Wind erosion has also been considerable in Surtsey, especially erosion of the tephra during the first few years. At this time, a huge cloud of tephra dust could often be seen reaching far out to sea from the island. Winds have also eroded the palagonite tuff since its formation began. This erosion has not been accurately measured, but it has been estimated that 2-10 m have eroded off the tephra and palagonite tuff in various parts of the eastern crater.
On the sites where the islands Syrtlingur and Jólnir were once found, there are now only submarine hills. As was mentioned earlier, a peak called Surtla was also formed on the sea floor to the northeast of Surtsey. These submarine elevations have decreased in height at a steady rate due to erosion by sea currents. Syrtlingur disappeared in October 1965, and the present depth on that spot is about 34 m. Jólnir disappeared in October 1966, and the depth in that part of the ocean is now 39 m. On Surtla the shallowest spot was measured at 23 m in February 1964, but currently it is at least 47 m. These data on the marine erosion in Surtsey are very unique, as there are no comparable measurements from volcanic islands anywhere else in the world.
An effort has been made to predict the progression of marine erosion in Surtsey based on data on the island’s reduction in size over the years from 1967 to 2002. Theoretical models indicate that after 160 years only the core of the palagonite tuff will be left. Surtsey will then be surrounded by steep palagonite tuff cliffs that will slow down further erosion to a great extent. The palagonite tuff in Surtsey is very dense with few fissures, similar to the outer Vestmannaeyjar. In the future, Surtsey will most likely resemble the island Bjarnarey, which is approximately 5000-6000 years old.