WORLD

Thanks to satellite imagery, archaeologists have uncovered nearly 400 ancient, previously undocumented stone structures in the Arabian desert. (New York Times)

How do scientists identify ancient structures with satellite imagery? Our own “space archaeologist” can help answer that!

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

Discussion Ideas

• Huge, ancient stone structures were just discovered in the Arabian Desert. How did they hide in plain sight for thousands of years?
  • landscape. The deserts of Saudi Arabia are forbidding and still largely uninhabited.
  • technology. The overall structure of the stone walls is only apparent from an aerial viewpoint—a plane, drone, or satellite. Although similar structures have been studied in nearby Jordan, Saudi Arabia has traditionally been hesitant to allow planes to fly in its airspace.
  • lack of access. The structures were first discovered and identified not by archaeologists at all, but by citizen scientists! The Desert Team is a group of enthusiastic “amateur Saudi travelers and researchers who are interested in Arabian desert and its history, geography, and archeology.”
    • Whether they know it or not, the Desert Team engaged in a great Nat Geo-Inquiry question: “The question we always discuss while investigating them is, why here? Why in this stony, frightful, rugged land?”
    • The Desert Team reported their discoveries to archaeologists, who responded with “absolute bafflement.”

• Archaeologists report that the stone structures were discovered in a “harrat.” What is a harrat?
  • A harrat describes an ancient lava plain. Rocky harrats spill across the Middle East.
    • The harrat associated with the newly discovered stone structures is Harrat Ash Shamah, which stretches about 25,200 square kilometers (5,869 square miles) between Jordan and Saudi Arabia.
      • Yes, the volcano was probably active during the construction of at least some of the structures. The “structures are all associated with old lava domes, now inactive, but were active during construction of these stone gates. The volcanic domes ejected basaltic lava, which flowed down the sides of the dome creating large lava fields.”

• Why do archaeologists call the rectangular structures “gates”?
  • Well, they look like field gates. “[W]hen looked at horizontally, they resemble a simple fence with two thick upright posts on the sides connected by one or more long bars.” Take a look at a field gate here. Remember: The stone structures are not actually gates!
    • The gates range from a hundred meters (several hundred feet) to nearly 490 meters (1,600 feet) in length. The end sections are as thick as 9 meters (30 feet).

• What are the gates made of?
  • They’re carefully piled rocks. The rocks are basaltic lava, common in the harrat.

• What were the gates used for?
  • No idea! This is a true archaeological mystery. Scientists have some ideas of what the gates were probably not used for:
    • not pens or animal traps. The gates do not resemble previously identified “kites”, which ancient cultures used to corral and pen animals. (Guess what the “kites” look like …)
    • not dwellings. The gates do not look like houses or temples. They’re enormous, with no obvious “doors” or points of entry.
    • not necropolises. Archaeologists are very, very familiar with burials, funerary structures, and “cities of the dead.” The gates don’t look like they were used for disposing of dead bodies.

• Who built the gates?
  • We really don’t know, although archaeologists studying the sites think they may be ancestors of today’s Bedouin communities.
  • Scientists think the builders were likely nomadic, tribal communities active in the area during the late Neolithic and Bronze Age, between 2,000 and 9,000 years ago.
    • When studying history, it’s always fun to put events in perspective:
      • about 9,000 years ago: Communities began to permanently settle the cities we now know as Aleppo, Syria, and Amman, Jordan.
      • about 7,000 years ago: The wheel was invented, probably in Mesopotamia.
      • about 6,000 years ago: People in Northern China developed what many consider the first proto-writing system.
      • about 5,500 years ago: Egyptians began to mummify their dead.
      • about 4,500 years ago: The Maya civilization began to develop in Central America.
      • about 2,800 years ago: Ancient Greeks composed the Iliad and the Odyssey.
      • about 2,500 years ago: The Buddha was born in India.
      • about 2,000 years ago: The Roman Empire was established under Julius Caesar.

• Many archaeologists consider the Saudi gates to be geoglyphs. What are geoglyphs? Use our fun study guide for some help.
  • A geoglyph is a large design (glyph) produced on the ground from earthen (geo-) materials, such as dirt and rocks.
    • The Saudi gates are positive geoglyphs. This means their creators used earthen materials to build up the glyph. Negative geoglyphs are produced by removing earthen materials to carve channels or canals.

• Where else on Earth can you find geoglyphs?
  • All over!
    • The most famous geoglyphs in the world are probably the lovely Nazca Lines in Peru. The Nazca Lines, which include both positive and negative geoglyphs, were created between 500 BCE and 500 CE.
    • The Uffington White Horse is a negative geoglyph cut into the white chalk hills of Oxfordshire, England. The beautiful Uffington White Horse was created between 1000 BCE and 700 CE.
    • Native Americans in what is now Effigy Mounds National Monument, Iowa, created enormous positive geoglyphs in the shape of bears, birds, turtles, and panthers. The moundbuilding cultures associated with the geoglyphs of Iowa and Wisconsin flourished between 615 and 1250.
    • The Turgai geoglyphs of Kazakhstan are complex geometric designs possibly used to track the movements of the sun more between 1,000 and 9,000 years ago.
    • Deforestation has revealed positive geoglyphs in the Amazon basin. These pre-Columbian geoglyphs were created between 1,000 and 2,000 years ago.
    • A giant elk simply known as the “Russian geoglyph” was discovered in the meteor-prone Chelyabinsk region 2011. The positive Russian geoglyph was created between 4000 BCE and 2000 BCE.
    • The Blythe intaglios of people and animals are part of the desert landscape near my hometown of Blythe, California. The negative geoglyphs were created between 900 BCE and 1200 CE.

• Where else has satellite imagery helped archaeologists discover ancient structures?
  • Our own “space archaeologist,” Sarah Parcak, has identified the ancient Egyptian city of Tanis and potential sites of pyramids using satellite imagery.
  • The Turgai geoglyphs in Kazakhstan were first identified using NASA satellite imagery.
  • Archaeologists identified Maya ruins in Guatemala using NASA satellite imagery.
  • Citizen scientists using Google Earth imagery helped identify the remains of an ancient Roman villa near Parma, Italy.
  • Students and citizen scientists used Google Earth to identify an 800-year-old fortress in Afghanistan.

TEACHERS TOOLKIT

New York Times: Hundreds of Mysterious Stone ‘Gates’ Found in Saudi Arabia’s Desert

Forbes: 400 Mysterious Stone ‘Gates’ Discovered In Remote Saudi Arabia

Google Earth: Zoom in on Saudi “Gates”

Nat Geo: Space Archaeology