 Starting in 1797, Esmark was employed as a lecturer in mineralogy at the Kongsberg Mining Academy.In 1814, Esmark became Norway's first professor of geology as a professor of geology at the University of Oslo, and was described as "a pioneer in glacial geology", by professor of Quaternary geology and Glaciology Bjørn G. Andersen.In August 1801 Esmark was the first person to ascend Snøhetta, highest in the mountain range Dovrefjell in southern Norway.