Grænavatn
About Grænavatn
Grænavatn is a small crater lake in Krýsuvík whose water turns a milky green that looks almost painted on. It fills an explosion crater right beside Route 42 on the Reykjanes Peninsula, so you can see it from the car and walk to the rim in a minute.
Geologists describe it as a pair of maar craters, blasted open when rising magma met groundwater, probably more than 6,000 years ago. The lake is more than 40 meters deep. The color comes from thermal algae and minerals in the water, and it reads strongest on a bright day with the sun high.
Grænavatn sits about 45 minutes from Reykjavík by way of Hafnarfjörður and Route 42, past the lake Kleifarvatn. The Seltún geothermal area is only a couple of kilometers north on the same road, which makes the two an easy pairing. Park at the roadside pullout by the crater and give yourself 15 to 20 minutes to walk part of the rim.
The crater edges are loose gravel, and wind across Krýsuvík can be strong. Check road.is in winter and safetravel.is for any eruption-related closures on the peninsula.
Good to know
Why is Grænavatn green?
Its color comes from thermal algae and minerals suspended in the water. The green looks brightest on sunny days.
How was Grænavatn formed?
It fills two maar craters made by steam explosions when magma met groundwater, probably more than 6,000 years ago.
Is Grænavatn accessible by car?
Yes. The crater lake sits right beside Route 42 in Krýsuvík, with a pullout a short walk from the rim. A regular car is fine in summer.
How far is Grænavatn from Seltún?
Only a couple of kilometers. Drive south from Seltún on Route 42 and the lake appears on the side of the road within a few minutes.
How deep is Grænavatn?
Published figures put it at about 45 to 46 meters, which is deep for such a small crater.
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