Ice age

The theory of the Ice Age proposed that extensive ice sheets had once covered vast mountainous and lowland areas and this concept was pivotal in advancing the understanding of Earth's climatic and geological history. It was a crucial development in geology and paleoclimatology.
 Not mentioned explicitly but associated with Louis Agassiz Switzerland 1837 Ice age

The theory of the Ice Age proposed that extensive ice sheets had once covered vast mountainous and lowland areas and this concept was pivotal in advancing the understanding of Earth's climatic and geological history. It was a crucial development in geology and paleoclimatology.