Dinosaurs lived during a time when Earth’s continents were arranged very differently from today. Early in the Mesozoic Era, most land was joined into the supercontinent Pangaea, which let many animals spread across huge connected habitats. As Pangaea broke apart, oceans opened, climates shifted, and dinosaur populations became separated.
This helps explain why similar fossils are found on continents now divided by wide oceans.
Understanding Dinosaurs & Paleontology: Continental Drift and Dinosaurs
Earth’s outer shell is broken into huge slabs called tectonic plates. Continents ride on these plates, but the plates are not floating freely on liquid rock. They move slowly over a hot, deformable layer deep below the surface.
New ocean floor forms at long cracks on the seafloor called mid ocean ridges. As fresh rock is added, older seafloor is pushed outward. In other places, dense oceanic crust bends downward and sinks beneath another plate.
These processes change the size of ocean basins and move continents over millions of years. A plate may travel only a few centimetres in a year, yet that becomes thousands of kilometres over geologic time.
Moving land changes far more than a map. It can build mountain ranges where plates collide. Mountains affect wind and rainfall, creating wetter slopes on one side and dry regions on the other.
A continent drifting toward a pole can become cooler, while one near the equator may have strong seasonal rains. Sea level can rise or fall as ocean basins change shape. Shallow seas may cover parts of continents, then disappear later.
Each change alters the plants available for plant eaters, the shelter available for small animals, and the hunting grounds available for predators. Dinosaurs therefore responded to shifting environments, not simply to changing coastlines.
Scientists test past continental positions using several kinds of evidence. Rocks can preserve the direction of Earth’s magnetic field when they formed. Since the magnetic poles have changed position many times, magnetic patterns in rocks help reconstruct plate movement.
Matching rock layers and mountain belts on separate continents provide another clue. Fossils are especially useful when the same species, or closely related species, occur in regions that are now far apart. Researchers must still consider other possibilities.
Animals could have crossed temporary land bridges, island chains, or narrow seas. Fossil evidence works best when it agrees with rock evidence, fossil ages, and a realistic route for movement.
This topic connects to places students know today. Earthquakes, volcanoes, deep ocean trenches, and mountain belts mark active plate boundaries. The Atlantic Ocean is still widening in some areas as new seafloor forms, so North America and Europe are moving apart very slowly.
In class, pay close attention to the difference between continental drift and plate tectonics. Continental drift describes the movement of continents. Plate tectonics is the wider explanation involving whole plates and their boundaries.
When estimating motion, use speed equals distance divided by time and keep units consistent. Most importantly, think in long timescales. A change too small to notice in one lifetime can reshape climates, habitats, and the history of life over tens of millions of years.
Key Facts
- Pangaea existed as a supercontinent during the late Paleozoic and early Mesozoic eras.
- The Mesozoic Era lasted from about 252 million years ago to 66 million years ago.
- Plate speed can be estimated with v = d/t, where v is speed, d is distance, and t is time.
- Continental drift is driven by plate tectonics, including seafloor spreading, subduction, and mantle convection.
- Similar dinosaur fossils on different continents can show that those landmasses were once connected or much closer together.
- Geographic isolation after continental breakup can lead to different evolutionary paths in separated dinosaur populations.
Vocabulary
- Pangaea
- Pangaea was a supercontinent that joined most of Earth’s landmasses into one large land area before it began breaking apart.
- Continental drift
- Continental drift is the slow movement of continents across Earth’s surface over geologic time.
- Plate tectonics
- Plate tectonics is the theory that Earth’s outer shell is divided into moving plates that interact at their boundaries.
- Fossil correlation
- Fossil correlation is the use of similar fossils in different places to match rock layers and reconstruct past environments.
- Vicariance
- Vicariance is the separation of populations by a geographic barrier, such as a new ocean or mountain range, which can affect evolution.
Common Mistakes to Avoid
- Thinking the continents moved quickly enough for dinosaurs to notice is wrong because plate motion is usually only a few centimeters per year.
- Assuming identical fossils on separate continents always mean dinosaurs swam across oceans is wrong because the landmasses may have been connected when those animals lived.
- Treating Pangaea as the setting for all dinosaurs is wrong because Pangaea began breaking apart during the Mesozoic, so later dinosaurs lived on separated continents.
- Using modern maps to judge dinosaur habitats without changing continent positions is wrong because coastlines, climates, and distances were very different in the past.
Practice Questions
- 1 South America and Africa are now about 2,800 km apart at one matching coastline. If that separation developed over 140 million years, what was the average separation speed in cm/year?
- 2 A dinosaur fossil is dated to 150 million years ago. How many million years before the end of the Mesozoic Era at 66 million years ago did that dinosaur live?
- 3 Two closely related dinosaur species are found in rocks of the same age in South America and Africa. Explain how continental drift could account for both their similarity and their later differences.