THE AFRICAN RIFT LAKES, PART 3
THE ANCIENT WATERS OF TANGANYIKA
By Jason Jenkins
From September 2005 Underwater, Iowa Aquarium Society
Aquarticles.com
Millions of years ago, South-Eastern Africa was split in two by tectonic plate shifts
and heavy volcanism. The trenches that formed are now known as the Rift Valley. When these
massive tears in the Earth's crust filled with water, the Rift Lakes were born. The first
lake to become established in the Rift Valley was Lake Tanganyika.
Lake Tanganyika rests between Zaire and Tanzania, with Zaire on the West and Tanzania
to the lake's East. Forming the lake's Northern border is the country of Burundi, with
Zambia making up the Southern border. Formed approximately 20 million years ago, Lake
Tanganyika is among the oldest lakes in the world, and arguably, the oldest. Lake
Tanganyika is also one of the largest bodies of freshwater on the planet. Measuring just
over 420 miles long, and varying between 30 to 50 miles wide in parts, Tanganyika covers
an area of about 12,700 square miles (LoveToKnow), an area a little greater than that of
the country of Belgium (Morfitt). Tanganyika is amazingly deep as well. Plunging to a
depth of 4,700 feet, Lake Tanganyika is the second deepest lake in the world, only outdone
by Russia's Lake Baikal.
The temperature of the surface is only about 5 degrees Fahrenheit warmer than the
waters at the bottom of the lake. Volcanic activity at the lake's floor accounts for this
tiny difference in temperature and causes a high level of dissolved minerals. The lack of
temperature difference means there is a lack of vertical currents. Without the mixing of
the deep water and the water at the surface, oxygen cannot reach a depth greater than 300
feet, leaving the waters of the deep either too high in Hydrogen Sulfide, or too low in
oxygen to sustain life forms (zambiatourism).
Lake Tanganyika first became known to Europeans in February, 1858, during the famous
Burton and Speke expedition. Richard Burton and John Speke arrived on the shores of
Tanganyika at Ujiji, in North Western Tanzania. Burton and Speke were searching for the
source of the Nile River. After exploring the Northern portion of the lake, they soon
discovered that the river they thought was the Nile was actually the Ruizizi River. To
their astonishment, the Ruizizi flowed into, not out of the lake. A few years later,
Stanley, another explorer of the region would encounter the missing Dr. Livingstone and
utter the famous sentence "Dr. Livingstone, I presume" (Eco-resorts) on the
Ujiji shore of the lake.
More recently, Lake Tanganyika has become famous for its amazing bio-diversity. The
incredibly stable environment, age, and isolation of Lake Tanganyika has allowed the fauna
of the lake to evolve into very unique, specialized creatures. The bio-mass of Tanganyika
has evolved so very similarly to that of the oceans that it is believed that Lake
Tanganyika was connected to the Indian Ocean during the Jurassic period. This theory has
had a shadow of doubt cast upon in recent times, though, most notably the fact that there
is an "almost entire absence of marine fossiliferous beds in the whole of equatorial
Africa at a distance from the sea, of any remains of Jurassic faunas which might link the
Tanganyika forms with those of undoubted Jurassic age in neighboring regions. The
formation of the existing rift-valley seems in any case to date from Tertiary times
only." (LoveToKnow)
After seeing the organisms that inhabit Lake Tanganyika, it is understandable how the
theory of Tanganyika being connected to the Indian Ocean was made. The immense size of
Tanganyika, and its nearly uniform temperature, has made the lake extremely stable, much
like the oceans. The lake hosts a variety of species normally thought of as ocean
dwelling. Among some of the life forms encountered in Lake Tanganyika are fresh water
puffers, several varieties of snails that are remarkably similar to their ocean-faring
counterparts, as well as crabs and mollusks. Even some of the cichlids have evolved
similarly to oceanic fish. Cyprichromis Lepstoma is occasionally called the "sardine
cichlid", while the Eretmodus family has evolved very closely to that of the Gobies
of the ocean.
Lake Tanganyika has been receiving an increasing amount of attention due to the rapid
speciation of its cichlids and the variety of endemic life it supports. Due to its size
and relative inaccessibility, much of Lake Tanganyika has yet to be explored. Further
study of the lake could give us some answers as to how evolutionary forces play out. It is
only a matter of time before more species are discovered and more information is gathered
on the life the lake has birthed. The variety of unique species, and the specialized
niches they have evolved to fill, can only cause us to wonder at what else has yet to be
discovered.
1."Tanganyika." LoveToKnow 1911 online Encyclopedia. 2003, 2004 LoveToKnow. http://58.1911encyclopedia.org/T/TA/TANGANYIKA.htm
2.Rees, Melinda. Lake Tanganyika. Eco-Resorts.com 2003-2005 http://www.eco-resorts.com/LakeTanganyika.php
3.Mortiff, Craig. "Lake Tanganyika and its Diverse
Cichlids". Fish Tales, Bermuda Fry-Angle Aquarium Society; Buntbarsche Bulletin.
2003-2005
4.www.zambiatourism.com. "Lake Tanganyika
& Mpulungu" 5.www.ilec.or.jp "Lake Tanganyika"
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