Mediterranean_Geology

IMPORTANT NOTICE: All photos are copyrighted by Raymond Wiggers. If you are an educator or student and would to like to use any of these images, e-mail me and let me know how the images will be used. Please also credit me as the photographer. I ask that all companies, organizations, and government agencies contact me about my fees for the use of my photos, and about obtaining higher-quality versions on CD-ROM. Thanks for your understanding and compliance with the law.

To go directly to a particular nation represented in this gallery, click on its name below:

- Egypt

- France

- Greece

- Israel

- Italy

- Spain

- Tunisia

3. A section of the breathtaking Daluis Gorge of the Var River, in Haute Provence -- the French Maritime Alps north of Nice. Note the vegetation that clings to the steep canyon walls. This would not be the place to hunt for plants that set new records for longevity. The small volume of water passing through the canyon in this photo gives little indication of the erosive power of this river during its spring floods. Most streams do the vast majority of their erosional work during just a few days or weeks each year.

4. Even in summer, though, when the streams in the upper stretches of the Var Valley are reduced to almost a trickle, what water there is carries a large load of suspended fine sediments eroded from the region's soils and rock out-crops.

12. The Corinth Canal, completed in 1893, connects the Aegean and Ionian Seas; ships can here avoid circum-navigating the Peloponnesus. (I can state from personal experience that sailing around the southern tip of Greece in winter can be a surprisingly stormy proposition.) About four miles long and almost 260 feet deep, the steep-walled canal is cut into Pliocene- and Pleistocene-Epoch marine-terrace deposits: marl, sandstone, conglomerate, limestone, and unconsolidated sediments.

16. An asymmetrical fold in sedimentary strata along the main road from Jerusalem to the Dead Sea. Such struc-tures suggest a history of crustal disturbance and deformation -- which is certainly no surprise in this geologically active part of the world.

17. At about 1,200 feet below sea level. This is the western escarpment of the Dead Sea Graben, a northern extension of the saltwater-flooded Red Sea Rift. As mentioned in the text to Photo 14, above, a graben is a troughlike, dropped block of the earth's crust surrounded by normal faults. One of these faults runs along the base ofthis cliff. In geo-jargon, this is a unexcelled example of "extensional tectonics." In plain English, it's a place where the Earth's crust is pulling apart. To be specific, the Arabian plate on the east is pulling away from the African plate on the west.

19. Lago Albano, a lake in a volcanic cone southeast of Rome. This scenic spot is just one part of a larger volcanic structure known as the Colli Albani -- the Alban Hills. The Lago Albano cone, and the smaller Lago di Nemi cone nearby, were produced by eruptions in the late Pleistocene Epoch, over 20,000 years ago.

20. The Auruncian Mountains in winter, as seen from the Gulf of Gaeta, on Italy's western, Tyrrhenian Sea coast. There are volcanoes to the north and south of this range, but it is decidedly nonvolcanic, and composed of limestone that originated as part of a carbonate platform in a shallow saltwater sea. The knoblike peak visible just left of center on the enlarged version of this photo is Il Redentore.

21. Looking in the opposite direction, from high in the Auruncian Mountains toward the seaport of Gaeta. At right is the summit of Il Redentore; at left, in the distance, is Gaeta's old quarter and Monte Orlando. The latter, once a limestone island, is now connected to the mainland by a narrow strip of beach. Geologists call this type of landform a tombolo.

23. Back in the late 1970s, I was an officer in the U.S. Navy, stationed on a ship homeported in Gaeta. I chose to live ashore in Spigno Saturnia, a small agricultural community up in the southern reaches of the Auruncian Mountains. Thanks to the limestone bedrock and other factors, this locale was a karst (cavern and sinkhole) terrain. Beneath my house ran a cave complex of unknown extent. Here, in one explored section, I came across many interesting speleothems (structures formed by calcite precipitating out of dripping or flowing water). This form, resembling a cauliflower turned upside down, is a flowstone. Its dark brown tinting may be due to the presence of tannic acid from decaying oak leaves and other vegetation aboveground.

24. These small, thin stalactites in the same cave are called soda straws for obvious reasons. The points of light at their tips are drops of water poised and ready to fall to the cave floor below. Also present are small example of bacon rind or drapery structures.

25. A closeup of the late Pleistocene-Epoch volcanic rock known as the Neapolitan Yellow Tuff, at Cuma, in the volcanic wonderland -- and potential urban disaster zone -- of the Campi Flegrei (Phlegrean Fields), north of Naples. This outcrop was created by ash flows and contains bits of rock that were ejected, sometimes from great depth, by an erupting volcano. Note my long-legged friend who came striding out of the shadows to be photographed. (See also Soils Gallery, No. 7.)

26. The sandy Tyrrhenian shore at Cuma is typical of much of the western Italian coastline from Naples to Rome and beyond. According to one widely used and modern classification scheme, this is a "leading-edge" coast, where rocky cliffs and erosional conditions are supposed to prevail. There is a little of that farther north, in the vicinity of Gaeta and Sperlonga, but for the most part the prevailing regime is the one shown here.

27. This looks like an attempt at an artsy duotone, but in fact this is a full-color image that captures the grim and sulfurous aspect of La Solfatara. This famous and geothermally robust landmark, also in the Campi Flegrei, is the most obvious indicator that the greater Naples region is sitting on top of a subterranean time bomb. According to the Geowarn website (see my Geology Links Page), this crater gives off about 1500 tons of carbon dioxide per day. It's also the perfect spot to have your sinuses cleared out by a strong dose of airborne sulfur compounds.

29. This modest set of Roman ruins, also in Pozzuoli, is the Serapeum or Temple of Serapis, one of the world's most famous geological sites. The columns that stand a little right of center each have a darkened zone below their middle where aquatic molluscs at one time bored into them. In other words, the columns were once largely submerged in the water. This demonstrates that the level of the land in this area has actually risen since the Middle Ages -- due to the emplacement of magma under the area's solid surface. Nor has this movement stopped. This photo was taken in 1976; about seven years later, the surface began to rise again, prompting fears that a new volcanic eruption in the Campi Flegrei was imminent. The columns rose almost completely out of the water. Even more recently, though, subsidence has resumed, and the temple area has lowered again somewhat.

30. And speaking of famous geologic sights: this is Mount Vesuvius from the Bay of Naples. Its most recent major eruption cycle ended during World War II. If a new cycle begins without much warning, it could be the greatest human disaster of the twenty-first century. Since the 1940s, Naples, like so many other metropolitan regions of the world, has experienced unchecked population growth, and now about 1.2 million people live in the shadow of this impressive but immesely dangerous landmark.

31. As one hikes up to the summit of Vesuvius, a clear view of Monte Somma presents itselt. This arc-shaped, partial outer rim surrounding Vesuvius is the caldera, or bowl-shaped collapse feature, of an older volcano that exploded about 17,000 years ago.

32. Up on the rim of Vesuvius. This great mountain, over 4,000 feet hight, is a stratovolcano -- a steep-sloped volcano composed of alternating flows of ash and lava. Various layers of these igneous extrusive rocks can be seen in the crater wall.

33. This rocky land- and seascape of Sardinia's La Maddalena Archipelago seems to be rising from the water -- or subsiding into it. Here the bedrock consists of granite or other granitelike units that were emplaced in the middle to late Paleozoic Era -- about 400 to 300 million years ago.

35. Mount Stromboli, as it appeared in 1977. This stratovolcano has been almost continuously active for the last two millennia, at least. Stromboli and its companion volcanoes of the Aeolian Archipelago are situated north of the nortwestern corner of Sicily. They may constitute an island arc near a subduction zone, but the Mediterranean is such a geologically complex region that we're simply not sure yet.

36. The dusty, windswept path up to Stromboli's summit. This and Photos 37 and 38 were taken in the summer of 1978. It is now at least officially forbidden to make this climb without a guide in attendance.

38. The rock shelter at the summit where, to escape the strong fumes from the crater and the sandblasting wind, two friends and I rested and enjoyed an open-air meal of cheese, sausage, and table wine purchased back down at sea level. As I look back on it, I think it was the best dinner venue of my life.

41. On the way up to Etna's business end. Notice the vast area of nonvegetated terrain -- an indication of how frequently the volcano repaves its slopes with new lava flows. Seen here are the Central Crater summit and the smoking Northeast Crater, as they appeared in 1978.

42. Much closer to Etna's summit. As with No. 40, this photo and Nos. 42-47 were taken in the summer of 1978. This may be a popular tourist venue, but the climb to the top from the access-road terminus is challenging for those not used to the relatively thin air of 10,000 feet above sea level. Such conditions did not deter the Roman emperor Hadrian in the second century A.D. To quote from the Augustan History: "He sailed to Sicily, and there he climbed Mount Etna to see the sunrise, which is many-hued, they say, like the rainbow."

43. Nor was Hadrian the only great name of the ancient world associated with Etna. Approximately five and a half centuries before the emperor's ascent, the Greek philosopher and physician Empedocles ended his earthly existence -- so the legend goes -- by throwing himself into an erupting crater here. This scene show Etna's Northeast Crater.

44. Fumes issuing from vents on the crater wall. Perhaps the most compelling things about visiting the rim of an active volcano are the frequent earth tremors, the fumes, the roar, and the sense that you have returned to the very beginning of things.

45. This moonscape on the crater's flank is littered with volcanic bombs -- globs of lava that solidifed in flight. Can you tell the direction of the prevailing wind from the patterns of sand-and silt-sized material trailing off behind around the stones? The deflation hollows between the bombs are places the wind has excavated without hin-drance from barriers.

46. A fissure and two small cinder cones that developed from it when it was active. The smaller cone, just right of center, is tinted wih bright sulfur deposits. Fissures can be the source of spectacular lava displays.

47. A splash of color in an expanse of battleship gray. While Etna gives off vast quantities of sulfur dioxide in gaseous form, this photo shows a deposit of native (elemental) sulfur.

48. On our remarkably frenetic planet, the Earth's exposed crust is attacked by the elements as soon as it's formed. This channel deposit of puckered mud or silt was derived from the chemical weathering of the unvegetated lava by rain or melting snow.

49. This photo and the two that follow were taken in 1976 in the spectacular Cueva de Nerja -- the Nerja cavern complex in Andalusia, east of Malaga. The caves are developed in dolomitic marble, laid down in the Tethys Sea of the Triassic Period and subsequently metamorphosed in late Mesozoic and Tertiary time. Prehistoric cave art, created by a Johnny-come-lately primate species, is found here, but -- pace archaeologists everywhere -- it can't compare with the magnificence and extent of nature's own artwork.

50. While the archaeological remains demonstrate that it was visited by earlier inhabitants of this region, the Nerja cavern complex was not discovered in modern times until1959. The speleothems on view here include a column (right of center) and many stalactites.

51. The violet and green tints in the background are the result of lighting that was supposed to improve upon nature's handiwork -- the geological equivalent of gilding the lily.

52. This sort of knife-edge ridge, formed by very steeply dipping strata, is a hogback. This feature stands along the road that connects the ancient Roman settlements of Maktar and Thuburbo Majus.

1. A scene from the road along the Red Sea Coast of the southern Sinai Peninsula. In this hot, dry, and forbidding environment, vegetation plays a minor role at best. The surface of the Earth's crust, here composed of ancient Precambrian metamorphic ans igneous rocks, is exposed to the full brunt of the sun and wind.

2. A fair approximation of Planet Mars. Or it could be Earth for the vast majority of its own geologic history, before the plant kingdom established itself on dry land and provided a living mantle that slowed the process of erosion. In fact, it shows a small slice of tghe modern Earth -- the same section of the Sinai shown in the first photo. The forces of weathering turn once solid outcrops into sheets and piles of loose rubble.

5. Not far from the redbed region is a more extensive domain of cliffs and canyons of a strikingly different type. This area, part of the large Geologic Reserve of Haute Provence, contains sequences of rock layers spanning some 300 million years of Earth history. Prominent among these vast piles of strata are pale Jurassic-Period limestones, orignally deposited in the long-vanished Tethys Sea and subsequently thrust into the underside of Europe.

6. This towering cliff of limestone represents a vast span of time by human standards, but well over nine-tenths of geologic history to date was already over when the first layer of lime mud, destined to be the lowest stratum in this cliff, was deposited. The formation of the Alps and the almost complete disappearance of the Tethys Sea are the results of plate collision, involving southern Eurasia, northward-moving Africa, and other land masses as well.

9. The fact that these strata in the Daluis Gorge dip down toward the right is a clear indication that this region has experienced significant tectonic disturbance. Actually, that's putting it mildly: in parts of the Maritime Alps, large blocks of the Earth's crust called nappes have been thrust many miles over preexisting rock units.

10 .Farther south, the Var River widens into a braided stream. This type of drainage can be caused by several different factors -- for example, by easily eroded banks (which doesn't seem to be the case here) or by the introduction of sediment load that is simply too much for the stream to carry. The result is a number of small channels water winding their way through exposed rubble bars.

11. The floor of the Var Valley where a rather fragile-looking one-lane bridge crosses the braided bottom. Note the large rubble deposits, some of which have been stabilized by vegetation. This great volume of rock debris is testament enough that the Maritime Alps, like all mountains, are subjected to relentless erosion.

13. This view, also looking southeast, better displays several of the magnificent normal faults visible on the canal walls. Look for the high-angle fault traces on the right side; they are the slanting lines between the offset lines of vegetation.

14. Facing northeast. Here the faults are even more evident on the north wall. These strata of the isthmus between the Peloponnesus and the Greek mainland have recently been raised above sea level to form a horst, or upraised block. The Gulf of Corinth, just to the west, is one of Greece's many grabens, or downdropped blocks. The widespread presence of such features indicates that this crust has stretched apart in recent geologic time.

28. Looking in another direction within La Solfatara, one can see by its steep crater walls that it truly is a volcano in its own right -- an active volcano that sits that sits in the midst of the sprawling urban center of Pozzuoli. Some truisms bear repeating: this is not a good place for hundreds of thousands of people to live.

34. Exposed granite often weathers into oddly rounded, whimsical, Gaudiesque forms. The scooped-out features, perhaps caused by the expansion of salt crystals between the rock's mineral grains, is known as tafoni. This piece of natural sculpture is an outcrop on Isola di Caprera, in the La Maddalena Archipelago.

39. Mount Etna, the greatest of all Mediterranean volcanoes. This is a long-distance view from the northeast, in the lovely seaside town of Taormina, Sicily. Etna resists easy classification. It has been described as a shield volcano in its lower reaches and a stratovolcano in its upper; and it erupts different types of lava, sometimes simultaneously.

15. Et in Arcadia ego. A view of southern Greece's Arcadian Mountains, near sunset. The Arcadia district, in the heart of the Peloppenesus, is also a good place to see advanced karst (lmestone solution) landscapes, including poljes -- low areas, rimmed by high ground, that are much more expansive than sinkholes.