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Discover why the Nile was once deeper than the Grand Canyon!

Construction of the Aswan High Dam began in the summer of 1960. This feat of engineering was intended to tame the world’s longest river.

Even today, the Aswan Dam on the Nile is the largest dam in the world. It regulates river flow, prevents catastrophic floods, supports shipping, generates half of Egypt’s electricity and irrigates hundreds of thousands of acres of agricultural land in Egypt and Sudan.

A massive structure like this requires a solid foundation, so builders drilled through the sand, gravel, and clay sediments in search of bedrock. To their surprise, they discovered that the crystalline granite bedrock was much deeper than anyone had anticipated.

Further analysis and drilling throughout East Africa, up and down the Nile, and in and around the Mediterranean Sea – often with the priority of prospecting for oil – yielded an intriguing conclusion:

Five and a half million years ago, the Nile flowed through a massive canyon the size of Arizona’s present-day Grand Canyon.

The rise of the Ethiopian highlands

The Ethiopian highlands consist of volcanic basalt.

mbrand85/Shutterstock.com

To better understand the geological history of the Nile, let’s throw our thoughts even further back in time – 30 million years ago, when the Nile’s waters first began to flow (according to the latest and best evidence-based models).

Volcanic mantle plumes emerging from the Afar Triple Junction (where three tectonic plates, the Nubian, Somali, and Arabian plates pull away from each other), poured out layer after layer of basaltic lava to form the Ethiopian Highlands.

As rain and meltwater from the highlands flowed down the slopes, streams developed into rivers. One of these rivers flowed downhill all the way north to the salty waters of the Mediterranean, almost 1,500 miles away. And so the course of the Blue Nile took shape.

The drying up of the Mediterranean

Discover why the Nile was once deeper than the Grand - March 19, 2024
Today, the Nile and its delta provide the necessary irrigation in the middle of the African desert, but millions of years ago the landscape looked very different.

SRStudio/Shutterstock.com

Underneath the Mediterranean Sea lies a 3 km thick layer of salt. This was confirmed in 1970 by the drilling of the Deep Sea Drilling Project, which sampled sediment and rock cores from the seabed of the Mediterranean Sea (and around the world).

This thick layer of salt, along with erosion patterns and fossil evidence, led to the conclusion that the Mediterranean Sea dried up about 6 million years ago. This event is now known as the Messinian salinity crisis.

Although it is not fully understood how this happened, it is suspected that global cooling (leading to increased freezing of glaciers and icebergs and thus lowering sea levels) combined with tectonic shifts caused the Strait of Gibraltar (the narrow passage between to close Europe) peninsula and Africa) caused by the Spaniards and to block the inflow of water from the Atlantic into the sea. Without this constant supply of water from the ocean, the Mediterranean gradually evaporated over the next thousand years. And when that happened, all the salt from the salt water was left behind and locked into the seabed.

Nile erosion creates a gorge

As the water level in the Mediterranean dropped, the gradient of the Nile increased. In other words, the river steepened as it flowed from its headwaters in the highlands of Ethiopia to its mouth in the Mediterranean Sea.

With a steeper gradient and the resulting spectacular waterfalls, the river had more energy and power to erode the land. It has carved a massive canyon through the continental crust, reaching depths of up to 7,900 feet (1.5 miles) below present-day Cairo.

For comparison, the Grand Canyon averages 4000 feet deep and reaches a similar 6000 feet at its deepest point.

Simply put, the Nile flowed in a deeper gorge than the Grand Canyon!

The appearance of this Nile Gorge was more likely to resemble the Gunnison’s Black Canyon in Colorado, which has sheer black walls of a similar type of granite. The walls of the Grand Canyon, on the other hand, are layered with sandstone, shale, and limestone, giving it its distinctive reddish-orange-brown appearance.

The Mediterranean fills up

About 5.3 million years ago, the Mediterranean Sea began to fill up again. Again, the exact mechanism for this is not fully understood, but it was likely a combination of Strait of Gibraltar erosion, tectonic fault activity, and sea level rise.

Some estimates put the floods (called the Zanclean Deluge) raising sea levels in the Mediterranean Sea by as much as 30 feet a day! While it probably took thousands of years for the sea to evaporate, it may have completely refilled in as little as 10 years. However, other geological models suggest it may have taken much longer.

As the sea began to rise, the canyon valley that the river had carved slowly filled with water. At this point the river was not so much a river as more of a bay (a long, deep lake) stretching south to Aswan, 560 miles upstream.

Sediment flow raises the river bed

For the next million years, the water flow of the Nile continued to carry sediments downstream from the highlands. Rising sea levels resulted in a less steep gradient for the river, meaning the river would move more slowly and deposit more sediment.

As the river slowed, it began to meander and form bends, further promoting sediment deposition.

And as more sediment filled the valley of the canyon, the higher the river bed rose. Eventually its waters rose so high that the river was able to overflow its banks again and form the floodplain we see today.

The White Nile flows into the Blue Nile

At some point, probably around 15,000 years ago, the waters of the White Nile joined the Blue Nile and the river took on its present form. At that time, the North African landscape was very different from what it is today. The climate was wetter and the Sahara was not yet a desert but a lush savannah with grasslands, trees and lakes.

The White Nile extends to Lake Victoria in the highlands of Uganda, Tanzania and Kenya. From these headwaters the river meanders north in a continuous flow for over 4000 miles to the Nile Delta where it meets the Mediterranean Sea. This enormous length makes the Nile the longest river on earth (although there is some debate on this point as the Amazon is very short and possibly longer depending on the measurement method used).

On its way to the Mediterranean, the White Nile empties into the other major tributary of the Nile, the Blue Nile. The Blue Nile rises in the Ethiopian highlands and is much shorter than the White Nile. However, despite its shorter length, the Blue Nile actually contributes more water and sediment to the integrated Nile than the White Nile.

The Nile today

Camels in the sandy desert
The limestone slabs for the famous Pyramids of Cairo were driven down the Nile.

givaga/shutterstock.com

Standing on the banks of the Nile today, it’s hard to imagine the magnitude and power of that river in its geological past. On the surface, there is little left of the spectacular gorge that the river once carved. The Nile today is a slow-flowing river meandering through a flat floodplain.

But the Nile is still an incredibly important waterway for the countries it flows through, and has played an important role in the history and culture of the region for many millennia. The river remains an important transportation route, as well as a water source for irrigation, drinking water, and hydroelectric power.

As is well known, the Sphinx and Pyramids of Giza were built near the Nile from blocks of limestone quarried at remote locations and swept down the river on barges. The health and well-being of the Egyptian people has always been closely linked to the health of the river, as its annual floods deposited a rich layer of fertile silt on the land and ensured a good harvest. If the river were not flooded or flooded too much, the harvest would fail and tragic famine would result.

Today, the Nile’s water level is controlled by a series of dams that allow for irrigation and hydroelectric power while protecting against devastating floods.

The ecosystem of the Nile

1664796614 437 Discover why the Nile was once deeper than the Grand - March 19, 2024
Nile Perch can grow to over 6 feet long!

Cheng Wei/Shutterstock.com

The Nile is also home to a wide variety of plants and animals. Papyrus and lotus plants grow in the shallow waters along the banks of the river, and reeds, aquatic grasses and sedges line the banks.

The Nile is home to many species of fish including the Nile Perch which can grow to over 6 feet long and weigh over 400 pounds! Other fish that live in the river are:

The river’s fertile waters and plentiful food sources support many interesting animals, such as:

  • crocodiles
  • hippos
  • cobras
  • rock pythons
  • monitor lizards
  • softshell turtles

The river is also an important stopover for hundreds of migratory bird species. The Nile Delta is a particularly important resting and feeding area for these birds as it is one of the few places in the region with fresh water and plentiful food sources. However, there is concern that these migratory bird species may be partly responsible for the long-distance spread of West Nile virus – a serious disease usually transmitted by infected mosquitoes.

The possible future of the Nile

Aswan, Egypt
The Aswan High Dam was a very helpful resource for Egypt, but it had some unintended consequences.

iStock.com/Givaga

The Aswan High Dam was built in the 1960s to protect Egypt from flooding and generate hydroelectric power. However, the dam had some unintended consequences.

These negative effects include:

  • an increase in soil salinity (salinity)
  • a deterioration in water quality due to contamination from chemical fertilizers and runoff from pesticides
  • the disappearance of some fish species
  • increased spread of human diseases
  • increased vulnerability to climate change and rising sea levels
  • Flooding of important historical sites
  • Displacement of communities that have lived near the Nile for centuries

In addition, economic and political tensions between the countries through which the Nile flows (Egypt, Sudan, South Sudan, Ethiopia, Uganda, Kenya, Tanzania, the Democratic Republic of the Congo, Rwanda and Burundi) have led to disagreements over how to manage the water resources of the best manage the flow.

For example, Ethiopia is currently building the Grand Ethiopian Renaissance Dam on the Blue Nile. The reservoir created by this dam is said to be of great benefit to Ethiopia’s rapidly growing population and economy. Downstream in Egypt, however, they see a significant drop in their water supply as a result.

There are also fears that an excessively hot and dry year (which is becoming increasingly likely due to systemic climate change) could result in devastating droughts that would threaten the lives of the 250 million people who depend on the Nile for drinking water, irrigation, and other needs. Egypt and surrounding areas are already among the most arid places on earth, and a decline in the flow of the Nile could have catastrophic consequences.

With proper management and cooperation between the countries involved, it is possible that the river will support life and prosperity in the region for many years to come. However, the challenges are significant and only time will tell what the future of the Nile will be.

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