Chapter 3c Ocean Basin Evolution

Stages of Ocean Basin Evolution

Embryonic

rift valley forms as continent begins to split

Great Rift Valley, Eastern Africa

Juvenile

sea-floor basalts begin forming as continental sections diverge

Red Sea

Mature

broad ocean basin widens, trenches develop and subduction begins

Atlantic Ocean

Declining

subduction eliminates much of sea floor and oceanic ridge

Pacific Ocean

Terminal

narrow ocean basin, possibly shallowing because of sediment input

young mountain ranges along flanks

Mediterranean Sea, Persian Gulf

Continental Collision

last of the sea floor is eliminated and continents collide,

forming a continental mountain chain.

Himalayas and Tibetan Plateau

The Red Sea – Forming a new ocean basin

Life Cycle of an Ocean

Types of Faults

Extensional – pulling apart, normal fault

Compressional – pushing together, thrust fault

Transform – sliding past laterally

The type of faults show the direction of stress

Stages of Ocean Rifting

Embryonic

regional uplift, extensional faulting

rift valleys on continent

East African Rift Valley

Juvenile

rift valley deepens and is flooded by seawater

spreading begins (mid-ocean ridge forms)

Sequence of opening a new ocean basin:

Dead Sea Rift (north end of Red Sea)

Red Sea (true ocean basin, but still narrow)

Gulf of Aden (becoming an open ocean basin)

Mature

ocean basin with spreading center & continental margins

Atlantic Ocean

Declining

dominated by convergence (subduction)

trenches / volcanic island arcs / coastal mountain ranges

Pacific Ocean

Terminal

convergence – continental blocks squeeze ocean basin

collision / regional uplift / narrow, closing seas

Mediterranean Sea

Persian Gulf – small remnant of ancient Tethys Sea, almost completely closed

Suturing

continental collision with regional uplift

high mountain belts form

Himalayas and Tibetan Plateau

Rifting of the Red Sea

modern, active process

extension of the MOR spreading center in the Indian Ocean

(Carlsberg Ridge)

Rifting of Pangaea

In the beginning of the Jurassic,

about 200 million years ago,

the same set of processes began

rifting Pangaea to form the Atlantic Ocean.

Afar Triple Junction

Extensional Faulting in the Afar Rift

Axial Volcanoes in the Afar Rift

Regional Basalt Intrusion – Somalia

East African Rift

Lake Tanganyika

Mount Kilamanjaro

Northern Red Sea

showing the Nile Valley, Nile Delta, and Sinai Peninsula

The Dead Sea and Dead Sea Rift

Closure Part I

/

Peruvian Trench

Chilean Coast

showing Andes Mountains

Closure Part II

Tethys Seaway

Persian Gulf and the Strait of Hormuz

Indian subcontinent, geologic provinces

Indian Plate Collision from Space

Himalayan Front from Space

View into the Himalayas

Tectonic map of region around Indian Ocean

All stages in ocean evolution are found here

Western U.S. – Great Basin

Extension (spreading) of the Basin and Range province