Pleistocene Pluvial Lakes in East Africa

Morgan Monz

Outline

• Locations • Modern climates• Evidence for pluvial Lakes • Pleistocene glaciation • Specific pluvial lakes

Location

• Victoria

• Tanganyika

• Malawi

(http://www.biomedcentral.com/content/figures/1471-2148-5-17-1-l.jpg)

Modern Day Climates

• Arid to semi arid

• Climate trend

• Ratio of precipitation to potential evaporation (PET)

(http://www.grida.no/images/series/vg-africa/graphics/25-aridity.jpg)

Hydrologic cycle

• Hadley Cells• Intertropical Convergence Zone (ITCZ) • Bimodal distribution

(http://upload.wikimedia.org/wikipedia/commons/d/d7/ITCZ_january-july.png)

Evidence for Pluvial Lakes

• Geomorphologic

• Geochemical

• Archeological (http://farm3.staticflickr.com/2557/5774714465_db908f9385_z.jpg)

Glaciation in Pleistocene

• Three major periods

• 30% of Earth’s surface was glaciated periodically

• Cooler climates lead to less evaporation and less precipitation

Glaciation in Pleistocene

• Abrupt Termination of LGM

• Milankovitch cycles

• Increased insolationhttp://user.gs.rmit.edu.au/caa/global/graphics/insolation.jpg

Lake Victoria

• Shallow basin between branches of rift valley

• Levels of total organic carbon andhydrogen content

• Paleosol records

• Seismic profiles(http://www.eoearth.org/files/119601_119700/119602/400px-Lake_victoria_basin.jpg)

Lake Tanganyika• Occupies several rift

basins within the Western Rift Valley

• Two intervals of dramatic drop during late pleistocene

• Pollen records(http://www.ncdc.noaa.gov/paleo/pubs/tierney2008/tanganyika.jpg)

Lake Malawi

• Rift Basin along the East African Rift

• Diatom assemblages

• About a 100 m drop in lake levels with the Last Glacial Maximum

(http://www.eosnap.com/public/media/2011/11/malawi/20111108-malawi-thumb.jpg)

Summary

• East Africa has experienced a variety of climatic conditions

• Large scale glaciation can be correlated to pluvial periods

• Evidence for multiple dramatic lake level fluctuations in East Africa

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