I saw this rock formation near Hveravellir, Iceland. It is probably of volcanic origin and looks like a dome. It is nearly symmetric and appears to consist of hardened lava maybe, with several very big cracks that divide it into sections. It is quite far away from the lava flows of the old, very flat Strytur volcano that is about 2 km away.

I have several hypotheses of my own, but I am not a geologist. Could it be a small "failed volcano"?

enter image description here

  • $\begingroup$ Can you see what's inside? $\endgroup$ – Gimelist Sep 2 '14 at 9:37
  • $\begingroup$ Could this be an extinct fumarole? $\endgroup$ – user889 Mar 28 '15 at 9:23
  • $\begingroup$ It is in the area of thermal springs and gas vents, so may potentially be. $\endgroup$ – h22 Mar 28 '15 at 16:04

The vast majority of magma never even makes it out to the surface - most is simply crystallised at depth in magma chambers which dead-end several kilometres below the surface, or are injected as dykes or sills within the host strata.

By OrbitalPete, posted on reddit.com

If magma rose up below that mound it probably got closer than several kilometres to the surface; and the theory could be tested with one drill hole. I'm assuming the mound itself is not lava as such but bedrock that's been forced up.

  • $\begingroup$ How "forced up"? Why the land around has not been forced up? It is not very big, somewhat 20 meters in diameter at most. $\endgroup$ – h22 Sep 3 '14 at 8:06
  • 2
    $\begingroup$ Without drilling this is all guesswork but there could be a crystallized plume which is only that size. $\endgroup$ – mistermarko Sep 3 '14 at 9:17
  • $\begingroup$ Read up on it - the best way to investigate this may be using reflection seismology. It could produce a 3d map of differences in the rock below the surface. $\endgroup$ – mistermarko Sep 4 '14 at 0:35

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