The tremors began on July 12, so faint that they were barely noticed. A week later, a couple of good jolts sent people fleeing their offices in downtown Nairobi. Then the tremors were gone.

Scientists are still unsure about what exactly caused this "earthquake swarm"—a cluster of relatively mild shakes spaced out over several days in Kenya and Tanzania. The quakes—one of which reached magnitude 5.9—caused little damage but spread fear that a big quake was imminent. (What is an earthquake?)

Was it fault activity along the Rift Valley, where the African tectonic plate is stretching? Or was it Ol Doinyo Lengai, a Tanzanian volcano that sits near the swarm's epicenter?

"Mountain of God" Takes the Heat

So far, government officials have pushed the theory that rumbling in Ol Doinyo Lengai—whose name means "Mountain of God" in Masai, was to blame for the tremors.

Fears that a massive eruption was near triggered several hundred people to evacuate its slopes, and the Tanzanian government warned tourists to stay away.

Read more of this article here .

Original Source: Nicholas Wadhams, National Geographic News

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