The
oldest and best defined rift occurs
in the Afar region of Ethiopia
and this rift is usually referred
to as the Ethiopian Rift. Further
to the South a series of rifts
occur which include a Western
branch, the “Lake Albert
Rift” or “Albertine
Rift” which contains the
East African Great Lakes, and
an Eastern branch that roughly
bisects Kenya north-to-south on
a line slightly west of Nairobi.
[1]
The Great Rift Valley is a name given
in the late 19th century by British
explorer John Walter Gregory to the
continuous geographic trench, approximately
6,000 kilometres (3,700 mi) in length,
that runs from northern Syria in Southwest
Asia to central Mozambique in East
Africa. The name continues in some
usages, although it is today considered
geologically imprecise as it combines
features that are today regarded as
separate, although related, rift and
fault systems. Today, the term is
most often used to refer to the valley
of the East African Rift, the divergent
plate boundary which extends from
the Afar Triple Junction southward
across eastern Africa, and is in the
process of splitting the African Plate
into two new separate plates. Geologists
generally refer to these incipient
plates as the Nubian and Somalian
subplates or protoplates.
The Great Rift Valley
as originally described extends from
Lebanon in the north to Mozambique
in the south, and constitutes one
of two distinct physiographic provinces
of the East African Highlands physiographic
division. The northernmost part of
the Rift, today called the Dead Sea
Transform or Rift, forms the Beqaa
Valley in Lebanon separating the Lebanon
Mountains and Anti-Lebanon Mountains.
Further south it is known as the Hula
Valley separating the Galilee mountains
and the Golan Heights. The River Jordan
begins here and flows southward through
Lake Hula into the Sea of Galilee
in Israel, then continues south through
the Jordan Valley into the Dead Sea
on the Israeli-Jordanian border. From
the Dead Sea southwards, the Rift
is occupied by the Wadi Arabah, then
the Gulf of Aqaba, and then the Red
Sea. Off the southern tip of Sinai
in the Red Sea, the Dead Sea Transform
meets the Red Sea Rift which runs
the length of the Red Sea. The Red
Sea Rift comes ashore to meet the
East African Rift and the Aden Ridge
in the Afar Depression of East Africa.
The junction of these three rifts
is called the Afar Triple Junction.
The Jordan Rift Valley from spaceIn
eastern Africa the valley divides
into two, the Western Rift Valley
and the Eastern Rift Valley.
The Western Rift, also
called the Albertine Rift, is edged
by some of the highest mountains in
Africa, including the Virunga Mountains,
Mitumba Mountains, and Ruwenzori Range.
It contains the Rift Valley lakes,
which include some of the deepest
lakes in the world (up to 1,470 meters
deep at Lake Tanganyika). Lake Victoria,
the second largest area freshwater
lake in the world, is considered part
of the Rift Valley system although
it actually lies between the two branches.
All of the African Great Lakes were
formed as the result of the rift,
and most lie within its rift valley.
In Kenya the valley
is deepest to the north of Nairobi.
As the lakes in the Eastern Rift have
no outlet to the sea and tend to be
shallow they have a high mineral content
as the evaporation of water leaves
the salts behind. For example, Lake
Magadi has high concentrations of
soda (sodium carbonate) and Lake Elmenteita,
Lake Bogoria, and Lake Nakuru are
all strongly alkaline, while the freshwater
springs supplying Lake Naivasha are
essential to support its current biological
variety.[3]
