Historical Geology Understanding Our Planet\'s Past

apparently struck Earth with the explosive force of 100 trillion tons of dyna-

mite, turning the planet into an inhospitable world.Thus, the dinosaurs might

have been both created and destroyed by meteorites.

THE TETHYAN FAUNA

At the beginning of the Triassic, the Tethys Sea was a huge embayment sepa-

rating the northern and southern arms of Pangaea, which took the shape of a

gigantic letter C that straddled the equator (Fig. 141). Between the late Pale-

ozoic and middle Cenozoic, the Tethys was a broad tropical seaway that

extended from western Europe to southeast Asia and harbored diverse and

abundant shallow-water marine life. A great circumglobal ocean current that

distributed heat to all parts of the world maintained warm climatic conditions.

The energetic climate eroded many high mountain ranges of North America

and Europe down to the level of the prevailing plain.

Early in the Tr iassic, ocean temperatures remained cool following the

late Permian ice age. Marine invertebrates that managed to escape extinc-

Figure 141The Tethys
Sea nestled between
North and South Pangaea
280 million years ago.

Historical Geology

EUROPE

and

ASIA

AFRICA

Tethys Sea

ANTARCTICA

INDIA

AUSTRALIA

SOUTH

AMERICA

NORTH

AMERICA