Tracking Waterways

Tracking Waterways by Shelley Wachsmann It’s what you don’t see that’s important! t is said that the one constant in the universe is change. Everything changes— including the earth. Mountains are being worn down constantly by erosion, and low-lying areas keep filling up with sediment—natural materials worn down by wind and rain that are deposited and then build up, layer upon layer. Variations in weather patterns, as well as human activity itself, cause changes in plant and animal life. These, in turn, affect the topography, or the shape and features, of the earth itself. I Spartans were able to stop the Persian advance because they held a narrow pass, one bounded by mountains on one side and by the sea on the other. But, if you visit Thermopylae today, you will have difficulty understanding the problem encountered by the Persians. Why? —Because there was a change in the topography of the area. Today, the sea is gone, having been filled up and replaced by a vast expanse of land formed by eroding sediment washed down over the millennia from the surrounding countryside. An Impossible Feat Today The Sea Beckoned It is important to keep these facts in mind when dealing with archaeological sites. The look of a site today may be very different from the way that same site appeared in antiquity. Thermopylae in Greece is an excellent example of such changes. It was there that, in 480 B.C., 300 Spartans and their allies held off the entire Persian army in one of the best-known land battles in antiquity. The Now, let me give you another example, from a site on which I worked: The ancient Phoenicians called the lands along the Mediterranean coasts of modern Lebanon and Syria home. However, beginning more than 4,000 (!) years ago, the Phoenicians began taking to the sea, becoming some of the most accomplished traders and seafarers in antiquity. In search of new markets, they Portugal’s coastline at Nazare today 22 dig www.digonsite.com literally “stretched” the ancient world. And, along the way, they founded colonies. The most famous of these was the great city of Carthage, located along the coast of modern Tunisia. The Phoenicians also settled alongside local populations. The Phoenicians crossed the entire Mediterranean and then just kept on going past the Straits of Gibraltar, known in antiquity as the “Pillars of Hercules.” From there, they sailed out into the Atlantic Ocean, voyaging south along the coast of modern Morocco and north along the Portuguese coast. In Portugal, the Phoenicians settled in a number of local settlements where they traded with the local www.digonsite.com people, mainly for the valuable metal resources that were found in this region. You would think that the Phoenicians would have wanted to settle in locations that would give them easy access to the ocean via the great river valleys that cut through Portugal as they flow down to the ocean. Yet, some of the sites where the Phoenicians settled are now located far from rivers, in valleys that are now covered with scrub land and rice paddies. Answers Needed Why would the Phoenicians have chosen to settle in locations that they could not approach with their ships? I suspected that they actually dig 23 Dr. Dig says: could navigate to these settlements and that the river valleys had filled up over time. To test my thinking, I organized a research team. Our goal was to examine sites with Phoenician remains now located in three river valleys: Santa Olaia by the Mondego River, Abul by the Sadu River, and Castro Marim by the Guadiana River. In all three sites, we found evidence that in Phoenician times— beginning more than 2,500 years ago—these sites would have been directly adjacent Dr. Dig says: The job of a geoarchaeologist is to make sense of geology in relation to archaeological sites. A geological hand auger is a hollow tool that is used for boring holes into sediment. It has a sharp end for cutting, rather like a cookie cutter. to their neighboring rivers. How did we do this? We used two methods. The first was geological coring. My colleague, geoarchaeologist Rick Dunn used a sectioned, hand-powered push auger to drill down into the ground. As the auger went deeper, it cut through the various layers of sediment and fill. When Rick pulled the auger out of the ground, it revealed a long core that allowed him to reconstruct the order, depth, and thickness of the various levels. Each layer told a different tale. In most cases, they indicated that the river valleys had silted up gradually. Other levels told of human activity. For example, changes had occurred in recent times that were the result of the land being leveled for rice and salt production. Rick carried out many corings around each of the sites and used radiocarbon tests to date some of the organic materials found in the various levels. Using the information he gathered, Rick was able to create a clear view of the river valleys’ geological changes over time in the vicinity of the ancient sites. Two other colleagues, geophysicists Lawrence Conyers and Eileen Ernenwein, then used ground-penetrating radar (GPR) in some situations and electromagnetic induction (EM) in others. GPR worked well for dry environments, while EM worked best in water-saturated environments. We did encounter problems. Some areas that we needed to survey were located inside flooded rice paddies. At first, Larry and Eileen walked back and forth across the rice paddies carrying the EM device, but we quickly developed a new system, one that used an inflatable kayak that we pulled back and forth across the rice fields. Shelley Wachsmann is the Meadows Professor of Biblical Archaeology in Texas A&M University’s Nautical Archaeology Program. Dr. Dig says: Portugal Careful observation of the terrain revealed an ancient anchor. Geophysicists use various tools to look into the ground, much like the x-ray machine that your doctor uses to see into your body when necessary. The arrow marks the remains of a stone floor or landing uncovered in Abul. The kilns found at the lower end of either side of the floor date to the Roman period. Using electromagnetic induction (EM) to “read” rice paddies A bulldozer helps with digging a trench. 24 dig www.digonsite.com www.digonsite.com dig 25