Lesvos terrain western islandThe island of Lesvos, Greece,  in the eastern Mediterranean Sea is located close to the coast of Turkey, and is the result of tectonic activity which has brought together Paleozoic basement and Cenozoic volcanics.  Volcanic activity, associated with the subduction of the African tectonic plate beneath the Anatolian plate, is responsible for most of the Neogene-aged deposits (21-16.2 Ma) that are exposed in the western side of the island.   The Northern Anatolian Trough fault, which is a right lateral transform fault, is the main fault, although there are many other synthetic and antithetic shear extensional structures found on the island.

 Sigri, Lesvos, from the bayThe Petrified Fossil Forest of Miocene age (18 Ma) is exposed in-and-around the town of Sigri, on the extreme western side of the island. It is a traditional coastal village and considered to be the most remote “tourist” destination on the island.  It boasts a small fishing harbor and a Turkish castle built in the 18th Century. The name of Sigri comes from the Latin word ‘securo‘ which means safe harbor.

Grocery Store

Typical of island life everywhere, small  mom- and-pop grocers supply each town or village with staples, while the agricultural and fishing industries provide everything else.  Although the selection of food items may appear to be limited, one always can see the influence of U.S. multinational conglomerates.  Witness the prominent display of CocoPuffs.

Natural History Museum, Sigri, LesvosThe Natural History Museum and the Lesvos Petrified Forest Geopark in Sigri is the jewel of the region, based around the Miocene-aged fossil forests now exposed across the region.  These organizations are a founding member of the European Geoparks Network.  The museum houses: an introduction to Earth History and plate tectonic activity in the region responsible for the island, today; exhibits on the petrified fossil forest including both specimens of permineralized trees, leaf impressions preserved in tephra (volcanic ash), and vertebrates; and an interactive room in which visitors can experience an earthquake.  The museum provides a condensed stratigraphy of the volcanic sediments, allowing visitors to the main park areas to identify the different deposits in the field.  These include tephra (volcanic ash fall), mudflow deposits (reworked tephra and silt-sized sediment), debris flows (pebble to boulder-sized rocks suspended in a mud matrix), and poorly developed paleosols (ancient soil horizons).

Tree 29 in Petrified Fossil ForestThere are six different areas within the boundaries of the GeoPark where fossil trees are exposed and can be viewed.  These include: (1) the “Kiria Apolithomeni,” or Main Fossil site, which has been known since the 18th century, and covers an area of 286 hectares; (2) the Sigri park in which well-developed root systems of numerous trees are uncovered, serving as proof that the plants were mineralized in situ (place of growth). The standing trees are either conifers or angiosperms and emerge from the layers of volcanic ash in which they buried; (3) the Plaka  park in which both impressions of leaves shed by the trees under ash fall and the largest diameter tree clump (> 14 m) are preserved; (4) the Nisiopi or Megalonisi islet which is found on the opposite side of the bay where both large conifers and more modest angiosperm coexisted in one or more forests;  (5) Hamandroula Park, in Eressos, exposes a large concentration of tree trunks lying flat or in growth position; and (6) the Skamiouda Park located near Antissa demonstrates not only the extensive area over which these forests thrived, but also the size of the trees attained in them.  Here, a a gigantic prostrate conifer trunk is found whose length is 15 m with a circumference of ~2m.  It is a representative of the sequoia ancestor Taxodioxylon gypsaceum.

TaxodioxylonThe most impressive tree in “Kiria Apolithomeni” is a giant sequoia-like conifer placed in the genus Taxodioxylon. It is preserved for a height of more than 7 meters (22.75 ft), has a circumference of 8.7 meters (28.3 ft), and its calculated height, when alive, is 102.2 meters (331 ft) tall!  This tree rivals the current redwoods now growing along the northern California coast.  But, the forest in which this tree lived is in the eastern Mediterranean.  The tree is rooted in a poorly developed paleosol (ancient soil) that shows very little evidence of soil-forming processes, and is buried first by volcanic tephra which is overlain by mud- and debris flows.  It is the largest tree in the “Kiria Apolithomeni” park, and was a canopy emergent in the Miocene forest.

Buried tree at PlakaThis tree, exposed in the Plaka Park, shows the effects of both the eruptive blast from the volcanic center, which is within 20 km of the site,  and the processes responsible for its subsequent burial and preservation.  This tree, like all standing trees in the Petrified Forest, is inclined rather than in a position perpendicular to the soil surface.  It’s tilting to the northwest is the result of the concussive blast that accompanied the eruption, pushing the tree in the direction of the eruption’s path.  The bottom 0.5 meters, or so, are buried in tephra (air fall ash) and thick intervals of boulder-and-cobble debris flows envelopes the tree.  The landscape subsequently was modified by another flow event that scoured down to a position just above the baseball cap (you can see the scour surface as a horizontal line).  The center of the now exposed tree rotted, as evidenced by its hollow nature, and filled with fine-grained tephra (the gray sediment seen within the middle of the upper tree).  This, too, was then covered in a debris flow deposit, entombing the tree for a second time.

Lesvos Boulder Debris Flow

The debris flow deposits range in thickness and composition across the area, both laterally and vertically.  This image is from the Nisiopi site across the bay where ocean wave-and-current activity has cut into the sediments, exposing their features.  The bottom of this section is a boulder conglomerate debris flow in which volcaniclastic rocks of varying composition occur.  The largest boulder in this image is >1 meter across.  The upper surface of the boulder conglomerate debris flow is eroded (the uneven contact in the image) and overlain by a cobble to granule (2-4 mm) conglomerate in which you can see crude bedding structures.  Atop this debris flow is another boulder conglomerate debris flow.

SunsetThe sunset over the Mediterranean Sea hasn’t changed much in the past 20 million years.  But, the landscape and ecosystems on these ancient landscapes have changed considerably.  When eruptions from the Vatoussa crater occurred, trees the size of modern redwood Sequoia’s grew on the island as emergents above a canopy of other conifers (pines) and angiosperms (flowering plants). Today, the landscape is dominated by shrubs on the western side and trees on the eastern side of the island, with an estimated 1400-1500 plant taxa. This richness is  due to the variety of biotopes found on the island, the array of rock types and their distribution, the long-term effect of man’s activity on nature, the island’s close proximity to Asia Minor and its recent, geologically speaking, detachment of the East Aegean from the coasts of Minor Asia.