Complex sentence: Muir was one of the first to theorize that the major landforms in Yosemite were created by large alpine glaciers, bucking established scientists such as Josiah Whitney who regarded Muir as an amateur (see geology of the Yosemite area).
Split into simpler sentences: Muir was one of the first to theorize that the major landforms in Yosemite Valley were created by large alpine glaciers. This view contradicted established scientists such as Josiah Whitney who regarded Muir as an amateur (see geology of the Yosemite area).