Larsen was born in Astoria, Oregon to Danish immigrant Esper Signius Sr. and Louisa Pauly from Akron.

Later, Larsen returned to Berkeley and received a doctorate in 1918 with a thesis on the "Areal Geology of the Creede Mining District, Colorado."

In 1909 he joined US Geological Survey under Charles Whitman Cross, their studies on the volcanic San Juan Mountains was published in 1956.

[1] Larsen's major work was an analysis and tabulation of the optical characteristics of 600 minerals using liquid immersion within a hollowed prism.

After his retirement in 1949 he focussed on the development of the aging technique based on Lead, Uranium and Thorium ratios in zircon.