•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

•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

•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

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

Orogenic Belts

•Folded rocks in the Alps of SwitzerlandAlps

•The Indian plate moved northward for millions of years until it collided with the Eurasian plate

India Collides with Eurasia

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 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.

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://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

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▫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