Icelandic Geothermal Bread

Image credit: Laugarvatn Fontana

Geothermal Lava Baked Icelandic Rye Bread

This post is part of our Something Different series.  A series aimed at spreading awareness for unique and offbeat cultural practices.  Become a citizen of the world.

Icelandic rye bread, also known as rugbrauð, is baked underground in Iceland using Geothermal energy.  Yes, you heard that correctly.  The magma and lava beneath the earth is possibly the coolest way to cook Icelandic bread.  It’s also sometimes known as Thunder Bread or Icelandic Lava Bread.

This stuff though…  is so far the best bread I’ve ever tasted.  It can take upwards of 12 hours to cook, and tends to be on the doughy, moist and sweet side.  Serve with Icelandic butter.

Geothermal Icelandic Rye Bread, Thunder Bread or Iceland Lava Bread Recipe - Aka Rúgbrauð

Image courtesy

The method is simple.  Allow ingredients within a covered and sealed pot to sink into the Earth near a geothermal hot spot.  Steam then cooks the bread.  Of course you don’t need to travel to Iceland to experience Rugbrauð.  Many famous cafes in downtown Reykjavik cook their bread on low heat in the oven overnight.  Though they can afford to do so; thanks to the abundance of cost-effective geothermal power provided by the vulcanized Earth within Iceland.  Over 60% of Iceland’s power is derived from geothermal sources.  You can scroll down for both the Icelandic geothermal bread recipe, as well as the easiest method to cook this unique item in your own kitchen.

Icelandic Rye Bread Recipe and Ingredients

Image credit: Laugarvatn Fontana

So why Rye?

Rye is particularly easy to grow, and though its yields are lower than wheat in good soil, it can survive harsher climates in mediocre soil.  Also, if it matters to you, rye bread has little to no gluten.

Icelandic Rye Bread Recipe and Ingredients

2 Loaves

  • 2 1/2 cups rye or dark rye flour
  • 1 1/2 cups whole wheat flour
  • 1 large Tbsp. baking powder
  • 1 tsp. Hawaiian Black Lava Salt (or just salt)
  • 2 cups buttermilk
  • 1 1/2 Tbsp. molasses
  • 1/2 cup brown sugar
  • 1 cup hot water

Method for Baking Icelandic Geothermal Rye Bread (Thunder Bread)

  1. Preheat oven to exactly 200 degrees Fahrenheit
  2. Coat your baking pan with a thin layer of unsalted butter or brush with avocado oil
  3. Whisk ingredients mentioned above with either a hand or mechanized whisker
  4. Add and stir molasses, buttermilk and brown sugar until fluid and silky
  5. Cover with aluminum foil and form an air-tight seal as best you can to preserve moisture
  6. Bake for 6-8 hours or until cooked uniformly through

Watch Icelandic Rye Bread (rugbrauð) Get Baked Underground



  • That is great. Thanks for the recipe although I do not have a clue how I will make it in Louisville, KY. Where did you get the idea to use Hawaiian lava salt? That made me laugh because Hawaii and Iceland are, literally, worlds away.

    • @Scott,

      Because they don’t yet sell Icelandic lava salt ;). I figured if you’re going to make geothermal bread, might as well use real parts of SOME volcano. And you can certainly cook it in Kentucky. Just cook it for 10-12 hours in your oven around 200 degrees.

  • Liz D

    Loved the dark rye bread we had everyday with breakfast in Iceland, so I was very excited to find this recipe. Used the ingredients called for. Covered the pans tightly with aluminum foil, and baked in a 200 degree oven with a bowl of water for 6 hours. The texture and color were right, very moist, but it was really, really, salty. I suspect the recipe above should call for baking powder instead of baking soda. Or if you use baking soda, omit the salt.

  • Mike

    I had “lava” bread about 20 years ago in Iceland, and have been looking for a recipe. I tried this but had some problems. When I read “stir until fluid and silky” I was expecting perhaps a stiff batter. I could not stir it at all after awhile, I had to try to knead it in the large bowl, and finally knead on a breadboard. It took several minutes of kneading just to incorporate all the dry mixture. I divided it in two, and formed a couple of loaves which I then pressed into the pans. I wrapped the pans completely in a couple of layers of foil to make it almost air tight and baked for 6 hours. The final product tastes good, but is so dry that it really needs a copious layer of butter.

    I tried to be very careful with the directions, and don’t think I used more flour than listed. Should the dough require kneading?


  • isabelle

    Hi … and is there a place in Iceland where we can have a cooking experience with an icelandic person ? / or see in realtime how it is made ? many thanks 🙂

  • Mary

    How large a pan do you use to bake the bread? Looks wonderful! Can’t wait to try and bake the bread .

  • Pamela

    I would disagree on the baking soda v. powder. You NEED the soda with the buttermilk acid. 1 Tbsp, leveled is no more than you use in Irish soda bread. If you do use more though you will taste the “soda” not the salt.

Leave a Reply

Your email address will not be published. Required fields are marked *