Muir developed his theory that Yosemite Valley was carved by glaciers, challenging the prevailing view that it was formed by a cataclysmic event. He gathered extensive evidence to support his claim, studying glacial features and landforms.

Muir published his initial findings on the glacial formation of Yosemite in scientific journals, sparking debate among geologists. His ideas were initially met with skepticism but gradually gained acceptance.

Muir conducted extensive studies of glaciers in Alaska, further solidifying his understanding of glacial processes and their impact on landscapes. He documented the movement and behavior of glaciers, contributing valuable data to the field of glaciology.

Muir consistently emphasized the importance of understanding geological processes in his writings and advocacy. He believed that a deep understanding of nature's forces was essential for appreciating and protecting the environment.