EAST AFRICAN RIFT VALLEY:

STUDY MAIN MAP RIFT VALLEY

1-How many plates can you find here ? (1,2,3,4?) 2-What is the result of these tectonic plate

movements? 3-What do the dotted lines stand for?

In this area: we see diff erent fault lines (graben or “slenken’ or rifts), it’s a system of ongoing branches. In the long run one of these branches/rifts/ fault lines wil evolve into an ocean (the other fault lines will stop being active). So out of one fault line will develop an ocean because the African Plate will be split and parts will diverge (move away) from each other.

EAST AFRICAN RIFT VALLEY ; 6400 KM L GRABEN (SLENK)

RIFT VALLEY (GRABEN, BASIN (SLENK)

DIVERGING PLATE BORDERS (NEW OCEAN

At the border of the Republ ic of Congo you can see a ser ies of lakes (and next to i t a lso Lake Victor ia) .

See ; Google “Ri ft Val ley”(East Afr ican Ri ft System EARS ) = long system of graben, val leys, bas ins (s lenken) from Syria t i l l Mozambique: total length 6400 km, width 30-100 km and depth 100s t i l l 1000s of metres ( inc luding faul t l ine which runs through the Red Sea and Gul f of Aden

What is the story behind? Theory of Wegener (plate tectonics) developed in the 60’s : the crust ( l i thoshere) is div ided in diff erent plates which dr i ft on the mantle (asthenosphere); empowered by the convection currents o ld theory: cont inents dr i ft over the oceans (Morgan) ;

In the EARS a convection currents heats the crust which becomes br i tt le and cracks/ faul ts appear and certain parts s ink : resul t is g…., the Ri ft Val ley

In this area: we see diff erent faul t l ines (or r i fts or graben (Dutch “s lenken’) . I t ’s a system of ongoing branches. In the long run out of one of these

branches/r i fts / faul t l ines an ocean wi l l evolve ( just l ike the Red Sea). So the Afr ican Plate wi l l be spl i t in two parts which wi l l d iverge (move away) from each other (fi rst we see val leys with lakeslater an ocean)

RIFT VALLEY

G59Three kinds of endogenic eff ects on diff erences in altitude of the earths’s surface

1Horst=2Graben=3Fold= On a fault, pieces of crust can move either h…….. or

v…………. Another name for fault = cr……G60 Plates =Main movements (3)of plates = Mid Atlantic Ridge =At plate boundaries you fi nd v………….. and e…………..

G 59 FOLDS, HORSTS AND GRABENS

G60 PLATES AND FAULTS

Two types of diverging plates:

Mid oceanic ridges or Intercontinental rifts (faults, graben, slenk):

Magma from the mantle (asthenosphere) pours out, solidifies and builds new crust (lithoshpere) which moves away in both directions from the volcanic plume

Africa splits in the Nubian Plate and the Somalian Plate and a new ocean will develop

DIVERGING PLATE BORDERS(MOVE AWAY FROM EACH OTHER)