High-Bandwidth Version
Search Evolution  
Click to return to the Evolution Home Page
darwin change extinction survival sex humans religion
What Killed the Dinosaurs?

Introduction | Asteroid Impact | Volcanism | Mammal Competition | Continental Drift | Conclusion

Hypothesis: Continental Drift

It's difficult to imagine a process more gradual than continental drift. But some scientists say that, slow or not, this repositioning of the world's landmasses was disastrous for dinosaurs.

As continents heaved upward, pushed by the movement of tectonic plates, ocean currents were redirected and global sea levels fell. The Interior Seaway, for example, which once divided North America in half, simply drained away as the Colorado Plateau rose thousands of feet.

According to this hypothesis, climates in many parts of the world became drier and cooler. The resulting ecosystems produced less food than the environments in which dinosaurs evolved and were unable to sustain them.

Evidence for the Continental Drift Hypothesis

Fossil Record
A gradual decline in the number of dinosaur species would likely mirror an equally gradual cause of their ultimate extinction. Conversely, a sudden "now you see them, now you don't" end to the dinosaurs implies a catastrophic cause. Depending on location and interpretation, the fossil record seems to say different things.

According to some scientists, fossil evidence clearly shows a decline in the number of dinosaur species for several million years leading up to the end of the Cretaceous.

Sea Level
The presence of 65- to 70-million-year-old fossilized ocean creatures thousands of feet above present-day sea level strongly suggests that ocean levels fell dramatically as the Cretaceous period came to a close.

According to many scientists, continental drift and ocean regression would have caused continents to become drier, cooler, and less hospitable to dinosaur life than they had been previously.

-> Will we ever really know what killed the dinosaurs?

Introduction | Asteroid Impact | Volcanism | Mammal Competition | Continental Drift | Conclusion

  related web activities  
Riddle of the Bones
Piece together clues about our early ancestors.
A Modern Mass Extinction?
Are we in the midst of one? And if so, did we trigger it?
Deep Time
Explore 4 billion years of life on Earth.
  related topics  
  Deep Time/History of Life  
  What Is Science?  
  Evidence for Evolution  
Videos Web Activities Site Guide About the Project FAQ Glossary Site Map Feedback Help Shop