Geology of Malta
The Geology of Malta consists of a sequence of
Tectonics
The
Formation of the islands
The
Nature of the sub-soil
The rocks are exclusively
The geological strata
The stratigraphy of the Maltese islands consists of five geological formations, ranging in age from late Oligocene to late Miocene.[1][5]
Oligocene
Lower Coralline Limestone Formation
The oldest exposed rock layer of Malta is the Lower Coralline Limestone Formation (
Miocene
Globigerina Limestone Formation
The Globigerina Limestone (
Since prehistoric times, this limestone has constituted the majority of building material used in Malta. Exposed to the air, the stone takes on a rosy colour, which browns with the formation of a protective patina. Lesser quality rocks can erode easily however, and can show honeycomb weathering. This rock has also been exported, and was used in the construction of the government palace of Corfu.[4] The Maltese Lower Globigerina Limestone has been designated by the International Union of Geological Sciences as a Global Heritage Stone Resource.[7]
.
Blue Clay Formation
The Blue Clay (Maltese: Tafal) is a blue-gray mudstone of Langhian to Tortonian in age (~15–10 million years old) measuring up to 65 m thick. It shows major thickness variations and is missing completely from most of the eastern parts of the islands.[1] It was deposited in a deepwater environment. It forms an impermeable layer beneath the Greensand and Upper Coralline Limestone formations. It is most visible in the northwest of Malta and the northeast of Gozo. It allows the capture of rainfall and the creation of aquifers. Water is extracted through wells or escapes through occasional springs when the topsoil has been eroded.[8]
Greensand Formation
The Greensand (Maltese: Ġebla s-Safra) is a glauconite-bearing sandstone of Tortonian age (~10–7 million years old).[1] Yellow-green in colour, it takes on an orange tint when it comes into contact with the air. It is generally very thin, a few tens of centimetres in most areas, with a maximum thickness of 11 m. It is friable and therefore unsuitable for building purposes. Its permeable nature and its position immediately above the Blue Clay allow for the infiltration of rainwater.
Upper Coralline Limestone Formation
The top layer, the Upper Coralline Limestone (Maltese: Qawwi ta' Fuq), is the youngest formation of Messinian age (~7–5 million years old) and is around 140 m thick.[1] It is mainly present on the islands of Malta, Comino and in the east of Gozo. The Coralline Limestone is a hard, pale-grey limestone. It was used frequently in constructions requiring great strength, and in fortifications in particular.
Faults
The rock layers in Malta are relatively flat-lying, with the exception of zones where the rock has been folded close to faults. The faults have two main orientations, with the largest faults being northwest-southeast trending, parallel to the line of islands, although these faults are only locally exposed, and a second set that are WSW-ENE trending, with generally small displacements that dominate the topography of the islands. The largest of the second set are the Victoria Lines Fault on northern Malta and the Qala Fault on southern Gozo. The fault is around 18.5 kilometres (11.5 mi) long.[1][8]
Overall, the islands of the archipelago are tilted towards the northeast, with cliffs on the southwest coast and descending gradients towards the northeast.
Recent geological history
The Maltese archipelago is linked to Sicily by an
References
- ^ a b c d e f g h Continental Shelf Department. "Geological Map of the Maltese Islands". Government of Malta. Retrieved 2018-02-22.
- ^ Galea, P. pp.725–740
- ^ Catalano, R.
- ^ a b Samut Tagliaferro, John
- ^ Sultana, J., et al.
- ^ S2CID 131447222.
- ^ "Designation of GHSR". IUGS Subcommission: Heritage Stones. Retrieved 24 February 2019.
- ^ a b Blouet, B.
- ^ Courtin, J.
- Blouet, Brian (1989). The Story of Malta. Progress Press Publication.
- Catalano, Raimondo. "CENNI SUL MEDITERRANEO MARINO". Siripro (in Italian). Retrieved 26 January 2015.
- Courtin, Jean (1995). "Malte préhistorique, une île de Pâques méditerranéenne?". In Villain-Gandossi, Christiane (ed.). Le Carrefour Maltais. Edisud. ISBN 2-85744-801-5.
- Galea, Pauline (2007). Seismic history of the Maltese islands and considerations on seismic risk. Vol. 50. pp. 725–740.
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ignored (help) - Samut Tagliaferro, John (1991). Malta, its Archeology and History. Casa Editrice Perseus. ISBN 978-8872807040.
- Sultana, Joe; Falzon, Victor. Wildlife of the Maltese Islands. Environment Protection Department.