Saturday, 4 January 2020


Much of Egypt's history is carved in her rock. We think of Egypt as old, with remarkable human history, but the land that formed this part of the world tells us of a much older time in Earth's past.

Egypt, officially the Arab Republic of Egypt, is a country in the northeast corner of Africa, whose territory in the Sinai Peninsula extends beyond the continental boundary with Asia.

Egypt is bordered by the Gaza Strip (Palestinian territories) and Israel to the northeast, the Gulf of Aqaba and the Red Sea to the east, Sudan to the south, Libya to the west, and the Mediterranean Sea to the north. Across the Gulf of Aqaba lies Jordan, across the Red Sea lies Saudi Arabia, and across the Mediterranean Sea lie Greece, Cyprus and Turkey, although none of these share a land border with Egypt.

Five hundred kilometres southwest of Cairo, the flat sabkha plain stretches in all directions covered by a small layer of dark, round pebbles. There are spectacular limestone pillars dotting the landscape of the wonderful karst topography. This land, once the breadbasket of Egypt and the stomping ground of the Pharaohs, is now ruled by pipelines and rusted-out trucks abandoned as wrecks marking the passage of time. Beneath the sand, rust and human history lie some very interesting geology. This rock has been sculpted both through erosion and at the hands of her craftsmen.

The rock here was formed when the Earth's crust was just beginning to cool, 4 to 2.5 billion years ago, during the Archaean. Other rock dates back to the Proterozoic when the Earth's atmosphere was just beginning to form. The oldest of these are found as inliers in Egypt’s Western Desert. The rocks making up the Eastern Desert are largely late Proterozoic in age, the time when bacteria and marine algae were the principal forms of life.

Throughout the country, this older basement is overlain by Palaeozoic sedimentary rocks. Cretaceous outcrops are common. We also find sediments that tell a story of repeated marine transgression and regressions, sea levels rising and falling, characteristic of the Cenozoic. It is from Egypt's Cenozoic geology that we get the limestones used for the great pyramids.

Limestone and Light: Egypt
The pyramids were built of limestone, granite, basalt, gypsum (mortar), and baked mud bricks. Together they form some of the oldest (and last remaining) wonders of the ancient world. The great pyramids of Giza, with their smooth exteriors carved from fine grain white limestone quarried at Tura on the Giza-plateau, are built from Egypt's much older geologic history.

The limestone from Tura was the finest and whitest of all the Egyptian quarries and chosen for the facing stones for the richest tombs. It is interesting in that it is made up almost entirely of Nummulites. Nummulites are the calcareous chambered shells (tests) of extinct forms of marine, amoeba-like organisms (protozoans) called foraminifera that accumulated in huge quantities during the early Cenozoic. Foraminifera are still alive in the sea today, though none quite as large as Nummulites. For the central chamber, with the sarcophagus of the pharaoh, lovely reddish-pink granite from Aswan was used. The granite helped to take the weight of this massive construction.

Back in 2013, archaeologists made an unlikely find in a cave seven hundred kilometres from Giza. Their find, a 4,600-year-old papyrus scroll, details an ancient shipload of rock, likely destined for  Khufu's pyramid. The papyrus is addressed to Ankh-haf, Khufu’s half-brother, and describes the undertaking of an expedition by a 200-man crew to the limestone quarries near Tura, on the eastern shore of the Nile. After loading the blocks onto their ship, the expedition indented to float down the river Nile for a successful delivery.

The Greek historian Herodotus visited Egypt in the 5th century BC, he described the building of Khufu's pyramid by more than 100,000 slaves. Those slaves then had the unenviable task of unloading the 2-3 ton blocks, then pulling them across ramps to be dragged to the construction site.  It is estimated that 5.5 million tonnes of limestone, 8,000 tonnes of granite (imported from Aswan), and 500,000 tonnes of mortar were used in the construction of the Great Pyramid.