The problem:

I want to have a volcanic island with an everlasting lava outflow completely overgrown by (jungle) plants. It therefore follows that plants should also grow above the lava.

I know that volcanic ash is very fertile, so the plants can grow well.

However, I see the heat of the lava as a problem: if the lava is completely overgrown, the heat accumulates and thus burns the plants. As a solution to this, I have thought of "natural" chimneys, mostly vertical open spaces that remain free of growth and give the heat an escape.

I can make a fertilizer and other things with handwavium, however I don't want to change the plants.

Can plants with infinite good conditions grow over lava and cover it completely ?

And what things do I need to do this ?

The world:

Wealthy scientist Alice would like to work quietly on the solution to end world hunger. However, she is constantly distracted by people: the UN keeps asking about progress, the press for unnecessary interviews, her wife when she would be coming home. All these unimportant things keep her from doing her research.

However, recently the evil scientist Bob was defeated by the World-Police™ and his lair of evil, a cozy volcanic island somewhere in the middle of nowhere, is for sale. With its own trench full of lava that drains into the sea and a basement full of stuff made with handwavium. And thanks to the never ending lava flow, the island is also getting bigger and bigger, you get more and more land. So strike today and buy it.

Alice strikes, buys the island, disappears from the world stage and calmly develops a super fertilizer. With its own field test on the island.

After testing and documenting everything, she gets hit by a flowerpot that fell off the shelf and dies. The flower pot was red and had a smiley face on the side. It was a good flower pot. We will miss you, Charlie, the flower pot.

200 years later, everything is overgrown with plants, the original island is no longer recognizable, and Charlie is still dead. In this initial state, the island is rediscovered....

  • 1
    $\begingroup$ Not sure if it fully satisfies your need but some plants can grow on solidified lava (not just volcanic ash) given the conditions (I believe it requires a rainy region at least). Here are some related sources: 1 , 2 , 3 $\endgroup$
    – ermanen
    Commented Apr 28, 2022 at 18:23

2 Answers 2


Lava tubes:

Most likely, the perpetual river of lava will move and shift over time, since the fluid turns to rock if it sits for even a short time. It would keep burning a new path. The lave dams itself, backs up, flows in a new direction, or fans out. Lava is very viscous and doesn’t flow like a classical river.

If the lava DOES perpetually flow in the same channel, it will likely eventually cool unevenly and form a lava tube. Lava flows have left lava tubes all over the globe. A ceiling of solid rock forms and ash/plants can be growing directly over the lava flows. As long as there is enough insulation so the plants don’t cook, they’re fine.

This also has the lovely fun of the ground giving away to a hidden river of molten rock…


I think you are facing an though problem:

  • flowing lava is hot, and that heat keeps water away. As long as there is no water, no seed can sprout. Even with a torrential rain supplying water, a plant would need time to grow. That time plus the rain would not make the lava flowing any more.
  • growing plant need some soil, not rock. Again, soil formation takes time and weathering.

The only way around seems to be to cover the flowing lava with a somewhat thick layer of soil (either artificially or by some avalanche) and have plants grow in that soil, while the lava keeps happily flowing beneath it. If the climate is cold, a warmed soil can actually help plant growth.


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