Omo River

Over a very long time, layers of sediment and volcanic ash built up in the Omo Valley.

Scientists use these layers like a clock.

UNESCO says the lower Omo Valley has age-old layers of sediment from the Pliocene and Pleistocene. Scientists have measured their ages, building time scales that run from about 1 million to 3.5 million years ago.

Some layers are volcanic ash. A 2022 study in the journal Nature matched one ash layer in the valley to a big eruption of Shala volcano, in the Main Ethiopian Rift, and dated it.

UNESCO: the Lower Omo Valley's sedimentary deposits go back to the Plio-Pleistocene, and research there has established bio-stratigraphical, radiometric and magneto-stratigraphical scales spanning between one and 3.5 million years, making Omo a yardstick for other ancient deposits in East Africa.

Vidal et al. (Nature, 2022) linked the KHS Tuff, a fine ash layer more than 2 m thick in the Omo-Kibish Formation, to a major explosive eruption of Shala volcano in the Main Ethiopian Rift, dated to 233 ± 22 thousand years ago.

Scientists have found many fossil bones in the Omo Valley.

They help us learn how people came to be.

UNESCO says many hominid fossils have been found in the lower Omo Valley, including pieces of Australopithecus. Ancient stone tools found at a camp there are evidence of some of the oldest known tool-making.

In the late 1960s, scientists found fossil remains now called Omo I. The 2022 Nature study says they are one of the two Ethiopian finds most widely accepted as Homo sapiens, our own species. It dated an ash layer above them to about 233,000 years ago, so Omo I is at least that old.

The deposits have produced numerous hominid and animal fossils, including fragments of Australopithecus, and stone tools from an encampment that offer evidence of the oldest known technical activities of prehistoric beings (UNESCO).

Omo I was discovered in the late 1960s near the top of Member I of the Omo-Kibish Formation. Vidal et al. (2022) call it, with the Herto finds, one of the most widely accepted fossils showing unequivocal modern cranial features (a tall cranial vault and a chin), and give a new minimum age of 233 ± 22 thousand years, older than the age of around 197,000 years usually reported.

The Omo flows into Lake Turkana. The lake has no river flowing out.

Crocodiles and hippos live there, and many birds stop to rest.

Lake Turkana has no outlet: its water leaves mainly by evaporating in the hot, dry air, says the World Lake Database. UNESCO calls it the most saline lake in East Africa and the largest desert lake in the world.

Nile crocodiles and hippos breed on islands in the lake, and UNESCO counts more than 350 kinds of water and land birds there. The lake is also an important stopover for migrating birds.

Lake Turkana has no outlet; water is lost mainly by evaporation, estimated at 2,335 mm a year, so its level depends on the balance between inflow and evaporation (ILEC). UNESCO describes it as the most saline lake in East Africa and the largest desert lake in the world.

The island national parks are breeding habitats of the Nile crocodile, the hippopotamus and several snake species; more than 350 aquatic and terrestrial bird species are recorded, and the lake is an important stopover for Palearctic migrant birds (UNESCO).

Never go near the river without a grown-up.

Cover your arms and legs so mosquitoes can't bite.

Drowning can happen in seconds and is often silent. The CDC says children should always be watched closely near water, even if they have had swimming lessons.

Mosquitoes can spread germs that make people sick. The CDC says to use insect repellent and wear loose, long-sleeved shirts and long pants.

CDC drowning guidance: drowning happens in seconds and is often silent; children who have had swimming lessons still need close and constant supervision in or around water.

CDC mosquito guidance: use EPA-registered insect repellents and wear loose-fitting, long-sleeved shirts and pants, since mosquitoes bite day and night and spread germs that cause illness.