Are plate tectonics about to tear Africa in two, along the Great Rift Valley on which Israel also sits? Could Israel be in store for devastating earthquakes as the Nubian and Somali continental plates lurch apart, and the strained crust bursts open?
The 50-foot deep crack in the earth that began to develop near Nairobi in Kenya on March 18 could be a sign of impending continental split, some experts warned. Others think the gully, which gapes as much as 60 feet wide, was caused by rains washing away loose soil, nothing more, and suggest fixing the road and moving on.
Indeed plate tectonics are tearing Africa in two, says Dr. Ron Avni of the Ben-Gurion University of the Negev: "We don't need the crack in Kenya to know that," he told Haaretz.
But that evidently isn't why the earth suddenly yawned in Kenya, though the area is indeed squatting on a vast fault. In any case, it will take millions of years for Africa to split into two, creating a new mega-island of the Somali plate: 20 million years, 50 million – what difference does that make, Avni points out.
So meanwhile, is this crack a harbinger of impending mega-quake in Africa and the Middle East? Not likely.
It is true that most of Africa sits on the Nubian Plate, a.k.a. the African plate, which geologists estimate is roaring northward at a brisk clip of 2.15 centimeters a year. But the rest of Africa sits on the Somali Plate. Relative to each other, these two plates are moving apart. (The African plate is moving north relative to the microplate on which Israel sits, Avni says.)
The chasm that split agricultural fields and the Narok highway in southwest Kenya near Nairobi could theoretically have been caused by rifting as the African Plate in the west separates from the Somali Plate to the east. To be sure, the Kenya crack definitely is in the Rift Valley, which starts in Mozambique, passes through most of eastern Africa all the way to Israel – the Red Sea, Dead Sea and Sea of Galilee all sit in it.
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Hotbed of seismic motion
The Great Rift Valley is quite the hotbed for seismic activity over eons. It was the source of the earthquakes that leveled cities in ancient and historic Israel, including the temblor that flattened towns from Hippos to Jericho (and beyond) in 749 C.E. Tremors under and around the Dead Sea are constantly reported, but most are low-key, and are only rarely felt without sensors.
No major seismic activity has been reported in this area of Kenya lately, though some media outlets point out that sensory equipment there is sparse. Still, if there had been a major quake, the world – and locals - would have noticed.
He hasn't had a chance to study the site personally but Dr. Avni notes that based on media reports, the gully annoying local farmers is apparently in soil, not rock, and results from heavy rain causing the local collapse of loose ground.
It's not quite the same as the sinkholes around Israel's Dead Sea, which are caused by groundwater depletion, the salt sea shrinking and freshwater melting the salt that's "holding" the ground together. In this case, the soil, originating in volcanic ash, was loosened by heavy rain combined with underground streams.
"To be of tectonic origin, there would have to be a crack in the bedrock. That would be dramatic," Avni says, and drives it home: however impressive the crack in Kenya, it's no geological drama. "The soil there is apparently really poor, like the loess in Israel's south," he adds.
Only "deep" research, so to speak, beneath the fissure, connecting it to a new crack or new displacement appeared in the bedrock, would be proof, Avni sums up.
Also, though impressive by human dimensions, the crack is not continuous, as one would expect a mini-canyon caused by shifting tectonic plates to be, the Guardian points out. Nor, it reports, have satellite images noticed large-scale deformation of the land, as one would expect if deep-lying magma driving plate tectonics had been on the move.
The volcanic ash that created the soil arose from prehistoric eruptions along the Great Rift Valley.
Meanwhile the Kenyan authorities have fixed the highway (reportedly twice and counting) while hoping it doesn't collapse again. And Israelis definitely have cause to fear earthquake, but less because of the Great Gully that seems to have opened up in this Kenyan field and more because, as we said, we're sitting smack in the north end of the Great Rift Valley.