[1][2][3] Nummedal was educated as a geologist, and in 1909 he was employed as a teacher at Kristiansund High School (Norwegian: Kristiansund høyere almenskole) when he found traces of people living on the Norwegian coast approximately 8,000 years ago.

Nummedal found these settlements from the Fosna culture while he was studying the shorelines and post-glacial rebound during the time after the last ice age.

[1] The first discovery was made at Lake Voll (Vollvatnet) on the island of Nordlandet in Kristiansund.

Nummedal was named a government scholar in 1917, and he was associated with the University Collection of Antiquities in Oslo as a conservator.

[1][6][7] Nummedal was a member of the Norwegian Academy of Science and Letters, and in 1936 he was named a knight first class of the Order of St.