"The Þingvellir area is a part of the North Atlantic rift system, almost entirely nested within the Reykjaneshryggur-Langjökull rift system. It can be described as an area of sea-floor spreading, displaying the close association of crustal rifting and volcanism. Þingvellir and the Great Rift Valley of Eastern Africa are the only sites on Earth where the effects of two major plates drifting apart can be observed."

Geology and Tectonics of Þingvellir