Research by Howel Williams superimposed the Crater Lake caldera on other Cascade stratovolcanoes including Mount Shasta in California and Mount Rainier in Washington state, and concluded that Mazama stood at pre-collapse, which has been accepted as the standard estimate by geologists. By the Holocene, the Mazama volcano was made up of several, clustered peaks with Mount Scott on the eastern end and Hillman Peak on the far west side. The volcanoes likely rose in elevation from east to west, and they also featured volcanic cones and lava domes on their southern flanks. Glacial horns like the Watchman lava flow were also present, and the mountain may or may not have sustained glaciers close to the summit. At the time of its collapse, Mount Mazama encompassed an area of and represented one of the major volcanoes in the High Cascades branch of the greater Cascade Range. It was the largest volcanic edifice between Mount Shasta in California and the Three Sisters complex in Oregon. Before the eruption, it had been significantly altered by glacial erosion, which carved U-shaped valleys on its southern and southeastern slopes. The northern and western sides of the caldera do not exhibit prominent evidence of glacial erosion, since they feature lava flows that only underwent alteration by late Pleistocene epoch glacial motion. Outside of the caldera, most hills show evidence of glacial alteration except those from the Holocene epoch and low elevation landforms including Pleistocene lava domes and cinder cones. Mount Scott has also been heavily eroded by ice, and the Union Peak volcano now consists only of a pyramidal horn.