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The Sirente Crater Field
The first impact structures in Italy
Impact crater geology has been integrated as an important part of the planetary research conducted at IRSPS. Studies of craters in images from Mars, Venus and other bodies in the Solar System are combined with fieldwork on terrestrial craters. Projects are currently carried out on craters in many different parts of the world (e.g. Mongolia, Africa).
The first impact craters in Italy have been recently discovered in the Abruzzo mountain range. They form a crater field of more than 20 structures and they are extremely well preserved, having a very young age (about 1500 years).
The Sirente crater field is in the Sirente-Velino Regional Park, in the Abruzzo inland. It is located in a small mountain plain, called Prati del Sirente, just North of the Sirente massif (2348 m)
The Sirente Crater Field has been discovered by Jens Ormo in late '90 during his post-doctoral period at IRSPS. A research group was immediately formed, together with Angelo Pio Rossi and Goro Komatsu The main structure, currently occupied by a small seasonal lake, first attracted the attention of the research group, which started working about 2 years ago. A profile of the discoverers is available in this page.
The crater field consists of a larger structure, currently filled by a temporary lake, and several smaller craters, scattered in the western portion of Prati del SIrente plain.
Various studies have been carried out on the Sirente crater field in a few years following the initiation of the investigation, including detailed morphometric measurements, drillings, excavations and geophysical surveys. Further studies are currently ongoing.
History of the discovery
During the first reconnaissance trip to the lake it was clear that the lake was larger than first expected and that it showed a striking resemblance to small impact craters known from other areas in the world. Due to the geological setting of the lake and its voluminous elevated rim it was soon clear that is origin was not compatible with karst.
After ruling out some other alternative causes of formation based on the local geology (e.g. volcanic), only three plausible alternatives remained: periglacial feature (i.e. Pingo), a man-made water reservoir, or an impact crater.
The morphology of the main crater was studied by detailed leveling of the elevated rim and close surroundings. This gave that the elevated rim rises about 2.2 m above the surrounding plain and that it is 15 m wide. It was also evident that the lake was slightly oval with a maximum rim-to-rim diameter of 140 meter. The studies continued with core drillings, one near the centre of the lake (7 meters in length) and two on the elevated rim (3 meters and 5 meters in length). The core drillings confirmed that the lake depression is developed entirely in soft sediments. Radiometric carbon dating of material in one of the cores from the rim gave that the elevated rim is formed by overturned material in a way typical for impact crater rims, and that the age of formation could be set to the 4th or early 5th century AD.
The partial excavation of two of the small craters in the field allowed to study their internal structure, also ruling out a karst origin for them as well.
Theoretically, an impact crater of the size of the Sirente lake depression cannot exist alone. It must be surrounded by a field of small craters. This is due to the fact that small cosmic objects that approach the Earth would fragment during the passage through the atmosphere, producing a cluster of craters on the surface. In the case of sirente the biggest fragment should have produced the main structure, with a prominent rim. The spatial distribution of the craters in the field allow us to hypothesize a roughly NW direction for the incoming object.
Usually the velocity of such objects (e.g. asteroids and comets) when they impact the Earth is about 20 km/second (but it can vary). It is more than 20 times the velocity of a bullet from a high-velocity rifle. The collision with the atmosphere generates so high stresses in the object that it breaks apart. Only objects forming craters larger than about 1 km in diameter can survive the passage through the atmosphere as reasonable coherent bodies.
How to reach the crater
The Sirente Crater field is located in a protected area, in the Velino-Sirente Regional Park, inside the Secinaro municipality. If you plan to visit the structures please keep this in mind.
Take the A24, continuing on A25 highway towards Pescara. Exit at AIELLI-CELANO. Continue on S.S. 5bis. Just before entering Rocca Di Mezzo turn on the right for SECINARO. The crater about 7 km far, on the right.
Take the A14 towards south. After PESCARA-NORD take the next exit for the A25 highway (Pescara-Roma). Exit at AIELLI-CELANO. Continue on S.S. 5bis. Just before entering Rocca Di Mezzo turn on the right for Secinaro. The crater about 7 km far, on the right. You can alternatively (beautiful landscape!) exit at PRATOLA PELIGNA-SULMONA, passing through RAIANO, CASTELVECCHIO SUBEQUO, SECINARO, ROCCA DI MEZZO (beautiful landscape!). The crater is after few km on the left.
Literature on Sirente
Ormo, J., Rossi, A. P., Komatsu, G. (2002) The Sirente crater field, Italy. Meteorit. Planet. Sci., V. 37, No. 11, 1507-1522. Link to abstract
Ormo, J., Rossi, A. P., Komatsu, G., Marchetti, M., De Santis, A. (2002) The discovery of a probable well-preserved impact crater field in Central Italy. Lunar and Planet. Sci. Conf, XXXIII. Link to pdf file
Ormo, J., Rossi, A. P., Komatsu, G. (2001) Sirente: a possible small impact crater in Italy. Suppl. Meteorit. Planet. Sci., 36, A54.
Ormo, J., Rossi, A. P., Komatsu, G. (2001) The Sirente structure, a possible well preserved Holocene impact crate in the Appennines, Italy. Impact markers in the stratigraphic record. Sixth ESF-IMPACT Workshop, 83-84.
Santilli, R., Ormo, J., Rossi, A. P., Komatsu, G. (2003) A catastrophe remembered: A meteorite impact of the 5th century AD in the Abruzzo, central Italy. Antiquity, 77, 296.
Ormo, J., Rossi, A. P., Komatsu, G. (2002) The discovery of the Sirente Crater Field. Tumbling Stone, 18, Spaceguard Foundation and NEODyS. Link to article
ContactsFor information on the Sirente crater field and related activities at IRSPS please contact:
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