Archive for June, 2013

Pillow basalts for Dr. Pollock

June 4th, 2013

PillowsCastle060413CATANIA, SICILY, ITALY–These are Dr. Meagen Pollock’s favorite kind of rocks: pillow basalts. Above we have a spectacular example of pillow basalts exposed in cross section below a castle ruin in Aci Castello a few kilometers north of Catania. The pillows (more are shown below) are in the middle of this natural outcrop carved by the sea.

Pillow basalts are formed when basaltic lava is erupted underwater. The surface of the flow quickly cools and begins to solidify as the interior fills with lava. The result is a flattened spheroid of basalt with chilled margins. The castle, by the way, was built in 1076 by conquering Normans.

Megapillow060413The light was not great for this shot, but you should be able to make out in the lower right a large body of basalt with columnar joints radiating from the center. This is, I was told, a “megapillow’ of basalt from a large flow.

PillowWall060413Here we have a closer view of the pillows in the wall shown above. On several of these pillows you can just make out a fine-grained chilled margin.

PillowBed060413This is a view of the wave-eroded platform below the castle showing the pillows form the top. I left the roasting Europeans in the frame for scale. Note that while these pillows appear with almost circular outlines in cross-section, they are actually serpentine in shape.

These pillow lavas were formed with the beginning of volcanic activity roughly 600,000 years ago that led to the present Mount Etna complex. They show the submarine phase of eruption before the eruptive center was uplifted above sea level. They are the most spectacular pillows I’ve ever seen.

Exploring Mount Etna

June 3rd, 2013

MountEtna060313_585CATANIA, SICILY, ITALY–The International Bryozoology Association conference field trip began with a day on the magnificent compound basaltic stratovolcano that virtually defines the eastern half of Sicily: Mount Etna. We did not get to climb all the way to the top — that would have been a bit of an expedition — but we hiked around its diverse southern flank. The view above is looking toward the summit in the back left, a parasitic cone from an 18th Century eruption in the middleground, and in the bottom right is a trekkers cabin built (of course) almost entirely of vesicular basalt.

SmokingEtna060313Here is a closer view of the summit. The white smoke on the right is from active fumaroles near the top. Etna is one of the most active volcanoes in the world. Last month, in fact, it was erupting so much that a visit like ours today would not have been allowed. I ticked off a geological bucket list item: standing on an active volcano’s slopes. It is not close to the activity Dr. Pollock and her students have witnessed in Iceland over the years, but exciting for this paleontologist!

Sicily lies at the boundary between the African and European tectonic plates, producing an extremely complex geological situation that is still debated. We know, at least, that Mount Etna’s ancestors began erupting underwater about 600,000 years ago, and the axis of eruptive activity has slowly moved to the northwest. We are essentially looking at a series of successive volcanoes intersecting and overlapping previous versions.

Parco dell' Etna 060313This is the entrance we used into the national Parco dell’etna on the south side of the volcano. Note the perfect weather and the delightful contrast between the jet-black rock and greenery. There was less and less vegetation as we moved upslope.

ParasiticConeOutside060313This is the outside of a parasitic cone on the flank of the volcano. Through it emerged a lateral flow of lava.

ParasiticConeInside060313This is the inside of the same cone as above. The rest of it collapsed after the lava completely exited.

LavaTube060313The entrance to a lava tube. The lava flowed through its own hardened crust, leaving behind this rocky tunnel that looks very much like the ancient lava tube we visit on our Mojave Desert field trip. This particular one dates back to the 18th Century. Technically we’re looking through a window to the floor of the lava tube itself.

TreeLavaFossils060313Who says you can’t see fossils on an active volcano? These are basalt external molds of tree trunks formed when a flow of lava engulfed a forest. These are in the Parco dell’etna headquarters.

ParkOfficers060313When we visited the Parco dell’etna headquarters, we heard a brief presentation in the chapel of the abandoned monastery they occupy. The president of the park then addressed us. Can you tell which of the five people above is the president? (Hint: She’s wearing a scarf.) They are excited to announce that Mount Etna is now a UNESCO World Heritage site.

mineralpickingEtna060313Our last geological activity on Mount Etna for this week was a visit to the top rim of an eroded parasitic cone to find tiny little euhedral crystals of the mineral pyroxene (or, rather, a mineral from the pyroxene group). Here you see paleontologists in a very familiar pose but doing something distinctly unpaleontological.

NicosiaWines060313We ended the day at the very modern Nicosia winery where they grow the grapes in the rich volcanic soil on the slopes of Mount Etna. It was very interesting to see the industrial production of various types of wines, but I’m afraid the wine tasting was wasted on me.

We will visit Mount Etna once again when the full conference starts next week. I’ll have more images from a different part of the volcano. Tomorrow’s field trip is going to be along the seashore, so there will be some very different images.

A Wooster Geologist in Sicily

June 2nd, 2013

MountEtna060213CATANIA, SICILY, ITALY–This summer Wooster’s Team Italy consists of only me. Maybe in the future I’ll take students here for Independent Study projects depending on what I find. I’ve just arrived in the city of Catania on the eastern coast of Sicily. Above is a view of the gorgeous Mount Etna from the plane as we landed. This volcano dominates the city, both structurally and historically. More on that later. Twenty-three hours of travel through four airports has tuckered me out. Luckily we have an early dinner at 8:00 p.m.

I’m here for the 17th meeting of the International Bryozoology Association. It starts with a glorious field trip around the island. I plan to report daily as long as there is a wirleless connection.

Wooster’s Fossil of the Week: A shrimp from the Upper Jurassic of Bavaria, Germany

June 2nd, 2013

Aeger_tipularis_SolnhofenThe beautiful fossil shrimp above is Aeger tipularis (Schlotheim, 1822), and it comes from one of the most famous rock units: the Solnhofen Plattenkalk (Tithonian, Upper Jurassic) of Germany. (The Solnhofen is well known for its extraordinary fossils, including the fossil bird Archaeopteryx.) This shrimp is yet another generous gift to the Department of Geology from George Chambers (’79).

The shrimp in the Solnhofen are very well preserved. Note the long, long antennae and the tiny spines on the carapace. (I suspect, though, that parts of this specimen have been enhanced with ink by a commercial collector, especially the legs.)

SchlotheimFigure051813

Aeger tipularis was described in 1822 by Ernst Friedrich, Baron von Schlotheim (1764-1832), a prolific German paleontologist we profiled earlier. The drawing above is the original reconstruction by Schlotheim (1822, pl. 2, fig. 1; Solnhofen Lithographic Limestone, Solnhofen area; Lower Tithonian, Hybonotum Zone; width of figure 23.7 cm.)

References:

Garassino, A. and Teruzzi, G. 1990. The genus Aeger MÜNSTER, 1839 in the Sinemurian of Osteno in Lombardy (Crustacea, Decapoda). Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano 131: 105-136.

Schlotheim, E.F. von. 1822. Nachträge zur Petrefactenkunde (Addenda al Petrefactenkunde). Gotha, Beckersche Buchhandlung.

Schweigert, G. 2001. The late Jurassic decapod species Aeger tipularius (Schlotheim, 1822) (Crustacea: Decapoda: Aegeridae). Stuttgarter Beiträge zur Naturkunde, Series B, 309: 1-10.

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