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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

Geophysical study finds evidence of “labyrinth” buried beneath Mitla

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A geophysical study has found underground structures and tunnels beneath Mitla – The Zapotec “Place of the Dead”

Mitla is an archaeological site associated with the Zapotec culture, located in the Oaxaca Valley in the present-day state of Oaxaca in southern Mexico.

The Zapotec civilisation emerged in the late 6th century BC, originating in the Central Valleys of the Etla. The culture was centred on the settlements of Oaxaca, San José Mogote, and Mitla, with the city of Monte Albán serving as the civic-ceremonial centre.

At its peak, the Zapotec had a population of more than 500,000 inhabitants, having developed sophisticated construction techniques, a writing system, two calendar systems, and complex agricultural cultivation.

In 2016, the Lyobaa Project, an institutional collaboration led by the National Institute of History and Anthropology (INAH) employed ground penetrating radar (GPR), electrical resistivity tomography (ERT), and ambient seismic noise interferometry (AIRSA) to explore potential archaeological features beneath the San Pablo Apóstol church, built atop the Zapotec ruins in Mitla.

Image Credit : Lyobaa Project

According to local legend, the church was constructed on an entrance way to an underground labyrinth, serving as a passage between the realm of the living to the realm of the dead, referred to as Mictlán in Nahuatl, meaning the “place of the dead” or “underworld.”

In 1674, the Dominican chronicler, Francisco Burgoa, described Spanish missionaries entering the labyrinth: “Such was the corruption and bad smell, the dampness of the floor, and a cold wind which extinguished the lights, that at the little distance they had already penetrated, they resolved to come out, and ordered this infernal gate to be thoroughly closed with masonry.”

As part of phase two of the Lyobaa Project, the researchers have identified buried architectural complexes and a series of corridors during a study of the Calvario, Arroyo, and del Sur groups within the archaeological zone.

The Arroyo group, located in the central area of the site has three quadrangle features connected by tunnels that likely date from AD 1200 during the Late Postclassic period.

The project also conducted a survey of the quadrangular plaza where the San Pablo Apóstol church was constructed on the remains of a pre-Hispanic temple. Beneath the plaza the researchers found that there are four mounds with clay internal cores.

Archaeologist, Denisse Argote, said: “We were able to determine that, although the core of the stepped structure is solid, the foundation of the historic church requires short-term intervention to guarantee its conservation, so measures must be taken to ensure its structural stability.”

“There are cracks in the historic building, since it does not have a foundation and, underneath, in what corresponds to the remains of the pre-Hispanic building, it seems that there are areas with small cavities,” added Argote.

Header Image Credit : Shutterstock

Sources : INAH

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

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Archaeology

Discovery of a Romanesque religious structure rewrites history of Frauenchiemsee

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Archaeologists from the Bavarian State Office for Monument Preservation have announced the discovery of a Romanesque religious structure on the island of Frauenchiemsee, the second largest of the three islands in Chiemsee, Germany.

According to the researchers, the structure holds important religious significance, suggesting it might have been erected to venerate Blessed Irmgard (also known as Irmengard), the daughter of King Louis the German and the great-granddaughter of Charlemagne.

During the mid-9th century, Irmgard was appointed the first abbess of Frauenwörth Abbey, who restored the decaying premises and founded a Benedictine convent for nuns. Because of her royal ancestry, she had the right to wear a thin golden hoop resembling a crown, often depicted on paintings and frescoes with her image.

Following her death in 866, Irmgard was venerated and her head reliquary was translated to Seeon Abbey in 1004. She was officially beatified in 1929 by Pope Pius XI, and a celebratory ceremony in 2003 saw her relics reunified.

A recent geophysical study to locate the demolished remains of the Church of Saint Martin has revealed the imprint of a Romanesque structure completely absent from all historical text and contemporary maps.

Image Credit : Bavarian State Office for Monument Preservation

The structure is buried at a depth of 1 metre and measures 19 metres in diameter. The GPR results reveal the floor plan of an octagonal central building with an ambulatory formed by eight supports and four arrange in a cross shape.

Mathias Pfeil of the Bavarian State Office for Monument Preservation notes that religious structures with pre-Romanesque or Romanesque architecture, particularly those with sacral significance, are exceedingly uncommon north of the Alps. Such edifices are often perceived as imitations of the Church of the Holy Sepulchre in Jerusalem.

According to the researchers, the structure was likely built during the construction of the new monastery and Romanesque abbey church (of which the gatehouse and bell tower survive to this day) to venerate Irmgard as a destination for pilgrims

Header Image Credit : Bavarian State Office for Monument Preservation

Sources : Bavarian State Office for Monument Preservation

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

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