A couple weeks ago we traveled south to visit the new museum in Ghor es-Safi, the “lowest place on earth.” It is being put together by our friend and fellow ACOR fellow, Constantinos (Dino) Politis. He has excavated in this area for the last 20 or so years, including excavating Lot’s Cave. As you travel south along the Dead Sea there are massive cliffs next to the road. These cliffs are exposed on either side of the Jordan Valley, which is part of the greater Rift Valley running from Syria south through much of Africa.
Layer upon geological layer is visible as you drive, however down in the Ghor, Dino pointed out a place where five different geological formations can be seen (see picture above). As a lover of historical geography I thought this was a fantastic teaching picture. These are formations that emerge in different parts of Israel and Jordan and play an important part in understanding the historical geography of the region.
- Located at the top is Cenomanian/Turonian limestone. Located throughout the hill country on either side of the valley this limestone is very hard and is used as building material. It also contains aquifers so springs pop up along its seams where the formation has been exposed.
- Below this layer is the undulating red of the Kurnub and Nubian Sandstone. In Jordan these layers are exposed along the major wadi systems and are especially prevalent in the area around Petra.
- Rising through the sandstone layer is a black volcanic plug. This igneous rock is Precambrian in date and appears in small pockets along the Jordan Valley.
- Below all these geological formations (and located just above the houses in the picture) is marl dating to the Pleistocene/Pliocene periods. This marl is exposed all along the Jordan Valley floor. It is a calcium carbonate and is generally found where ancient freshwater lakes once were located.
- Lastly, all the way at the bottom, is alluvium, fertile soil deposited by the various wadis running into the Valley.