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The Eye of the Sahara

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The Eye of the Sahara, also known as the Richat Structure and the Eye of Africa, is a geological feature in the Sahara Desert’s Adrar Plateau, located in west–central Islamic Republic of Mauritania.

The structure is an eroded elliptical dome of sedimentary rock, that ranges in age from the Proterozoic (2500 to 538.8 million years ago) within the centre, to Ordovician (488.3 to 443.7 million years ago) sandstone around its periphery.

The dome has a diameter of 40 kilometres (25 mi), with an interior comprised of intrusive and extrusive igneous rocks, including rhyolitic volcanic rocks, gabbros, carbonatites and kimberlites.

The rhyolitic rocks have been interpreted as lava flows that are part of two distinct eruptive centres formed from the remains of two maars, a low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion caused when groundwater comes into contact with hot lava or magma).

Eye of the Sahara – Image Credit : NASA – Public Domain

The gabbroic rocks form two concentric ring dikes, the inner ring dyke is 20 metres in width and lies 3 kilometres from the centre of the structure, while the outer ring dyke is 50 metres in width and is located 7 to 8 kilometres from the centre.

The processes that formed the structure has been theorised to be the result of either a meteoric impact, or a deep magmatic intrusion, the latter of which is supported with high-resolution airborne magnetic data and gravity data to reinforce the intrusion hypothesis.

The Eye of the Sahara was first identified during the 1950’s from aerial photographs, leading to ongoing studies by geologists until as recently as 2008. This latest study, explained that the ridges and valleys we see today are formed by the differential erosion of alternating hard and soft rock layers, uplifted as a dome by an underlying alkaline igneous complex of the Cretaceous age.

Archaeological research at the structure has revealed evidence of human activity, with numerous deposits of pre-Acheulian and Acheulian artefacts, characterised by the distinctive oval and pear-shaped “hand axes” normally associated with Homo erectus and derived species such as Homo heidelbergensis.

Acheulean tools were produced during the Lower Palaeolithic era across Africa and much of West Asia, South Asia, East Asia and Europe, first developed about 1.76 million years ago and derived from the more primitive Oldowan technology associated with Homo habilis.

Research by archaeologists have found Acheulean sites located along wadis that occupy the outermost annular depression of the structure, where outcrops of quartzite were sourced to provide the raw materials for tool manufacturing. Tool types found in Acheulean assemblages include pointed, cordate, ovate, ficron, and bout-coupé hand-axes (referring to the shapes of the final tool), cleavers, retouched flakes, scrapers, and segmental chopping tools.

The geographic distribution of Acheulean tools – and thus the peoples who made them – is often interpreted as being the result of palaeo-climatic and ecological factors, such as glaciation and the desertification of the Sahara Desert.

The climate of the region has undergone enormous variations between wet and dry periods over the last few hundred thousand years, believed to be caused by long-term changes in the North African climate cycle that alters the path of the North African Monsoon.

During the African humid period (AHP), much of the Sahara desert was covered by grasses, trees and lakes, where the people of the Lower Palaeolithic lived an existence as hunter-gatherers.

Evidence of Neolithic activity has also been found, with sparse, widely scattered spear points and other artefacts located northwest of the outer ring, although generally absent in its innermost depressions of the structure.

Due to the lack of middens or identifiable evidence of sustained occupation, this has led to the interpretation that the structure was only used for short-term hunting and stone tool manufacturing.

A pseudo theory by Fractal Source Research (FSR), proposes that the structure is the remnants of an advanced Antediluvian civilisation, namely the lost city of Atlantis, based on a comparison of measurements from the structure with the descriptions given by Plato.

Eye of the Sahara, taken by the Sentinel-2 Satellite – CC BY-SA 3.0 IGO

 

This content was originally published on www.heritagedaily.com – © 2023 – HeritageDaily

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Archaeology

Monastic site founded by St Moulag discovered on Scottish island

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Archaeologists from the Lismore Historical Society have announced the discovery of a stone built monastic site on the Hebridean Isle of Lismore.

According to the researchers, the site dates from the 7th to 10th century AD and was likely founded by St Moluag, an Irish missionary who evangelized the Picts on the western seaboard of Scotland.

Lismore had long been an important religious centre for the Gaelic kingdom of Dalriada, which likely motivated the decision to found a monastic community in AD 562. Irish missionaries had learnt to focus heavily on the similarity and continuity between early Christianity and Paganism rather than the differences between them.

However, according to tradition, the rock on which Moluag stood detached itself from the Irish coast and he drifted across to the island of the Lyn of Lorn in Argyll, now called the Isle of Lismore in Loch Linnhe.

Following a six year community led project on the island, members from the Lismore Historical Society have uncovered an oval stone building and a workshop where craft workers manufactured jewellery from precious metals.

Part of a crucible – Image Credit : Lismore Historical Society

Radiocarbon dating has placed the building to the 7th-10th century AD during the period of the early monastery.

The study has so far discovered fragments of around 120 crucibles, broken ceramic moulds for making penannular brooches, and carvings made in stone, wood, bone and antler.

According to a press statement by the Lismore Historical Society: “XRF analysis of the surfaces of these crucibles at the National Museum of Scotland has revealed that they were used for melting copper-alloys, silver and gold.

This fine craft activity is evidence of a sophisticated and influential monastic centre, the society said, with analysis and conservation of 1500 significant finds from the site ongoing.

Header Image Credit : Lismore Historical Society

Sources : Lismore Historical Society

This content was originally published on www.heritagedaily.com – © 2023 – HeritageDaily

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Archaeology

Inrap archaeologists uncover medieval castle beneath French hotel

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Excavations at the Château Lagorce, a former 18th century private mansion in Vannes has revealed traces of the town’s medieval castle.

Vannes is located in the Morbihan department of Brittany in north-western France. In medieval times, the town served as the centre of a principality or kingdom recognised as Bro-Wened (“Vannes”) or Bro-Ereg (“land of Gwereg”).

Recent excavations by archaeologists from the National Institute for Preventive Archaeological Research (Inrap) have found traces of the towns medieval castle in preparation for the development of a fine arts museum.

As part of the first phase of excavations, the researchers have conducted a study of the mansion’s courtyard where they uncovered two stories of the castle’s defensive wall and a moat, located at a depth of 13 feet beneath street level.

The castle was built around 1380 by Jean IV who held the titles of Duke of Brittany and Count of Montfort from 1345, and the 7th Earl of Richmond from 1372. Known as the Château de l’Hermine (Castle of Hermine), the castle was constructed to assert the Duke’s central authority over his duchy and the town of Vannes.

Image Credit : Emmanuelle Collado, Inrap

According to Inrap, the surviving stonework suggests that the castle had three to four floors and several staircases, one of which has been described as “remarkably preserved”. The team also found markings on several worked stones that the workers used to follow a building, and architectural features such as the latrines and drainage pipes.

A search of the latrines has also revealed traces of castle life from the 15th and 16th centuries, including coins, knives, tiles, wooden bowls, kitchen utilities, and several pieces of jewellery. Due to the conditions of the soil, objects such as items of clothing, shoe buckles, pins, rings, and a ball padlock have also survived.

Excavations have also uncovered a mill connected to the residential part of the castle, where a large water well was powered by water passing through a canal, and remnants of a bridge that connected the castle to the town.

Header Image Credit : Emmanuelle Collado, Inrap

Sources : Inrap

This content was originally published on www.heritagedaily.com – © 2023 – HeritageDaily

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