridge. Moraines occur on these two ridges and moraines dating to the Wisconsin glaciation have been reported. Glaciers descending from Mount Morning feed the Koettlitz Glacier. Several lakes are found on the volcano and at its foot, including Lake Morning at the end of the Riviera Ridge and Lake Discovery at the foot of the Hurricane and Gandalf ridges. Geology The West Antarctic Rift is a major geological feature in Antarctica and one of Earth's largest continental rifts. It is a region of active crustal extension and spreading, which may be ongoing today. Volcanic activity occurs at the rift and includes the McMurdo Volcanic Group, a long chain of volcanoes in Victoria Land. This volcanic group has erupted alkaline lavas during the course of the Cenozoic. It is subdivided into three provinces, the Hallett, the Melbourne and the Erebus province; Mount Morning is the southernmost volcano of the Erebus province. Mount Morning rises from a Paleozoic basement, the Koettlitz Group which crops out close to Gandalf Ridge in the form of granite and metasedimentary rocks. Based on rocks erupted by Mount Morning, the crust appears to be thin and has a calc-alkaline composition. Tectonic sutures in this basement may have allowed magma to ascend to the surface in the Mount Morning region. Composition Basanite is the dominant rock of outcrops, with phonolite less common and picrobasalt and tephrite rare. Outcrops of older rocks include mugearite, rhyolite and trachyte. Textures range from porphyritic to seriate. Various phenocrysts are found within the volcanic rocks, including