|How to submit educational material to Enchanted Learning| |THE
CRETACEOUS-TERTIARY ASTEROID THEORY| Most of the dinosaurs went
extinct long before the catastrophic mass extinction at the end
of the Cretaceous period, 65 million years ago. Background
extinctions and many minor extinctions accounted for the
disappearance of most of the dinosaur species. During the late
Cretaceous, the number of dinosaur families was dwindling. The
latter part of the Cretaceous period was a time of high tectonic
activity (continental drift) and accompanying volcanic activity
. The supercontinent Pangaea was splitting up and the continents
were taking on their modern-day forms. The separation of
Laurasia and Gondwana was complete. Many mountain ranges were
formed . The sea levels rose during the mid-Cretaceous, covering
about one-third of the land area. Toward the end of the
Cretaceous, there was a drop in sea level, causing land exposure
on all continents, more seasonality, and greater extremes
between equatorial and polar temp