It emerged from the ocean as a result of active plate tectonics between December, 1965 and July, 1966.

Oceanic erosion cyclically wore down the new lava as it formed, and the island sank below the surface several times.

Jólnir's formation is closely linked to that of neighboring volcanic island, Surtsey, which emerged in 1963.

Volcanic eruptions occurred in much of the surrounding water, but newly formed land was subject to erosion and many small islands washed away.

The volcanic cone reached 64 metres (210 ft) above sea level,[1] but even this landmass eventually gave way to the eroding ocean waves.