Petrified forest

Lesbos contains one of the few known petrified forests and has been declared a Protected Natural Monument, included also in the European Geopark Network. Fossilised plants have been found in many localities on the western part of the island. The fossilised forest was formed during the Late Oligocene to Lower–Middle Miocene, by the intense volcanic activity in the area. Neogene volcanic rocks dominate the central and western part of the island, comprising andesites, dacites and rhyolites, ignimbrite, pyroclastics, tuffs, and volcanic ash. The products of the volcanic activity covered the vegetation of the area and the fossilization process took place during favourable conditions. The fossilized plants are silicified remnants of a sub-tropical forest that existed on the north-west part of the island 20-15 million years ago.

information:http://en.wikipedia.org/wiki/Lesbos