Case solved! Scientists solve the mystery of pyramid construction: how the huge stones were transported

The Step Pyramid of Djoser, built during the Third Dynasty. Image courtesy of Eman Ghoneim

Today, this tributary of the Nile River, buried under the rolling yellow sands of the Sahara Desert, may be able to reveal the mystery of the construction of the ancient Egyptian pyramids.

In Egypt's Western Desert, on a rocky, arid plateau stands the Great Pyramid of Giza , known as one of the "Seven Wonders of the Ancient World." For years, scientists have been studying this 140-meter-tall stone building, as well as several smaller pyramids in the area. They are committed to deciphering ancient Egyptian inscriptions in the hope of revealing how the ancient Egyptians built such huge structures and trying to understand why they built the pyramids so far away from the lifeblood of their civilization, the Nile River.

Eman Ghoneim, a professor of geomorphology at the University of North Carolina at Wilmington, said she has been pondering this ultimate mystery of ancient Egypt for several years. "I was born and raised in Egypt and have spent most of my life here," she said. "From a very young age, I have been thinking about this question: 'Why did our ancestors build pyramids in this strange place specifically? Why so far away from water? ' I have a hunch that there is more to discover here."

Eman Ghoneim studies the topography of the ancient Ahramat tributary located in front of the Pyramids of Giza and the Great Sphinx. Image courtesy of Eman Ghoneim

Recently, Ghoneim discovered that the pyramids were actually built very close to a river (today, their closest watercourse to the Nile is more than 8 kilometers away). She and her team analyzed a large number of satellite images and collected sediment samples from deep underground in the desert, from which they found a long-lost tributary of the Nile River. This tributary once flowed through the foothills of the western desert plateau, very close to the pyramid area.

Gunem said they named this tributary "Ahramat" (Ahramat, meaning "pyramid" in Arabic), and the builders of the pyramids may have used this tributary to transport building materials . Knowing the direction of this tributary can help archaeologists find possible settlements of ancient Egyptians, which are now buried under the vast dusty plains. The relevant paper has been published in the journal Communications Earth & Environment.

Scientists have long suspected that the Nile once had multiple tributaries . The main stream of the Nile originates from Lake Victoria in Tanzania, Kenya and Uganda, stretches northward for about 6,600 kilometers, and flows into the Mediterranean Sea. Past studies have shown that during the middle Holocene (about 10,000 to 6,000 years ago), the Nile floodplain was a lush wetland, but by the late Holocene, long-term rainfall shortages and severe droughts caused it to gradually shrink and become barren.

The Red Pyramid of the Dahshur necropolis, built during the Fourth Dynasty. Image via Eman Ghoneim

Today, the Sahara Desert is scorching and unforgiving, making any field work here extremely difficult , including finding the former river course. Before bravely facing the field work, the research team first used scanning images from radar satellites to search for hidden traces beneath the surface.

In these photos, you can see subtle patterns and textures in the strata near the pyramids - these features are different from other areas of the desert and may represent rivers. "We need to observe subtle natural features in the area around the pyramids, such as a long depression or groove, but these structures are now completely covered by farmland and desert. If you don't know what you are looking for, it is difficult to find them," said Ghoneim.

After confirming the satellite images, Ghoneim and her colleagues traveled to Egypt and used a large drill to dig two sets of "cores," or cylindrical sediment samples. When the drill pulled out sand from deep underground, Ghoneim knew they had found a lost river. "Of course there is sand on the surface," she said, "but if you find sand and other coarse-grained sediments underground, rather than clay or silt, that means there was water flowing there."

The research team sorted out the soil samples they collected. Image courtesy of Eman Ghoneim

The researchers traced the former course of the Ahramat River and found that the tributary was nearly 60 kilometers long. Gunem said the river could be longer and further research is needed to determine its overall depth and width. The reason why this tributary dried up is still unclear , but the research team speculates that the movement of tectonic plates, the accumulation of wind-blown sand, and the severe drought in the late Holocene led to its demise.

The watercourse of the ancient Ahramat tributary is adjacent to a large number of pyramids dating from the Old Kingdom to the Second Intermediate Period, spanning the Third Dynasty to the Thirteenth Dynasty. Image from the paper

Dev Niyogi, a professor of geology at the State University of Texas at Austin who was not involved in the study, said that understanding how changing landscapes and river courses shaped ancient societies could help guide modern people in building infrastructure more appropriately in the context of today's climate change .

The ancient Nile's tributaries are also a reminder that "capable human societies are never rigid," said Adam Rabinowitz, an archaeologist and professor of classics at the school, who is working on a project to help Texans prepare for the dramatic changes in the state's water supply due to climate change over the next 25 years. "We need to explore how past societies responded to similar climate challenges and learn from them how humans can face and adapt to major environmental changes."

Next, Ghoneim hopes to piece together a picture of life along the Nile by further studying Ahramat and other waterways that have disappeared into the desert. “For most cities, we’re not talking about the role of water in building the pyramids, but about how human civilizations depended on water and adapted to changes in waterways,” she said. “We learn from the past so we can prepare for the future.”

References

[1]https://www.scientificamerican.com/article/egypts-famed-pyramids-overlooked-a-long-lost-branch-of-the-nile/

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Source: Global Science (ID: huanqiukexue)

Author | Riis Williams

Translation | Wei Shuhao

Editor: He Tong

Proofread by Xu Lai and Lin Lin

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