A long time a volcano erupted in Iceland. This volcano spewed out basalt lava field (Hawaii style). This lava did flow over a forest that was nearby and killing all the trees in it. Few weeks ago and several million years later and few kilometres down the remains of this forest was found. Since one of the tree did fossilize in the lava. As the tree was engulfed in the lava it did turn to charcoal that was later removed by water and leaving the empty imprint of the tree in the bedrock.
The remains of the tree are now clearly visible in the road construction tunnel. The hole after the tree is full of water and part of it has been removed by the tunnel digging. Picture of it along with news can be found in the link below.
Fossil of a tree found in tunnel construction
Far eftir trjábol í Vaðlaheiðargöngum (Rúv.is, Icelandic, Picture)