1) The document discusses the tectonic and volcanic history of the Northern Main Ethiopian Rift System. It began forming around 30 million years ago through regional extension and the formation of half-graben basins. 2) Around 8 million years ago, basaltic magmas erupted and formed shield volcanoes and cinder cones in the rift valley. The modern rift morphology developed around 3 million years ago as the valley widened and deepened. 3) The Northern Main Ethiopian Rift System continues evolving through ongoing extension and volcanic activity, making it one of the most seismically and volcanically active regions in Africa.

1. ADAMA SCIENCE AND TECHNOLOGY
UNIVERSITY
SCHOOL OF APPLIED NATURAL SCIENCE
DEPARTMENT OF APPLIED GEOLOGY
POSTGRADUATE PROGRAM
ADVANCED STRUCTURAL GEOLOGY AND TECTONICS
Prepared by Fikadu Teferi
PGR/28045/15
Presented to: Dr.Melese (PhD)
March 10,2023

2. Discuss tectonic/structural and volcanic history of Northern Main
Ethiopian Rift System and their kinematic and geodynamic evolution?
Subject

3. INTRODUCTION
The Great Rift Valley is located between the Somali Plateau and the
Ethiopian Plateau.
The MERS is formed by the divergent movement of three tectonic plates:
the Nubian, Arabian, and Somalian plates.
During the Miocene Era, along the East African Rift System, the Nubian and
Somali plates started to separate, leading to the formation of the rift.
Deformation began around 18 million years ago at the south end, around 11
million years ago close to the Afar depression and probably around 6-8
million years ago in the central sector.(E. Beutel, J. Wijk ,2010)

4. CONT.
The Ethiopian rift valley is about 80 kilometres (50 mi) wide and bordered
on both margins by large, discontinuous normal faults that give rise to major
tectonic escarpments separating the rift floor from the surrounding plateaus
The valley floor is occupied by a series of interconnected lakes, including
Lake Abaya, Lake Chamo, Lake Langano, and Lake Hawassa.

5. CONT.
The MERS is also characterized by
numerous volcanic features,
including shield volcanoes,
stratovolcanoes, and calderas. Some
of the most prominent volcanic
centers in the MERS include Mounts
Zuqualla, Fentale, and Fantale.(Keir
et al., 2013).

6. NORTHERN MAIN ETHIOPIAN RIFT
Discontinuous and diachronous evolution of the Main Ethiopian Rift.(K. Keranen, S. Klemperer)

7. CONT.
is characterized by a series of basins and volcanic
plateaus, including the Afar Depression, which is
one of the most active volcanic areas in the world.
The Northern MER is considered to extend from
the Afar Depression up to the Lake Koka region
following the Middle course of the Awash River
Valley. The boundary between the Afar
Depression and the Northern MER is not readily
recognizable within the rift floor.

8. TECTONIC EVOLUTION OF NMERS
The northern Main Ethiopian Rift (MER) is a segment of this system that
stretches from the Ethiopian highlands to the Red Sea.
The tectonic evolution of the northern MER can be divided into three main
phases
1. Pre-rift phase (Late Precambrian to Early Paleozoic)
2. Rift initiation phase (Late Oligocene to Early Miocene)
3. Active rifting phase (Middle Miocene to present)

9. CONT.
1. Pre-rift phase (Late Precambrian to Early Paleozoic)
During this phase, characterized by the formation and subsequent
deformation of the Arabian-Nubian Shield (ANS)
 The ANS is a large, complex terrane made up of various lithologies,
including gneisses, granites, and volcanic rocks. The ANS was subsequently
affected by several phases of deformation, metamorphism, and magmatism.

10. CONT.
The ANS formed as a result of the collision of the East African Orogen with
the West African Craton during the Pan-African orogeny. The orogeny was a
major tectonic event that occurred approximately 600 to 500 million years
ago, and it resulted in the amalgamation of several terranes, including the
ANS.

11. CONT.
2. Rift initiation phase (Late Oligocene to Early Miocene)
The northern MER began to form during this phase, as a result of
extensional tectonics associated with the opening of the Red Sea and Gulf of
Aden.
The first phase of rifting was characterized by the formation of normal
faults, which produced a series of half-grabens that were subsequently filled
with sediments.

12. CONT.
• marked by the onset of extensional tectonics that led to the formation of the
rift.
• The initiation of the rift was associated with the opening of the Red Sea and
Gulf of Aden, which caused extensional stresses to be transmitted inland
along the East African Rift System.
• During this phase, the northern Ethiopian Rift System was characterized by
the formation of normal faults that caused the crust to be extended and
thinned.(J. Petruska , 2019)

13. CONT.
Geologic evolution of Ethiopian rift
system
(http://ethiopianrift.igg.cnr.it/rift%20
valley%20significance.htm)

14. CONT.
3. Active rifting phase (Middle Miocene to present)
During the active rifting phase of the MERS, a series of parallel faults have
created a series of grabens, or down-dropped blocks, which are separated by
uplifted blocks.
The most active segment of the MERS is the Afar Depression, which is
located at the triple junction of the African, Arabian, and Somali plates.

15. CONT.
Rift segment towards the
Dabbahu volcano (Photo by
Elizabeth , University of
London.)

16. KINEMATIC AND GEODYNAMIC EVOLUTION
The Northern Main Ethiopian Rift System (NMERS) is an active tectonic rift
system that has evolved through a complex interplay of tectonic, magmatic, and
erosional processes.
 The kinematic and geodynamic evolution of the NMERS can be divided into
several stages, each characterized by distinct tectonic and magmatic processes.
 The first stage of NMERS evolution
began around 30 million years ago, with the onset of regional extension and the
formation of a series of half-graben basins.
These basins were filled with sedimentary and volcanic rocks, including rhyolites,
trachytes, and basalts.

17. CONT.
 Second stage of NMERS evolution
began around 8 million years ago, basaltic magmas began to erupt and flood
the rift valley, forming a series of large shield volcanoes and cinder cones.
This phase of volcanism was accompanied by the formation of numerous
normal faults and grabens,
The third stage of NMERS evolution
 began around 3 million years ago, with the onset of the modern rift valley
morphology.
began around 3 million years ago, with the onset of the
modern rift valley morphology.

18. CONT.
During this stage, the rift valley widened and deepened, and the topography
became more rugged and dissected.
This stage was characterized by the continued activity of normal faults and
grabens, as well as the emplacement of large volumes of basaltic lava flows.
The fourth stage of NMERS evolution is ongoing,
characterized by continued extension and volcanic activity.

19. CONT.
The rift valley is still widening and deepening, and the area is prone to
frequent seismic activity and volcanic eruptions.

20. CONCLUSION
 NMERS has a complex tectonic and volcanic history that spans several
stages of evolution.
The rift system began to form around 30 million years ago, with the onset of
regional extension and the formation of half-graben basins followed by a
phase of explosive volcanic activity that lasted until about 8 million years
ago, when basaltic magmas began to flood the rift valley, forming shield
volcanoes and cinder cone

21. CONT.
 The rift valley continued to evolve throughout the subsequent stages of
NMERS evolution, with ongoing extension and volcanic activity.
The area is prone to frequent seismic activity and volcanic eruptions, and is
considered to be one of the most active volcanic regions in Africa.
The geodynamic evolution of the NMERS is driven by the interaction of the
African, Arabian, and Somali plates, as well as the presence of a mantle
plume beneath the region.

22. Thank You