Volcanic eruptions and earthquakes shake southern Italy frequently, as they have for 12 million years. In that time, tectonic movement has split Calabria--the "toe" of the Italian boot--from what are today the islands of Sardinia and Corsica to the west, and formed mountain ranges. As part of the international Calabrian Arc Project, Lamont-Doherty scientists Nano Seeber and Meg Reitz are traversing Calabria to examine rocks and study the terrain to better understand this complex and violent history. Read about their work here.
Nano and I took the train to Rome to meet a colleague for lunch, and after we explored the old city. I have been through Rome a number of times, making my way to and from Calabria, but this was my first time really seeing the city. Nano was a fantastic tour guide. He was born in Florence but moved to Rome as a kid in the 1950s. He lived next to the Roman Forum before his family moved to Lanuvio.
By chance we discovered a fabulous museum–just three years old but built on the ruins of the Imperial forums, the Roman Empire’s political, economic and religious center. We walked through the same halls and archways that the Romans used while shopping for cloth and meat 2,000 years ago. The ruins and artifacts were beautiful on their own. However, the most fantastic thing about this museum was an exhibit unrelated to the ancient artifacts.
In the 1950s, film director Federico Fellini invited New York photograper William Klein to capture the Italy depicted in his films and these are the pictures we saw on display.
In one room, we encountered five photographs interspersed among limestone pillars, statues of Caesar, and pieces of the Temple of Venus. It was a setup I have never seen before, but somehow both exhibits became more powerful because of this juxtaposition.
This mixing is what strikes me most about Italian life. I noticed it in Caccuri, when I saw great great-grandmothers gossiping with great great-granddaughters on the street. Americans aren’t as proficient at fluidly mixing generations. I noticed it in Placanica, in southern Calabria, when Nano and I went to a town festival of the patron saint, Saint Antonio. Here, there were people of all ages sitting in the church, praying and leaving offerings. Outside the church, the scene resembled a dance club with loud music, dancing, yelling and laughter.
The juxtaposition was strange, yet wonderfully beautiful. In Rome I saw it again in the mixing between massive, ancient buildings and daily life. In pictures, those Roman landmarks, the Forum and Colosseum, look isolated and rural. But in real life they are integrated with modern street life. You turn your head to check for traffic, and see an ancient wall looming over modern buildings.
The most memorable sight came at the end of my trip. I was riding the train through the outskirts at Rome, staring at the farms just starting to appear on the landscape. The sun was setting over the Tyrrhenian Sea and casting long, orange rays across the fields. At just the right moment, I noticed a man seated on a bale of hay, his back to the setting sun. Just 200 meters in front of him, an enormous Roman aquaduct passed overhead–a blend of past and future.
How do we connect the two? How do we prevent ourselves from repeating our mistakes? Perhaps we need to do as the Romans do and intertwine the generations a little bit more.
I grew up in a family that drove on vacations, be it six hours to the beach, eight hours to see relatives, or three days to Idaho. So the seven hour drive from Calabria to Rome is no big deal, although the lack of air conditioning does make it undesirable. When I tell my friends from the Crotone Basin that I’m driving to Rome, I get astonished comments about the distance.
This year, Nano and I stopped to hike Mount Pollino, 2,250 meter peak in the southern Apennines, not far from where we were working. It makes me smile to imagine how the Calabrians would react if they knew we were driving to Rome and stopping for a five hour hike with a 750 meter elevation rise.
It was a beautiful hike and wonderful way to end the field season. Nano had walked it a few years before and was showing me the way. The trail is not easy to find, and even more difficult to stay on. At one point, he turned off a large dirt path onto a small one. I asked, “Why did you go this way?” He shrugged: “I follow the horses.” A true Calabrese response. It turned out the large dirt road also worked, but the horse path was definitely more pleasant.
Nano described the change in vegetation as we climbed; the Maggiociondolo, with their beautiful hanging flowers; the Fagi, a type of birch tree, but much more knobby; and the Pini Loricati, a stunning tree that lives only at high elevation, in harsh weather. They originated in the Balkans and migrated to the Apennines during periods of glacial advance.
Italians call them “Loricati” because their bark resembles the armor used by the Roman armies.
We hiked in four stages. First, we skirted the bottom of Serra del Prete, the mountain next to Pollino, and climbed 1,500 meters. Stage two was a long and steady climb to a large field, with a herd of cattle and a bar for hikers to stop for a café. Stage three was a steep climb to 2,000 meters, through Fagi trees and near the top, Pini Loricati. Stage four was rough, with 250 meters to go. Wind, no tree cover, unsteady footing on limestone blocks. At 2,150 meters we came across an old, sturdy Pino Loricato. How could anything live up here, much less thrive?
At the crest it’s one more valley, covered in snow, and one more peak to the summit. We rest and have lunch at the top, protected from the wind, and then slowly make our way back down and finish our trip to Rome.
One of the challenges of studying the Calabrian subduction zone is the enormous variation over relatively short distances. Etna is located just 120 kilometers from Stromboli, yet the volcanoes have completely different sources of magma. Fluvial conglomerates in the Crotone Basin have lots of chert, yet conglomerates of the same age just 15 kilometers to the south don’t have any.
On our last day of fieldwork, Nano took me just north of the Sibari Basin, at the southern tip of the Apennines, to investigate another dramatic shift. Here, we are looking at the transition from subduction to collision. An oceanic plate (like the Ionian Sea, east of Calabria) can be subducted easily: it’s made of oceanic crust, which is often colder, older, and more dense than the plate next to it. However, in space, oceanic crust transitions into continental crust, which is warm, young, and less dense. For example, the crust under the Atlantic Ocean is oceanic near the Mid-Atlantic Ridge, but continental off the coast of the United States.
The situation is similar in the Mediterranean. The Ionian Sea is made of oceanic crust but on its southern edge, the crust transitions into the African continental crust. In addition, just north of the Crotone Basin, the oceanic crust transitions into the Apulian Platform, a piece of continental crust that extends from the Gargano Peninsula to the Salento Peninsula. Since the Apulian Platform is too buoyant to subduct, the two plates are colliding, building mountains, and their convergence rate is slowing down. However, a few kilometers to the south, subduction continues and the convergence rate is steady.
To understand and work through this problem, I like to picture a comedic sketch in which someone carrying a two-by-four lengthwise tries to walk through a doorway. One side of the two-by-four hits the wall and generates the Apennines while the other side hits the wall and generates the Maghrebides in Sicily. Calabria is stuck in the door. Since tectonics continue to force Calabria through the open door, the parts that are stuck must somehow detach so that Calabria can push forward and continue subducting.
Most commonly, scientists think this process is accomplished through a vertical shear zone, or strike-slip fault. So the two by four behaves more like a piece of foam that will bend around the corners and eventually break completely. In the Sibari Basin, however, Nano and I have found little evidence of strike-slip faulting. Instead, what we’ve found are normal faults that are moving rocks near the surface through the doorway, while leaving deeper rocks behind. In this way, the crust acts more like a layered cake, in which the bottom layer remains in the doorway while the top slides through on a slippery layer of frosting. We need a lot more data before we know which mechanism is working. The fun part now is thinking of other ways that Calabria might slip through the doorway.
After the memorable trip up Mount Etna, Nano went to the Southern Apennines, while my parents and I made the familiar trip (for me, anyway) across the Sila and into the Crotone Basin. I raved to my parents about the great beaches and wonderful swimming in the Ionian Sea; I reminisced about my time on top of the Sila hiking through pine forests and the Switzerland-like lakes up there; I told them stories about the wonderful old towns nestled high on the rocks all over Southern Calabria. But when we arrived at the agriturismo, all they were interested in doing was getting up early, hopping in the car, and driving to outcrops to help me collect data.
Over the course of two days, we hunted down Upper Messinian conglomerates to help me and Nano with our research of the Messinian Salinity Crisis. My parents became master rock identifiers as we counted ratios of chert to granite clasts within each conglomerate. This information helps to determine the “provenance” of the deposit, or what kind of rocks the river eroded.
They also learned how to tell what direction the river was flowing in– a tricky task. We looked for imbricated clasts. These are clusters of thin, flat clasts (not round ones) that are pushed by the current until their flat side is facing upstream. We measured the direction that the clasts were stacked to determine which way the river was flowing. With these two pieces of information (clast provenance and current direction) from a number of outcrops around the area, we are able to recreate the Crotone Basin’s drainage flow.
My parents were struck by the tranquility of my field area. We passed through a few small towns on our first day working, but the second day we drove 50 kilometers and saw only fields, cows, and goats. What I really wanted to show my parents was the attitude of the people.
The sense of family and community in Southern Italy is overwhelming. The workers at the bar we went to in the morning remembered me from last year and gave my parents special treatment while we were there. The farmers we passed stopped their tractors and asked us about ourselves.
If you are not careful, you can be trapped in an hour-long conversation. People are more important than work here.
For dinner on our last night together, I took my parents to Canciumati. The family was excited to meet my parents. Mario, the patriarch, told them that when I was in Italy, he considered me his daughter. They served us four huge courses and sent my parents home with two bottles of wine. They had adopted me and, now, my parents into their family. It’s a hospitality that is indescribable, and the heart and soul of this place.
Boris and Alfio, geologists at Sicily’s National Institute of Geophyscis and Volcanology picked us up in their four-wheel drive jeeps. Etna is a stunning image. She rises 3,300 meters right from the seafloor, towering over the towns located around her flanks, providing fertile land for farming and beautiful hiking and skiing. Alfio calls her their “Sicilian Mother”: bountiful and beautiful, but able to flare up at a moments notice.
We drive up the base of Etna studying the lava flows visible on the road cuts. Lava from a 1690 eruption traveled 45 km to Catania, destroying much of the city, before pouring into the Ionian Sea. As we make our way up the lava gets younger: 1700s, 1983, 1991-2, until we finally reach the tourist center where lavas in 2001 and 2002 lavas destroyed several buildings. There is a cable car that takes people from the tourist camp to 2,500 meters. The cable car was first built in the 1970s so people could more easily reach the summit. Periodic lava flows have destroyed it four times in 40 years. The current one was rebuilt after the 2002 eruption.
At base camp, we stop to pick up Doug and Diane, two videographers accompanying us up the mountain. Boris and Alfio also grab a caffé (an Italian staple). We pass through the gates for authorized personnel only, getting annoyed looks from the tourists who have to pay to ride the cable car or trudge up themselves.
We’ve driven about halfway up, when we notice two large hills covered with ash towering over us. In 2000, the area was a flat expanse of ash without these features. Within a year, magma beneath Etna had generated these two massive cones.
Boris says that every time he comes up to Etna he takes dozens of photos and that in the seven years has accumulated hundreds of photos of features that are no longer part the landscape. We so often think of mountains as slowly growing features that may set off an earthquake every few decades, but rarely change within our lifetime. And here is Etna that, like all active volcanoes, changes completely every few years, even without a major eruption.
We park the jeeps around 2,800 meters and begin to hike across thick deposits of windblown ash. We can see traces of snow that fell this year or several years ago, preserved under the ash. The walking gets tough as the ground turns to lava called A’a (for its Hawaiian counterpart).
A’a is crumbly, sharp, and painful to grab onto if you lose your balance.
Further up we start to see rocks of hydrothermal origin. These are composed of minerals that crystallize from water heated inside Etna (sulfur is the most common mineral). We’re still far from Etna’s active caldera, so these are rocks that were ejected from the caldera during Etna’s numerous explosions, or burps as Nano calls them.
We make the last scramble across a 40 degree slope to edge of the Etna’s most active caldera, where enormous fountains of lava erupted in 2008.
Over a period of eight months, 66 lava fountains gushed into the air. (Compare this to Mauna Loa’s 46 lava fountains in three years.)
So here we are, standing right next to it.
The rocks are coated in soft ash from explosions earlier this year, in April. They are warm to the touch from the magma just beneath the surface. Walking around, we come across vents of hydrogen sulfide under our feet. If the breeze blows the wrong way for too long, the smell of rotten eggs is overwhelming, burning your eyes, nose, and throat. Boris said he’s breathed in so much hydrogen sulfide, he has destroyed much of his sense of smell.
The trek back down Etna is treacherous, but beautiful. It’s a relief to finally make it back to the soft ash and our jeeps. Those of us here for the first time – myself, my parents who are visiting from Massachusetts, Doug, and Diane are nearly speechless with awe and wonder.
The next morning Boris calls to tell us that the caldera edge we were hiking along had collapsed into the caldera. The powerful, scary Etna had changed the landscape once again. I agree with Alfio: a Sicilian Mother after all.
Italy has some of the most famous volcanoes in the world: Vesuvius, Stromboli, and Vulcano all lie in a chain along Italy’s western coast. Scientists have found that these volcanoes are all intricately linked to the subduction of the Ionian Sea beneath southern Italy, Calabria, and Sicily.
An oceanic plate contains rocks that have a lot of water in them (not surprisingly). This water is not just sitting in the pore space of sediments, but it is bound into the crystalline structure of the minerals that make up the oceanic crust, as water.
When the oceanic plate reaches depths of about 100 kilometers during subduction, temperatures and pressures become large enough that the water bound in the minerals becomes unstable and is released into the mantle. Water enters the mantle (where no water was before) and lowers the melting temperature of the mantle rocks, so small amounts of rock begin to melt where an oceanic plate is subducting.
This melt then rises through the crust and generates volcanoes at the surface.
These are known as subduction volcanoes, or arc volcanoes, and every active subduction zone has a chain of volcanoes generated by the addition of water to mantle. For example, in Japan, the Pacific Plate is subducting under Asia; in Chile, the Pacific Plate is subducting under the South American plate; and in the northwest United States, the Juan de Fuca Plate is subducting beneath the North American Plate (creating volcanoes like Mount St. Helens).
Although subduction volcanoes dominate Italy’s west coast, it’s largest and most active volcano is not related to subduction. Mount Etna is located in eastern Sicily and stands over three kilometers (11,000 feet) above the ocean. It is one of the most active volcanoes in the world, spewing ash, lava, and gas nearly as often as Mauna Loa in Hawai’I (which erupts, on average, every 3.5 years).
So how do scientists know that it is not an arc volcano, even though it is so close to a subduction zone?
The chemistry of the lavas.
Geochemists analyze the chemical make-up of lavas erupted all over the world to determine their origin. For example, magnesium and iron are found deep in the mantle while potassium and quartz are only found in the crust. Mount Etna’s lavas are rich in Magnesium and Iron, but also have a lot of potassium.
So where is the lava coming from? We are collaborating with geochemists at the National Institute of Geophysics and Volcanology (INGV) in Catania, Sicily to try to figure out just that. Tomorrow we climb up Mt. Etna to look at its most active caldera (responsible for lava flows in 2008 and explosions earlier this year) to learn about Etna’s history and talk about why this immense volcano is even there.
The Crotone Basin accumulated sediments for nine million years before the forearc uplifted above sea level. Each layer of sand, clay, and conglomerate in the basin contains information about the environment at the time that layer was deposited.
About six million years ago, halite and gypsum were deposited in the Crotone Basin. Geologists refer to both rocks as evaporites. All bodies of water on the Earth’s surface contain dissolved ions, most commonly sodium (Na+), chloride (Cl-), magnesium (Mg2+), calcium (Ca2+), and sulfides (SO42-). When water starts to evaporate, the dissolved ions bond together and precipitate out of the solution, forming evaporites (halite = NaCl, salt; gypsum = CaMg2SO4). Most commonly we find evaporites in deserts environments that sometimes receive influxes of water, like the Great Salt Lake in Utah. Since halite and gypsum are found in the Crotone Basin, we think that water must have evaporated from the basin about six million years ago.
As it turns out, evaporite deposits are found across the Mediterranean Sea during the same time period. Drill cores have turned up three kilometers of evaporites in some areas. To crystallize this much salt over such a wide area, geologists think that the entire Mediterranean Sea must have evaporated–an event called the Mediterranean Salinity Crisis (or Messinian Salinity Crisis) which lasted from 5.96 million years ago to 5.33 million years ago.
The Mediterranean Sea is located in the desert latitudes, where evaporation exceeds precipitation. The water level remains constant because water from the Atlantic Ocean enters the basin through the Straits of Gibralter.
But this wasn’t always the case. During the Messinian, a global sea level drop and local tectonics caused the land at the Straits to rise, cutting off the Mediterranean from the ocean. Since evaporation was so high, the water level dropped, concentrating the dissolved ions, and crystallizing evaporites; just like the Dead Sea in Israel, which crystallizes halite on its seafloor. Halfway through the Salinity Crisis, the four kilometers of water that filled the Mediterranean disappeared. A vast, desert basin is all that remained.
Nano and I are studying Messinian river deposits. Before and after the Salinity Crisis, rivers carried sediments from the mountains west of the basin. During the Messinian, however, something different happened.
The rivers seem to have flowed from east to west, exactly opposite from today. They may also have carried chert, a rock made of silica and formed only within deep ocean basins. Chert is not found in the mountains to the west, but is found offshore below current sea level. This suggests there may have been mountains east of the Crotone Basin during the Salinity Crisis.
So, how did the mountains form and where did they go? The water in the Mediterranean Sea pushes down on and depresses the crust, much as glaciers do on land. If water is removed (as it was during the Salinity Crisis), the crust rebounds. Therefore, uplift and local tectonics may have formed mountains of deep-sea rock east of Calabria. When the the Mediterranean Sea came flooding in, the mountains would have been obliterated.
The climate of the Crotone Basin is marked by cold, wet winters and hot, dry summers. We arrived last year, on our first trip, in the middle of a six-month drought that lasted from April to September.
I love how life figures out a way to flourish. Flowers in a riverbed; Snails on a thorn bush; Spiders spinning webs in a field.
Herds of sheep and goats roam the fields of the Crotone Basin. We were hiking through these fields and met a goat herder and his dogs. Herders often share invaluable information about the land, and show us useful paths and roads through the maze of brush and thorns.
The goats are amazing creatures. They can climb trees and stand on the small branches to find tasty leaves; they are wonderfully agile.
Fences like this are found across Calabria, to protect harvests from goats, sheep, and cattle herds.
This is an example of a gate in one of these fences: just slipping the loop of wire off the top opens the gate. It’s a wonderful contraption that keeps herds in their place, but allows people to go anywhere.
Fires are a common sight in June in the Crotone Basin. After the wheat harvest (going on right now), the farmers burn their fields to resupply nutrients and prevent wildfires during the dry season.
Near the town of Casabona, farmers have been burning the grasslands surrounding the town to stave off wildfires later in the season.
Nano and I usually take a packed lunch of panini (sandwiches) and fruit with us into the field. Around midday, we start looking for trees to shade us from the sun while we eat. Sitting by Lake Ampollino for lunch one day, Nano and I were joined by a neighboring dog that got our scraps.
Last year I was collecting a sample of sediment from a riverbed and spent the day walking up the Neto River to find a good location. When I finished, I noticed a road high on one side of the valley. I climbed to the road and found a tunnel with no lights inside. I looked to see if I could walk around it but found only a shear cliff. My options were to climb back down into the river or walk through the tunnel. So, I began walking.
Gradually, the darkness took over. I stopped about 15 meters in, when I couldn’t see my hand in front of my face, waiting for my eyes to adjust. They never did. With my hand on the wall of the tunnel, I slowly stepped forward into the smell of rainwater and sound of creatures moving around. I thought I knew darkness, but not like this. After what felt like hours, I saw a light signaling the tunnel end and practically ran. When I reached daylight, my excitement was quickly dulled. Not 20 meters away loomed a second tunnel. I thought, “Hey, if I made it through the last one, I can do this one.” Then I see the sign “Galleria: 458m”. No way! Half a kilometer long! I turn back and see a sign from the tunnel I just walked through “Galleria: 427m”. Oh. I’m glad I didn’t see that sign on the way into the first tunnel. I shrug and begin walking toward the second tunnel. But then, I hear what sounds like a huge truck coming through the tunnel behind me. For the next three minutes, car after car after car come through the tunnels. When there’s a break, I begin to walk through the second tunnel. But before long, I see the light from a car coming behind me. Several more cars pass including one that stops just ahead but continues on. Eventually, I make it out of the tunnel and a car pulls over. In Italian, the driver asks, “Where is your car? The gate closes at 5 pm. What are you doing?” I tell him “My car is on the other side of the gate, don’t worry.” He looks back at the tunnels I just walked through and says, “Your car is on the other side?” “Yes,” I say, “Don’t worry.” He gives me a skeptical look and drives off.
This year, Nano and I traveled the same road but when we turned around we found the gate shut. We were locked inside the road! Just as I was about to attempt picking a lock for the first time, a man pulled up on the other side and called his father who arrived 10 minutes later with the key.
Nano and I have arrived in the Crotone Basin, where we’re staying in a place that Italians call an “agriturismo,” which is like a bed and breakfast that also serves lunch and dinner. Our little place is unique even among agriturismos. It is called Canciumati (can-chew-ma-tea), a house with four generations living under one roof. The family rents three rooms on the first floor to tourists, visitors, and friends, that remain unoccupied most of the year. For income, the family depends on the olive grove that surrounds the property, which also supplies the olives and olive oil we’ve been relishing. Calabria’s hot, dry summers and cold, wet winters provide the perfect conditions for the trees to flourish.
Last year, Nano and I visited an agriturismo that has a 2000-year-old olive tree on its property! For the first part of our field season, Nano and I will be in the Crotone Basin in the forearc of a subduction system. Usually, the forearc is found below sea level, but in Calabria parts of the forearc are located 1200 meters above sea level. What difference does that make? I’ll put it this way: one million years ago, before Calabria began to rise, Italy did not have a toe to its boot, and only a few islands would have existed between Salerno and Sicily!
We are trying to determine how and why this uplift began. Nano and I have identified a surface that we think existed near sea level one million years ago. This surface is a geological “contact” between the granite bedrock of Calabria and a fluvial conglomerate, or river deposit, on top of it. A contact is the surface where two different types of rock are touching. Contacts can be sedimentary, related to changes in deposition (a clay bed on top of a sandstone bed) or tectonic, related to faulting. The sedimentary contact we are measuring is now high above sea level and has been eroded and dissected by rivers, so it is only present in small pieces. To map this surface, we are walking up river gorges, climbing mountains and traversing numerous goat and cow paths until we see the contact. Then we record our location with GPS (latitude, longitude, and elevation), take pictures, sketch and record interesting features and move on to find another contact.
When we put all our points on a map, we will be able to see the shape of the surface. The shape (or morphology, as geologists call it) of the surface will reveal much about how the land was uplifted: if the surface we map is now flat, then the land must have risen straight up. This is like submerging a piece of ice in water and then letting go, the ice will rise straight up to the top. If the surface we map is now tilted, then the land rose faster on one side than the other. It’s like opening a cooler. When you grab the handle and start to pull it open, the side by your hand raises high into the air while the side connected to the hinge remains close to its original starting height.