Around Faxafói bay SW-Iceland land is subsiding. This can be verified both in place names, in the geology as well as in direct measurements. The name Seltjarnarnes means a peninsula with a lake and seals.
The Seltjörn lake is believed to have existed as a fresh water body or slightly brackish until the beginning of the 18. century but then it was changed in to an inlet at the seashore because of combined effects of subsidence and sea erosion.
During spring tide ebb unique remnants of peat layers appear in the tide water zone. This submerged peat was formed in a marchland, grown with sedge and willow. The peat can be seen both in Seltjörn and in the nearby Bakkavík at the south coast of the peninsula. The peat is 3000-10.700 years old and indicates that the peninsula has subsided 3-5 m during the last 3000 years and 1-1,5 m from the times of settlement. Submerged peat is known in several places in Faxaflói such as at Kjalarnes and Garðskagi.
The submerged peat and the littoral zone of Seltjörn can be observed by walking from the parking place near Bakkatjörn to the seashore during spring tide ebb. During neap tide the peat does not appear.
Árni Hjartarson, 2010.