The power of natural hazards only comes to our mind when one is reported in the news. Often, we hear about it for a few days and the magnitude and extent of the event is quickly forgotten, until the next disaster strikes. The geologic record holds these events in a stratigraphic booklet, imprinted in the layers of rock found at Earth's surface. And, nowhere else on Earth is there a better record of the magnitude of volcanic activity and its consequences than on the island of Lesvos. It must be seen to be understood.
The Natural History Museum in Sigri is the starting point to learn about how different the landscape of the island was some 20 million years ago. The museum provides an excellent introduction to the geology of the island, the consequences of the multiple volcanic eruptions that built this part of Lesvos, and a fundamental understanding of the role plate tectonics plays in the Aegean. The museum design is beautiful, the displays organized well, and the staff helpful and friendly. But, it is not just the museum that needs to be visited, but the fossil forests, themselves, exposed in 3 (soon to be 4) sites in the area.
The Sigri exposure, some 5-6 km from the museum, shows what are the consequences of recurrent volcanic eruptions from a volcanic complex some 10-15 km to the east. Here, you can see at least 10, superimposed and stacked fossil forests in which many of the trees were buried upright in growth position. These forests were not composed of small trees. Rather, the trees at several horizons are comparable in size to the Giant Redwood forests of California. Each forest, which probably grew for a millennium or more, was buried either in volcanic dust falling from the atmosphere (tephra) or in massive mudflows or debris flows that accompanied volcanic activity on the island. The tallest tree buried in one of these deposits is 7 m (23 ft) tall, and the largest tree, found in the Paka park, has a circumference of 14.5 m (48 ft)! There is a mix of both flowering plant trees (angiosperms) and conifers (cupressaceae), and each is preserved by silica in a process known as permineralization. The colors of these trees are exquisite in addition to cellular preservation that has allowed for them to be identified.
It is well worth a day trip from Mytilini to Sigri to visit the museum and natural parks. If you do, you must remember in the back of your mind that all the rocks and landscape you witness for the entire part of the western island, and into the Mediterranean and beyond), all formed as a consequence of volcanic activity. The scale and magnitude of these eruptions is mind boggling.
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