A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic...
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Transcript of A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic...
![Page 1: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/1.jpg)
•A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea▫Oceanic crust began
forming in the Gulf of Aden about 10 million years ago
▫Red Sea rifting began later and oceanic crust is now forming
East African Rift
![Page 2: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/2.jpg)
•Rifting in East Africa is in its early stages, ▫The continental crust has not yet stretched
and thinned enough for new oceanic crust to form from below
•Nevertheless, this area shows seismic activity and considerable volcanism
•In the Red Sea, rifting and the Late Pliocene origin of oceanic crust followed vast eruptions of basalt
East Africa Rifting
![Page 3: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/3.jpg)
•In East Africa, the continental crust has not yet stretched and thinned enough for oceanic crust to form from below
•In the Middle East the movement of Arabian plate northward against Eurasia causes much tectonic activity
East African Rift
![Page 4: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/4.jpg)
•Circum-Pacific orogenic belt and the Alpine-Himalayan orogenic belt are the sites of most recent geologic and orogenic activity
Orogenic Belts
![Page 5: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/5.jpg)
•Folded rocks in the Alps of SwitzerlandAlps
![Page 6: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/6.jpg)
•The Indian plate moved northward for millions of years until it collided with the Eurasian plate
India Collides with Eurasia
![Page 7: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/7.jpg)
High pCO2 during early Eocene
•Large-scale volcanism
•Giant’s Causeway in N. Ireland
•Early Tertiary age
![Page 8: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/8.jpg)
What prompted Cenozoic climate decline and the onset of glaciation?
Main factors:1. Continental drift
Isolation of Antarctica and initiation of sub-Antarctic oceanic circulation; ice-sheet formationIsolation of Arctic Ocean; sea-ice formation
2. OrogenesisIsolation of continental interiors, particularly of Central Asia, as a result of uplift of the Himalayas and Tibetan Plateau. High altitude areas = more snow cover = high albedo = regional cooling.
![Page 9: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/9.jpg)
Decreasing pCO2 after ~50 Ma
•Collision began ~50 Ma
•Increased weathering = Atm. CO2 decrease
•CaSiO3 + CO2 = CaCO3 + SiO2
![Page 10: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/10.jpg)
Neogene Life
•Isolation of Antarctica led to glaciation▫Global cooling
![Page 11: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/11.jpg)
The Ice Age
• Isthmus of Panama ▫Emplaced 3.5–3 M
years ago▫Started modern
circulation Gulf stream
carries salty Atlantic north
Cools, sinks Oceanic
conveyor belt
![Page 12: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/12.jpg)
Cenozoic Life
•Marine organisms survived mass extinction at the end of the Cretaceous▫Populated oceans during Cenozoic Era
•Forest (angiosperm) began to dominate land
•Grasses appeared as climate cooled▫Diversification of many new mammals
resulted
![Page 13: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/13.jpg)
Oligocene Epoch
•Climate continued to get drier and cooler▫Favored growth of grasses and cone-
bearing and hardwood trees•Earlier types of mammals became extinct•Larger species flourished
▫Deer, pigs, horses, camels, cats, & dogs▫Link
![Page 14: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/14.jpg)
Ice Age—Pleistocene •Climate began to cool and new animals
evolved▫Mammoth▫Saber-toothed cat▫Modern Humans – Homo Sapiens
![Page 15: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/15.jpg)
Baby Mammoth
http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/5262616/Secrets-of-37000-year-old-baby-mammoth-revealed.html
http://img.rian.ru/images/10412/88/104128804.jpg
![Page 16: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/16.jpg)
Humans•First bipedal humanlike primates
appeared about 6 million years ago during the Late Miocene
•Earliest modern humans appeared about 195,000 years ago
•Migration was influenced by Ice Age▫Bering Strait was exposed and
Humans likely walked across to North America
![Page 17: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/17.jpg)
Pleistocene Epoch•Several periods of glaciations
▫Animals had special characteristics that allowed them to endure the cold
▫Other animals moved to warmer regions▫Less-adaptable species became extinct
•Fossils of early ancestors of humans appear▫Hunters which led to extinction of many
large mammals
![Page 18: A triple junction joins the East African Rift System to the Gulf of Aden and the Red Sea ▫Oceanic crust began forming in the Gulf of Aden about 10 million.](https://reader036.fdocuments.us/reader036/viewer/2022081501/56649ef05503460f94bffe38/html5/thumbnails/18.jpg)
Holocene Epoch
•Includes present▫Began when last ice age ended▫As ice sheets melted, seas rose and
coastlines took shape•Great Lakes filled•Modern humans developed agriculture
and began to make tools