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Questions and Answers
What processes occurred with the retreat of the sea in the Horn of Africa and Ethiopia?
What processes occurred with the retreat of the sea in the Horn of Africa and Ethiopia?
- Deposition of clay, silt, sand conglomerate, gypsum, shale, and sand (correct)
- Erosion of the land and deposition of limestone and sandstone
- Formation of new landmass and deposition of sedimentary rocks
- Deposition of clay, silt, sand conglomerate, and limestone
Which sedimentary formations were laid and formed upon the Precambrian rock surface at the end of the Mesozoic Era?
Which sedimentary formations were laid and formed upon the Precambrian rock surface at the end of the Mesozoic Era?
- Adigrat sandstone, Hintalo limestone, and Upper Sandstone (correct)
- Clay, silt, and conglomerate
- Gypsum, shale, and sandstone
- Erosion, deposition, and uplift
What covers 25% of the land mass of the country?
What covers 25% of the land mass of the country?
- Adigrat sandstone
- Mesozoic sedimentary rocks (correct)
- Hintalo limestone
- Upper sandstone
What factor caused the age and thickness of the Sandstone layers to vary in a Southeast - Northwest direction?
What factor caused the age and thickness of the Sandstone layers to vary in a Southeast - Northwest direction?
Which formation is older and thicker in the southeast but progressively decreases in age and thickness northwestward?
Which formation is older and thicker in the southeast but progressively decreases in age and thickness northwestward?
What was laid over the Hintalo limestone as transitional formations?
What was laid over the Hintalo limestone as transitional formations?
What geological event had an important effect on the present-day landmass of Ethiopia and the Horn of Africa?
What geological event had an important effect on the present-day landmass of Ethiopia and the Horn of Africa?
During which geologic period did the uplifting of the whole Arabo-Ethiopian landmass begin?
During which geologic period did the uplifting of the whole Arabo-Ethiopian landmass begin?
What type of rocks extensively cover most parts of Ethiopia as surface rocks?
What type of rocks extensively cover most parts of Ethiopia as surface rocks?
Where did the transgressing sea and Mesozoic sediments nearly cover the whole of Ethiopia?
Where did the transgressing sea and Mesozoic sediments nearly cover the whole of Ethiopia?
What event resulted in the outpouring of a huge quantity of lava and the formation of the Ethiopian plateau surface?
What event resulted in the outpouring of a huge quantity of lava and the formation of the Ethiopian plateau surface?
In which era are the Mesozoic rocks overlaid by the Cenozoic rocks in most parts of Ethiopia?
In which era are the Mesozoic rocks overlaid by the Cenozoic rocks in most parts of Ethiopia?
What is the most recent geologic Era?
What is the most recent geologic Era?
Where are old marine sediments extensively found as surface rocks?
Where are old marine sediments extensively found as surface rocks?
What was pushed up to a maximum height of 2,000 meters above sea level during the Eocene epoch?
What was pushed up to a maximum height of 2,000 meters above sea level during the Eocene epoch?
What occurred along with the uplifting of the Arabo-Ethiopian landmass during the Eocene epoch?
What occurred along with the uplifting of the Arabo-Ethiopian landmass during the Eocene epoch?
What is the name of the volcanic material known as in the text?
What is the name of the volcanic material known as in the text?
What geological theory is related to the formation of the Rift Valley according to the text?
What geological theory is related to the formation of the Rift Valley according to the text?
During which era did the major rifting affecting the whole African Rift System, including Ethiopia, take place?
During which era did the major rifting affecting the whole African Rift System, including Ethiopia, take place?
What caused parallel fractures or faults on the sides of the up-arched swell according to the text?
What caused parallel fractures or faults on the sides of the up-arched swell according to the text?
What is the name given to the extensive structural depression formed by the collapse of the central part of the landmass?
What is the name given to the extensive structural depression formed by the collapse of the central part of the landmass?
What geological event likely began in the late Oligocene and Miocene Epochs of the Cenozoic Era?
What geological event likely began in the late Oligocene and Miocene Epochs of the Cenozoic Era?
What geological effect did the formation of the Rift Valley have?
What geological effect did the formation of the Rift Valley have?
What was the outcome of reversed tilting and volcanic activity during the Pleistocene period?
What was the outcome of reversed tilting and volcanic activity during the Pleistocene period?
What resulted from similar tectonic activities in the Lake Tana Basin?
What resulted from similar tectonic activities in the Lake Tana Basin?
Which area experienced uplifting to form the Afar Block Mountains during the Pleistocene period?
Which area experienced uplifting to form the Afar Block Mountains during the Pleistocene period?
What was a consequence of reversed tilting and volcanic activity during the Pleistocene period?
What was a consequence of reversed tilting and volcanic activity during the Pleistocene period?
What was an outcome of rifting and faulting in Ethiopia during the Pliocene and Pleistocene Epochs?
What was an outcome of rifting and faulting in Ethiopia during the Pliocene and Pleistocene Epochs?
What happened during the Pliocene period as a result of rifting and faulting in Ethiopia?
What happened during the Pliocene period as a result of rifting and faulting in Ethiopia?
What was an effect of similar tectonic activities in Lake Tana Basin other than graben formation?
What was an effect of similar tectonic activities in Lake Tana Basin other than graben formation?
What was one outcome of rifting and faulting in Ethiopia during Pliocene and Pleistocene Epochs?
What was one outcome of rifting and faulting in Ethiopia during Pliocene and Pleistocene Epochs?
What occurred due to reversed tilting and volcanic activity?
What occurred due to reversed tilting and volcanic activity?
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Study Notes
Geological History of the Horn of Africa and Ethiopia
- The retreat of the sea in the Horn of Africa and Ethiopia led to the exposure of Precambrian rocks.
- At the end of the Mesozoic Era, sedimentary formations laid upon the Precambrian surface included sandstones, mudstones, and limestones.
- Sedimentary layers laid down varied in age and thickness due to northwestern tectonic stresses.
- In the southeast, the Hintalo limestone formation is older and thicker, decreasing in age and thickness toward the northwest.
Geological Cover and Composition
- Cenozoic rocks overlay the older Mesozoic rocks across most of Ethiopia, reflecting a major geological transition.
- Approximately 25% of Ethiopia's land mass is covered by volcanic rocks originating from extensive volcanic activity.
- Eocene uplifts pushed geological formations to heights reaching up to 2,000 meters above sea level.
Formation of the Ethiopian Landmass
- The transgressing sea and Mesozoic sediments covered much of Ethiopia during the Mesozoic era.
- The extensive plateau surface of Ethiopia formed due to massive lava outpourings during the volcanic geological events.
- The Rift Valley formation relates to tectonic plate movements resulting from faulting and rifting dynamics.
Significant Geological Events
- Major rifting affecting the African Rift System occurred during the Late Oligocene and into the Miocene Epochs of the Cenozoic Era.
- Uplifting of the Arabo-Ethiopian landmass coincided with volcanic activity during the Eocene epoch.
- An extensive structural depression, known as a graben, formed due to the collapse of the landmass’ central portions.
Effects of Tectonic Activity
- Pleistocene volcanic activity in the region resulted in reversed tilting and significant geological changes.
- Uplifting to create the Afar Block Mountains occurred during the Pleistocene, representing notable elevations as a result of tectonic movements.
- Similar tectonic activities in the Lake Tana Basin yielded significant geological formations, including grabens and volcanic features.
Consequences of Tectonic Dynamics
- Rift-related faulting and volcanic activity during the Pliocene and Pleistocene epochs had profound impacts on the landscape.
- Overall, reversed tilting and volkcanism led to dramatic alterations in topography and environmental conditions in the region.
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