National Geographic : 2010 Jul
WILLIAM E. MCNULTY, NGM STAFF ART: GARY HINCKS SOURCES: GIDAY WOLDEGABRIEL, LOS ALAMOS NATIONAL LABORATORY AND TIM D. WHITE, UNIVERSITY OF CALIFORNIA, BERKELEY SATELLITE IMAGE: NASA/JPL TIME TRAVEL The Great Rift Valley of eastern Africa is uniquely suited to create and preserve fossils. Beneath the surface, continental plates are pulling apart (map, right). Millions of years of tectonic activity and sedimentation have buried, preserved, and brought back to the surface the remains of hominids that once inhabited the region. Associated volcanic material can often be dated. ARDI'S JOURNEY After Ardi died, her bones were quickly buried. Minerals began to replace organic materials. As rifting continued, the Afar Basin sank and filled with sediments. Faulting, uplifting, and erosion conspired to reexpose her fossilized bones. 1.0 2.5 HATA HERTO DAKA Sediment age (in millions of years) 0.16 4.18 4.4 4.3 5.2 ARAMIS Yardi Lake 2 MILES 2.5 MILES N N Au. anamensis Homo sapiens H. erectus Au. garhi Ar. ramidus Herto village ROUTE END START ROUTE END START BOURI WALK ARAMIS WALK 200 MILES Rift margin AFAR BASIN Today 4.4 m.y.a. Millions of years of sediments lie exposed on the surface. Rifting uplifts sediments, exposing Ardi. Ardi is buried and fossilized underground. SOMALIAN PLATE SOMALIAN PLATE NUBIAN PLATE NUBIAN PLATE ETHIOPIA SUDAN UGANDA ERITREA DJIBOUTI SOMALIA KENYA SOMALIAN PLATE NUBIAN PLATE Rift margin Addis Ababa AFAR BASIN 0mi 200 0km 200 EAST AFRICAN RIFT ZONE AREA OF DETAIL AFRICA AUTHOR'S ROUTE Jamie Shreeve spent two days walking and covered about five million years.