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Red Sea Region Parting in Massive Split

Stefan Lovgren
for National Geographic News
July 19, 2006
 
Moses may have received some geological assistance when he parted the Red Sea to let the Israelites through, according to the Bible.

In a new study, scientists have determined that a recent tear in Earth's continental crust near the sea is the largest single rip seen since satellite monitoring began. (Related story: Noah's Ark Discovered in Iran? [July 5, 2006].)

For the past 30 million years the Arabian tectonic plate has been moving away from the African (Nubian) plate at the Red Sea.

But the rift, in which Earth's crust is being stretched and thinned, is not happening smoothly.

Most of the time the plates are stuck together. But in September of last year they split apart along a 37-mile (60-kilometer) section in Afar, Ethiopia (Ethiopia map), near the southern end of the Red Sea.

The scientist's observations may help to explain how Earth's plates split apart and how new crust forms.

The study suggests that the splitting is due to the injection of underground magma (molten rock) into the rift rather than earthquakes happening on tectonic faults.

"It is clear that the rise of molten rock through the plate is enabling the breakup of Africa and Arabia," said Tim Wright, an earth and environmental scientist at the University of Leeds in the United Kingdom.

Wright is the lead author of the study, which is reported in tomorrow's issue of the journal Nature.

Continental Divide

The scientists used data from the European Space Agency's Envisat radar satellite to analyze how the ground moved during the rifting episode.

A similar event occurred in Iceland from 1975 to 1984, but it took nine years and 20 individual "rips" to achieve what happened in Ethiopia in just a few weeks.

The two plates in Ethiopia moved apart by 26 feet (8 meters). As they did so, 0.6 cubic mile (2.5 cubic kilometers) of magma—enough to fill more than 2,000 football stadiums—was injected into a vertical crack known as a dyke.

Above the dyke, faults moved by several meters and fissures opened up in Earth's surface.

More than 160 earthquakes were detected in the area during this time. Some 10,000 local people were displaced, and several camels and goats fell into the open fissures.

Magma Intrusion

But it is the process of magma intrusion into the gap, rather than the cracking of the crust, that is responsible for controlling plate spreading in these settings.

"The process is very similar to the way the crust grows at mid-ocean ridges, such as the one running along the center of the Atlantic Ocean," Wright said.

Gezahegn Yirgu, a co-author of the study, says the September rift is a reminder of the awesome geological changes taking place on Earth.

"The event was a vivid expression of the unimaginable amount of stored energy the Earth releases from time to time to split apart continents," said Yirgu, who is an earth scientist at the University of Addis Ababa in Ethiopia.

The tectonic plates are moving apart at about the same speed that fingernails grow (a few centimeters per year).

"We don't know if an ocean will eventually be formed here, but the prospects are good," Wright said. "It just may take a million years before the port can be built."

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