Driving around the island visitors can see the different aspects of the rocks that arise from a number of various geological events that, during the millenniums, have defined the original profiles of the coast. Therefore, fans of geology will appreciate the features of the rocks and the history of the origin of the island of through this detailed technical report.
The island of San Pietro was formed between 18 and 13 million years ago by intense volcanic activity, both effusive and explosive, whose products can currently be seen on the entire island. Until today many rock types have been recognized as both lavic and pyroclastic, whose variety and unique composition make the island an extremely attractive destination for a geological excursion.
The San Pietro Island rocks are formed primarily of ignimbrites streams (composition that varies from dacite to rhyolite to comenditic) from domes and lava flows of comenditic composition which are a rarity in this type of volcanic activity.
The official scientific name for Comendite originates from a region called Comende island, where they were discovered for the first time in 1895.
The island of San Pietro can be divided into four sectors based on geological and morphological characteristics:
• Center-Western Sector
Featuring more marked high grounds, formed by succession of domes and of lavic and comenditic flows
that can be observed in the areas of Borrona, Nasca and of Tortoriso which underlie the various layers of younger riolitic and of dacite ignimbrites (erroneously called by some trachytes). This type of geological structure forms in the north and in the South of the island. Often have a columnar fracturing and are well sealed, so as to resemble the lava.
• Northwestern Sector
Characterized by hills formed by small plateau of younger ignimbrite, near tall cliffs along the coastline where ash, pumice and tuffs deposits are located (the Bianche Tacche site). At the summit, accessible from the ground, one can observe the ignimbrites rocks with large cavities, due to the presence of gas bubbles and magma that originated them.
• Center-Western Sector
In this area you can find the most ancient volcanites of the island, whose flows are clearly visible in the Becco bay. To the north can be found ignimbrites rocks of a younger age, very fractured (the area of Capo Sandalo). Walking down the path that leads to the sea in Capo Sandalo it's possible to reach a little plaza where you can observe both comenditic ignimbrite and younger lavic ignimbrite.
• South-Eastern Sector
The oldest volcanic succession of the island, emerges on the south coast only in Punta Nera area. The sector is mainly dominated by layers of younger ignimbrites rocks, and of a low pressure area covered by recent sedimentary deposits. This old volcanic succession is visible along the south coast, in Punta Nera. Near a couple of beaches (like Girin beach ) it's possible to see the few island outcrops of sedimentary rocks formed during the lowering of the sea level .
Retrieved from: Unica.it
To know more about the terminology: Gruppo Nazionale di Vulcanologia
Link to Article - CARLOFORTE GEOLOGY
Punta Nera is just past the curve leading to Girin beach. It’s an ideal beach for families with children, because it can be reached by car, although one must then park on a dirt road at the entrance of the road.
The beach is a wide strip of fine and warm sand. It’s very large and divided into two parts by an artificial stone dam that protects the beach from the mistral winds and waves. Sheltered from the wind, surrounded by private houses gardens and local vegetation, it overlooks the island of Sant'Antioco and its waters aren't immediately deep.
On th Continua...
Capo Sandalo, situated on the western tip of the island of San Pietro, is an extraordinary cliff overlooking the Mediterranean Sea.
Here stands the lighthouse of the same name, built in 1864 with blocks of stone carved with a chisel and constructed in a cylindrical tower that supports an optical rotating lens with a focal length of 700 mm.
The lighthouse emits a group of four white flashes every 20 seconds; it has a light range of 34 miles and a geographical range of 24 miles.
Visible from 322 ° to 191 ° and 311 ° to 322 ° to the Continua...