Archaeologists map the submerged landscape around Grado
A team of archaeologists from the University of Udine have mapped the submerged landscape between the sea of Grado and Roman Aquileia.
The study project, named Aquileia Waterscape, is reconstructing the archaeological features on the outskirts of the Roman city, which was founded in 181 BC along the Natiso River in the present-day Friuli-Venezia Giulia region, Italy.
The colony functioned as a strategic frontier fortress in the northeastern corner of Transpadane Italy, and was established to safeguard the Veneti, loyal allies of Rome during both Hannibal’s invasion in the Second Punic War and the Illyrian Wars.
The waters around Grado were part of the city’s extensive port system, facilitating the movement of goods between large seafaring vessels and smaller, flat-bottomed boats that could access the urban port.
The identification of underwater features first begun in 2019, when sonar detected traces of an anchor stump. This led to the discovery of two new Roman wrecks (Grado 5 and Grado 6) during a campaign in 2022.
According to a press statement issued by the University of Udine, archaeologists used a Global Navigation Satellite System (GNSS) for precise positioning, side-scan sonar, and photogrammetric surveys.
Seven underwater sites have been identified, including shipwrecks, a Roman funerary altar, and several monumental structures.
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The most significant site is the so-called Piere di San Gottardo, located 1.5 kilometres to the south-east of the entrance to the Grado lagoon.
The site features a quadrangular arrangement of stone blocks resting on a sandy seabed at depths ranging from 3.9 to 4.4 metres, rising up to a height of 2 metres beneath the surface. The survey at Piere di San Gottardo also found funerary monuments, including an undocumented funerary altar, and linear architectural elements.
Mantle plume mechanics underneath Easter Island. Credit: Douwe van Hinsbergen
Geography textbooks describe the Earth's mantle beneath its plates as a well-mixed viscous rock that moves along with those plates like a conveyor belt. But that idea, first set out some 100 years ago, is surprisingly difficult to prove. A mysterious find on Easter Island, investigated by Cuban, Colombian and Utrecht geologists among others, suggests that the Earth's mantle seems to behave quite differently.
Easter Island consists of several extinct volcanoes. The oldest lava deposits formed some 2.5 million years ago on top of an oceanic plate not much older than the volcanoes themselves. In 2019, a team of Cuban and Colombian geologists left for Easter Island to accurately date the volcanic island.
To do so, they resorted to a tried-and-tested recipe: dating zircon minerals. When magma cools, these minerals crystallize. They contain a bit of uranium, which "turns" into lead through radioactive decay. Their findings are availableas a preprint inESS Open Archive.
Because we know how fast that process happens, we can measure how long ago those minerals formed. The team from Colombia's Universidad de Los Andes, led by Cuban geologist Yamirka Rojas-Agramonte, therefore went in search of those minerals. Rojas-Agramonte, now at the Christian Albrechts-University Kiel, found hundreds of them. But surprisingly, not only from 2.5 million years old, but also from much further back in time, up to 165 million years ago. How could that be?
Chemical analysis of the zircons showed that their composition was more or less the same in all cases. So, they all had to have come from magma of the same composition as that of today's volcanoes. Yet those volcanoes cannot have been active for 165 million years, because the plate below them is not even that old. The only explanation then is that the ancient minerals originated at the source of volcanism, in the Earth's mantle beneath the plate, long before the formation of today's volcanoes. But that presented the team with yet another conundrum.
Hotspot volcanoes and their origins
Volcanoes like those on Easter Island are so-called "hotspot volcanoes." These are common in the Pacific Ocean; Hawai'i is a famous example. They form from large blobs of rock that slowly rise from the deep Earth's mantle—so-called mantle plumes. When they get close to the base of the Earth's plates, the rocks of the plume as well as from the surrounding mantle melt and form volcanoes.
Scientists have known since the 1960s that mantle plumes stay in place for a very long time while the Earth's plates move over them. Every time the plate shifts a bit, the mantle plume produces a new volcano. This explains the rows of extinct underwater volcanoes in the Pacific Ocean, with one or a few active ones at the end. Had the team found evidence that the mantle plume under Easter Island has been active for 165 million years?
Statues on Easter Island. Credit: Douwe van Hinsbergen
Subduction zones
To answer that question, Rojas-Agramonte needed evidence from the geology of the "Ring of Fire," an area around the ocean with many earthquakes and volcanism, where oceanic plates dip ("subduct") into the Earth's mantle. So she contacted Utrecht geologist Douwe van Hinsbergen.
"The difficulty is that the plates from 165 million years ago have long since disappeared in thosesubduction zones," says Van Hinsbergen, who had reconstructed the vanished pieces in detail. When he added a large volcanic plateau to those reconstructions at the site of present-day Easter Island 165 million years ago, it turned out that that plateau must have disappeared under the Antarctic Peninsula some 110 million years ago.
"And that just so happened to coincide with a poorly understood phase of mountain building and crust deformation in that exact spot. That mountain range, whose traces are still clearly visible, could well be the effect of subduction of a volcanic plateau that formed 165 million years ago," he adds.
His reconstruction therefore showed that the Easter Island mantle plumecould very well have been active for that long. This would solve the geological mystery of Easter Island: the ancient zircon minerals would be remnants of earlier magmas that were brought to the surface from deep inside the earth, along with younger magmas in volcanic eruptions.
Inconsistencies
But then another problem presents itself. The classical "conveyor belt theory" was already difficult to reconcile with the observation that mantle plumes stay in place while everything around them continues to move. Van Hinsbergen says, "People explained this by saying that plumes rise so fast that they are not affected by a mantle that was moving with the plates. And that new plume material is constantly being supplied under the plate to form new volcanoes."
But in that case, old bits of the plume, with the old zircons, should have been carried off by those mantle currents, away from the location of Easter Island, and could not now be there at the surface.
"From that, we draw the conclusion that those ancient minerals could have been preserved only if the mantle surrounding the plume is basically as stationary as the plume itself," he adds.
The discovery of the ancient minerals on Easter Island therefore suggests that the Earth's mantle behaves fundamentally differently and moves much slower than has always been assumed; a possibility that both Rojas-Agramonte and Van Hinsbergen and their teams raised a few years ago in studies on the Galapagos Islands and New Guinea, and for which Easter Island now provides new clues.
Massive H Shaped Megalithic Structures Carved From Stone Archaeologists Can't Explain
In the Bolivian Andes, a mind-boggling discovery has stunned archaeologists: massive H-shaped megalithic structures unearthed in the ancient ruins of Puma Punku and Tiwanaku. These colossal stone monuments challenge our understanding of prehistoric engineering. Explore the intricate carvings and precise joints of these megalithic marvels. How did ancient civilizations construct these massive stones without modern technology? Was it forgotten technology or something more extraordinary? Delve into the mysteries of Puma Punku and Tiwanaku. Uncover the secrets of a lost civilization with knowledge beyond its time. Prepare to be amazed by these ancient structures, and question everything you thought you knew about the past.
Elaborate murals from the ancient Moche found at Pañamarca, Peru.Courtesy Archaeological Landscapes of Pañamarca
In September, archaeologists in Peru uncovered an elaborate throne room and hall that they believe could indicate that powerful women ruled more than 1,300 years ago.
The throne room and hall were found at Pañamarca, an archaeological site that was once a religious and political center of the ancient Moche culture. The hall is decorated with elaborate snake murals, and is even complete with a worn throne.
The paintings within the newly discovered chamber show a woman seated on the throne while receiving visitors. There are also depictions of a crown, the crescent moon, sea creatures, and a weaving workshop.
Dating to 650 CE, the throne showed signs of wear on its backrest. A human hair and colorful stones were found embedded in the throne. There are plans to perform a DNA analysis of the hair, though experts remain uncertain whether there is enough material to do so, according to a release the Pañamarca archaeological research program.
Another chamber, dubbed the Hall of the Braided Serpents, was also constructed with wide pillars and overlooked a plaza. It is decorated with paintings of large serpents with human legs, as well as images of warriors and an unidentified mythical creature. The motifs featured here are unlike those that can be seen in previously discovered Moche art, the research program said.
These finds reinforce experts’ consensus that Moche culture was not male-dominated, something that prior finds in the region have also suggested. Because the Moche lacked a formal writing system and many sites were looted since they held power, archaeological finds such as this one are how historians understand this people’s culture.
More could be revealed as archaeologists continue to excavate the site. Work on the main pyramid, for example, has yet to occur.
