Lóndrangar are a pair of sharp and steep cliffs, or volcanic plugs of basalt, that have been hewn out from softer surrounding rock by erosion. At 75 m and 61 m respectively, they are quite a sight.
Lóndrangar are volcanic plugs left out as remnants from a bigger crater, which has since mostly eroded away with time.
And what is a volcanic plug, and how does it form?
Also called a volcanic neck or lava neck, it is created when magma hardens within a vent on an active volcano.
When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it. This can sometimes lead to an explosive eruption. But if a plug is preserved, erosion may remove the surrounding softer rock while the erosion-resistant plug remains, producing a distinctive upstanding landform.