After the continents of Africa and Europe collided, forming the Alps, the Apennines rose from an ancient sea. Starting about 20 million years ago, in several stages, tectonic forces pushed the mountains up and stretched them apart.
Since 1992, Italian geologist Sandro Montanari has run a basecamp– the Coldigioco Geological Observatory—in the Apennine foothills for researchers and students exploring the region. (Lizzie Adkins)
David Barbeau visited Coldigioco in college, and in spring 2013, returned with a group of Columbia and Barnard Earth & Environmental Science majors. Rocks from this region helped prove that an asteroid killed the dinosaurs, making T-Rex one of Coldigioco’s unofficial mascots.
A natural story teller who wears a small harmonica around his neck, Montanari’s geology lectures often include tangents on Italian art, music and culture. (Barbeau)
A normal fault created this horst, or promontory, above Frasassi Gorge, where a 200-million year old limestone cliff is visible behind seniors Siobhan Campbell and Claire Mathieson.
As a student in high school, Montanari and the local caving club discovered the Frasassi caves in 1971. Stacked seven stories deep, the caves were created as upwelling water dissolved one carbonate floor at a time while tectonic forces placed a fresh rock layer in the water’s path.
The “Room of Candles” formed through the steady drip of rainwater over the cave’s calcium carbonate ceiling. Over time, stalactites fallen from the ceiling continued to grow on the cave floor, building up stalagmites.
Near Frasassi caves, the smell of rotten eggs grows stronger. Groundwater reacting with 215-million year old gypsum has produced hydrogen sulfide that migrates to the surface along a thrust fault. Barbeau shows senior Caitlin Dieck the fault’s orientation and displacement.
Just up the road from Coldigioco an outcrop of pink limestone holds evidence of the K/T boundary 66 million years ago. Campbell points to the level of the extinction crisis.
Just beyond the red-tiled roofs of Gubbio, is the world’s best known K/T outcrop.
At the Gubbio outcrop, geologist Walter Alvarez found evidence for an asteroid impact that wiped out half of all life on Earth, including the dinosaurs. Junior Frankie Pavia pictured.
At another K/T outcrop, this one in Furlo, junior Reid Dubois Jenkins and Mathieson search for the extinction layer with hand lenses
Clues to look for include glass spherules, blasted into the atmosphere from the impact itself, and changes in foraminifera species. Campbell, seniors Sara Donatich and Naomi Wasserman pictured.
At the lower Furlo quarry, 60-million years of Jurasic-era sediments are exposed, extending from 201 to 144 million years ago. Jenkins walks toward a mother lode of submarine fossils.
Senior Kelsey Umemoto collects ammonite fossils, an extinct relative of the chambered nautilus.
Gubbio’s pink and white medieval buildings are made of the same Cretaceous limestones that we have visited in quarries across the Umbria-Marche region.
In 1976, Alvarez convened a group of geologists at the Ristorante Bottaccione to propose that the Gubbio outcrops be designated the official K/T boundary reference point. Their names, and the geologists who have come after, fill three registers.
Near the end of the Cretaceous period, an earthquake in present-day Furlo triggered an undersea landslide and turbidity current that created the white turbidite bed above in minutes. By contrast, the pink layers of microfossils above and below accumulated over hundreds of thousands to millions of years.
The crumbly rock at Massignano Quarry near Ancona recorded the period about 34 million years ago when ice formed on Antarctica. Barbeau collects ash samples from this global reference section for the Eocene-Oligocene boundary.
High iridium levels have been measured at Massignano Quarry, too, just before the E-O boundary, about 35 million years ago. Impact craters of the same age have been found in Siberia and Chesapeake Bay. Umemoto looks for impact spherules.
About 6 million years ago, tectonic forces closed off the Mediterranean Sea from the Atlantic Ocean, turning the sea into a desert. Remnants of this period, the Messinian Salinity Crisis, can be found on the Adriatic coast near Ancona.
As the Mediterranean withered away, a mix of salt, gypsum and organic shale built up on the seafloor. The shale in Jenkins’ hand smells like motor oil.
The oceans became anoxic and a third of marine invertebrates went extinct about 93 million years ago during what’s called Ocean Anoxic Event 2. In a quarry near Gubbio, the students are measuring the layers below this dark shale known as the Bonarelli layer.
Breaking into groups, the students measure the 400,000-year interval below the Bonarelli at different outcrops. Their goal: to see if the orbital variations that control Earth’s climate on 100,000 year cycles are imprinted in rocks across the region.
While they work, Sidney Hemming collects mud samples for dating at Lamont.
The students spend their last day on MatLab, analyzing their measurements and presenting and comparing their findings.
Pici alla carbonara is their reward. In the morning, they will head for Venice and then Milan, ready to fly home and finish the semester.
Tourists flock to Italy to see Michelangelo’s David and other iconic hunks of Renaissance stone, but in a trip over spring break, a group of Columbia students got to visit rocks that have shaped the world in even more profound ways. In the limestone outcrops of Italy’s Apennine Mountains, geologist Walter Alvarez collected some of the earliest evidence that a massive fireball falling from space some 66 million years ago was responsible for killing off the dinosaurs. Geologists have trekked to the region since then to study that catastrophic event as well as others imprinted in these rocks.
In March, it was the Columbia students’ turn. Led by Steven Goldstein and Sidney Hemming, scientists at Columbia’s Lamont-Doherty Earth Observatory, and visiting scientist David Barbeau, the students touched evidence of undersea mudslides, the drying of the Mediterranean Sea, and several extinction crises, including the one that ended the Age of Dinosaurs.
From about 200 million years ago to 6 million years ago, the vast, shallow Tethys Sea covered much of the Apennines, in Italy’s Umbria-Marche region. As the tiny plants and animals that lived in the sea died, their shells and skeletons piled up, leaving a record of the environment in which they lived. Later, tectonic forces rearranged this landscape, forming the Apennines in several bouts of squeezing and stretching. The activity left limestones made up of tiny microfossils exposed on land, providing a page-by-page story of the past.
More than any other geologist, Alvarez and his late father, Luis, are responsible for putting these rocks on the map. Now a professor-emeritus at University of California, Berkeley, the younger Alvarez began his career at Lamont-Doherty Earth Observatory in the late 1960s at the height of the plate tectonic revolution. In the 1970s, Alvarez traveled to the Bottaccione Gorge in Gubbio to measure magnetic reversals recorded in the rock to understand how seafloor spreading had moved Earth’s continents. Earth’s magnetic field periodically flips, leaving invisible stripes on the seafloor where magma rising from the mantle is magnetized in a northerly or southerly direction. These stripes also showed up in the Apennines, and Alvarez hoped that by dating them using the microfossils in each layer, he could learn more about the movement of continents.
But he stumbled across another mystery. At about 66 million years ago, the one-celled Globotruncana foraminifera suddenly disappeared from the fossil record, replaced by a smaller, more opportunistic species. Separating the two species was a half-inch of mud with no life at all. Testing the clay, Alvarez discovered high levels of the rare element iridium-an element rare on Earth’s surface but common in space. In a 1980 paper in Science, Alvarez hypothesized that a large comet or asteroid had fallen to Earth, kicking up a dust layer that blocked out the sun, starving much of life on earth. The dinosaurs and more than half of Earth’s species died during this time, marking the end of the Cretaceous period and start of the Tertiary, or in geology jargon: the K/T, boundary. In the late 1970s, two geophysicists searching for oil off Mexico’s Yucatán Peninsula discovered a 110-mile wide crater but it was many years before the Chicxulub crater was conclusively linked to Alvarez’s theory.
Sandro Montanari met Alvarez on one of his field trips to Gubbio, and at Alvarez’s encouragement, flew to California to pursue a PhD in geology. Among other things, Montanari collected evidence for a mega-tsunami in the Gulf of Mexico triggered by a six-mile wide asteroid crashing into the Yucatán. Eventually, Montanari returned to Italy and with Alvarez, bought and restored a farming hamlet, Coldigioco, outside the town of Apiro. Since 1992, Coldigioco has served as a base camp for geologists working in the area. Barbeau spent a summer there as a student at Carleton College, so when his colleagues at Lamont were searching for a new place to take students on spring break, Barbeau suggested the Apennines.
In the weeks leading up to the trip, the students read scientific papers detailing the discoveries made in this region and took turns presenting the material in class. They covered Italy’s tectonics and the evidence for several mass extinctions recorded in the Apennines’ exposed marine sediments of the Apennines—the K/T extinctions 66 million years ago; the Paleocene-Eocene Thermal Maximum, about 55 million years ago, when a rapid warming of the planet killed off many species, leading to the rise of some modern mammals; and the Eocene-Oligocene extinctions, about 34 million years ago, marked by a rapid cooling and the emergence of ice on Antarctica.
They would also study the drying of the Mediterranean Sea in an event called the Messinian Salinity Crisis, about 6 million years ago, and how scientists, including Lamont’s William Ryan, pieced the story together from sediments collected at sea; and the formation of the Frasassi Caves, discovered by their guide, Montanari, as a teenager. One day after their plane landed in Milan, they were on the ground, seeing, tasting and touching the places they had read about.
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