Kerid is a caldera 55m deep and 270m across and the crater is located in the Grímsnes area and a part of Iceland´s western volcanic zone and right next to highway 35 going towards Gullfoss and Geysir, and close to where highway 36 leads up to Thingvellir National Park. The bottom of the crater has a lake which follows the ground water table and has a striking opaque color caused by the minerals in the soil. The volcanic rock in the Kerid crater has a striking red color which is relatively common in this area but much less out the Reykjanes Peninsula for example where black is the most common color.
For a long time the theory among volcanologists was that the Kerid was formed during an explosion and would therefore qualify as pseudo crater. However, further study showed no signs of such a massive explosion and it is now believed that Kerid was formed when cone volcano had emptied its magma reserve chamber during an eruption and then fell in on itself from its own weight creating the volcanic crater lake.
The south of Iceland is basically a system of volcanoes and the theory is that there is a piece of the tectonic plate loose here. Just off the coastline are Vestmannaeyjar islands which were created in a series of massive eruptions about 5,000 years ago, and suffered two eruptions in the 20th century. The first one was the great Surtsey eruption that lasted from 1963 until 1967 a created a new island at the southern tip of the archipelago. The second one was the Heimaey eruption which started in January 1973 and is the only recorded case of a volcanic eruption starting on the outskirts of a town in Iceland. Eyjafjallajökull the infamous volcano that erupted in 2010 and made world headlines is just a little further to the north on the mainland, and a little further north from there is Mount Hekla which is one of the most active volcanoes in Iceland. To the east is the massive Mount Katla which last erupted in 1918 and then as it has before changed the coastline bringing out so much ash and gravel that it was pushed out around 200 meters.
Kerid is only about 15 km north of Selfoss village which is right on the crossroads between where the Golden Circle and the South Shore tours both start effectively. Any time of year is a good time to visit Kerid and in fact every season offers a slightly different look. Whether it is summer or winter, midnight sun or northern lights, this is a good stop. Be aware that there is a small entrance fee charged by the landowners.