huddled together into a single landmass named Pangaea. Within a short span
of a few million years, black basalt erupted along a central spine of the super-
continent, eventually spreading over an area nearly the size of Australia. Soon
thereafter, the continents split apart along this axis and went their separate
ways, thereby opening up the Atlantic Ocean. This massive eruption, one of
the largest in Earth history, might have killed off much of the planet’s life and
led to the ascension of the dinosaurs as the rulers of the world.
Many flood basalts lie near continental margins, where great rifts began
to separate the present continents from Pangaea near the end of the Triassic.
These massive outpourings of basalt reflected one of the greatest crustal move-
ments in the history of the planet. The continents probably traveled much
faster than they do today because of more vigorous plate motions, resulting in
tremendous volcanic activity.
Triassic basalts common in eastern North America indicate the forma-
tion of a rift that separated the continent from Eurasia.The rift later breached
and flooded with seawater, forming the infant North Atlantic Ocean. The
Indian Ocean formed when a rift separated the Indian subcontinent from
Gondwana. By the end of the Triassic, India had drifted free and began its trek
toward southern Asia. Meanwhile, Gondwana drifted northward, leaving Aus-
tralia still attached to Antarctica behind in the South Polar region.
Huge basalt flows and granitic intrusions occurred in Siberia. Extensive
lava flows covered South America, Africa, and Antarctica as well. Southern
Brazil was paved with three-quarters of a million square miles of basalt, con-
stituting one of the largest lava fields in the world. Great floods of basalt,
upward of 2,000 or more feet thick, covered large parts of Brazil and
Argentina when the South American plate overrode the Pacific plate, and the
subduction fed magma chambers underlying active volcanoes. Basalt flows also
blanketed a region from Alaska to California.
Near the end of the Triassic, North and South America began to move
away from each other.India,nestled between Africa and Antarctica, began to
separate from Gondwana. The Indochina block collided with China. Addi-
tionally, a great rift began to divide North America from Eurasia. The rifting
of continents radically altered the climate and set the stage for the extraordi-
nary warm periods that followed.
After examining the early dinosaurs of the Triassic, the next chapter
explores the animals that took to the air during the Jurassic period.
TRIASSIC DINOSAURS