East African Rift 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 Africa Rifting 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 African Rift 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

Orogenic Belts Circum-Pacific orogenic belt and the Alpine- Himalayan orogenic belt are the sites of most recent geologic and orogenic activity

Alps Folded rocks in the Alps of Switzerland

India Collides with Eurasia The Indian plate moved northward for millions of years until it collided with the Eurasian plate

High pCO2 during early Eocene Large-scale volcanism Giant’s Causeway in N. Ireland Early Tertiary age

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 formation Isolation of Arctic Ocean; sea-ice formation 2. Orogenesis Isolation 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.

Decreasing pCO2 after ~50 Ma Collision began ~50 Ma Increased weathering = Atm. CO2 decrease CaSiO3 + CO2 = CaCO3 + SiO2

Neogene Life Isolation of Antarctica led to glaciation Global cooling

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

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

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

Ice Age—Pleistocene Climate began to cool and new animals evolved Mammoth Saber-toothed cat Modern Humans – Homo Sapiens

Baby Mammoth http://img.rian.ru/images/10412/88/104128804.jpg http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/5262616/Secrets-of-37000-year-old-baby-mammoth-revealed.html

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

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

Holocene Epoch Includes present Great Lakes filled 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