In his first work, the monography Ertsforekomster i Søndhordland og Forekomster af Kise i visse Skifere i Norge from 1871, he claimed unconventional views which were not appreciated by elder colleagues.

His pioneering works on glacial erosion and the role of glaciers in the formation of valleys, fjords and lakes, from the mid-1870s, have later become classics.

[1] His views on glacial erosion opposed the mainstream theories of the time, but have later been adopted in the geological sciences.

He initiated the monumental work Norges Land og Folk, a book series published from 1885 until after his death.

[1] The mountain of Hellandfjellet at Prins Karls Forland, Svalbard, is named after him,[3] as is the Helland Glacier of South Georgia.