Mai
Samih listens to the story of civilisation in Egypt from a geological
perspective.
Rocks
and earth layers have as much to say as a drawing on a temple about the past,
maybe even more. Head of the Department of Geology and professor of
Geo-Archaeology at the Faculty of Science at Cairo University Mohamed
Abdel-Rahman Hemdan said as much at a seminar at Beit Al-Sinary in Cairo in
March when he claimed that “the past is the key to the present.”
“We
geologists study the present to understand what happened in the past. However,
that past is also the key to the present because archeologists have learned
much about how the climate in particular has changed over time. This is a new
trend we are now trying to work with,” he said.
The
climate is the weather over the long term, Hemdan said, commenting that
time-scales of 100 to a million years are not uncommon in geology. Cold weather
in the north could affect the surface of the oceans and the winds in another
part of the planet that carry rain.
“Rain
for us in Egypt originates from two sources, the Atlantic monsoon from the west
and the Indian monsoon from the east. These unite into one front named the
Intertropical Convergence Zone (ITCZ), which causes rain. If this is directed
northwards, it leads to rain, as happened some 11,000 to 8,000 years Before the
Present (BP). If it goes southwards, a state of drought occurs. This could be
good news for those who fear global warming, as when the sea level rises our
desert will become green because there will be more rain,” he said.
Some
150,000 years BP the sea level was low, and the weather in Ethiopia was not as
wet as it is today, so it did not feed a lot of water into the Nile. The River
Nile looked like a small channel at the time, and the water level in the
Mediterranean was 120 metres lower than it is today.
“Approximately
25,000 to 11,000 years BP there was a dry era called the Last Glacial Maximum
(LGM), and Egypt went through a drought. In cool weather, the sea level decreases.
The Nile flood level was low, and because of the low sea level the Delta had
more branches that started to multiply and deepen. These left what are
sometimes called ‘turtle backs’ behind them, sediments of soil that people
would settle on to be higher than the water level during floods,” Hemdan
said.
This
period was followed by wet conditions. “From 11,000 to 8,000 years BP, the Nile
flood was very high, and the desert also saw a lot of rain, meaning that
scientists called it the ‘Green Sahara’ era,” he said, adding that human beings
were free to live more widely as a result.
From
10,000 to 8,000 years BP, the land was once again very wet, and the River Nile
would increase one cm every year. There was a lot of rain in Ethiopia, and the
water in the Nile turned the flood plains into swamps. The river did not
deposit much sediment, and it would flood the valley all year round, Hemdan
added.
“Some
2,000 years BP is a very important era for the whole planet as it was an ice
age that lasted for about 1,000 to 1,500 years, also affecting Egypt,” he said,
adding that the Nile at that time consisted of two channels, the main one and
one that resembled the Bahr Al- Lebeni and Giza channels that can still be seen
today. “We discovered this through satellite images. The first was a short,
thin channel near the desert during the Pre-Dynastic Period, and the second one
was a large one in the current Nile channel,” he said.... READ MORE.
