Continental drift is the large-scale horizontal movement of continents relative to one another and relative to ocean basins over one or more episodes of geological time. This concept is an important precursor to developing the theory of plate tectonics contained therein.
A geological episode or event is defined as an observable event in which one or more geological processes act to change the geological unit. Geologic time scales are divided into four-time spans, namely:
Read on for some thoughts on why this can be a daunting topic for teachers and students alike, five suggestions to help change that, and thoughts on why a virtual lab could make things easier.
There are three reasons in particular why Continental Drift Theory can be difficult, even for the most diligent of students.
Since continental drift occurs underground, students have a hard time understanding it. All the mechanisms responsible for plate movement are invisible to humans. This poses a huge challenge and thus makes learning ambiguous for students.
The coasts of South America and Africa come together like a giant jigsaw puzzle. Cartographers noticed the geometric fit of the continents of the South Atlantic centuries ago. In 1915, Alfred Wegener proposed the first scientific hypothesis based on these observations. According to his theory of continental drift, the continents have changed their relative positions during geological time.
Beaches and sea levels have changed over millions of years. Today, there are overlaps and gaps in some parts of the continental jigsaw puzzle. In short, the submerged continental shelf is more suitable than the current coast. In addition, Wegener found other evidence to support his theory.
Climatic evidence for continental drift is as follows:
The geological record contains information about the past climatic conditions of a particular continent. Since the climate is related to Earth's latitude, this can provide evidence for the continental drift theory. Previous ice age events have left traces in the form of sedimentary deposits or special landforms (e.g. U-shaped valleys). Glacial streaks even indicate the direction of the ice flow. The extent and distribution of such deposits tell us where past climatic conditions were cold enough for glaciation. Today, evidence of a major glaciation some 300 million years ago is scattered across various latitudes and all southern continents, including India and Australia. In today's warm climate, no ice sheets can form there. So Alfred Wegener knew that the continents must have been at higher latitudes, closer to the South Pole, where the climate was colder.
Figure 2: Distribution of ancient glacial deposits; climatic evidence for the continental drift theory.
Fossils are important evidence for the theory of continental drift. Fossils tell us about the distribution of species millions of years ago and what their habitats were like when the animals lived, such as the climate. Alfred Wegener found the same fossils (e.g. Mesosaurus) on all the now-distant southern continents. The southern continent was once united in the supercontinent Pangea. According to the continental drift theory, they were very close together and had the same climate before drifting apart. People who doubt the continental drift theory try to find other explanations for these fossils. But the independent evolution of the same species on different continents contradicts Darwin's theory of evolution. Swimming across the Atlantic is not a viable option. Mesosaurus lived only in fresh water and other species could not swim at all. And it is highly unlikely that an animal would have traveled such a long distance across a land bridge.
Figure 3: Distribution of four different fossils across the southern continents as evidence for the continental drift theory.
With these points in mind, here are five things you can consider introducing into your continental drift theory lessons to make them more engaging, approachable, and enjoyable to teach for you and to learn for your students.
Alfred Wegener, a German meteorologist, proposed the first major detailed and comprehensive theory of continental drift in 1912. Combining vast amounts of geological and paleontological data, Wegener postulated that for most of the geological time there was only one continent, which he called Pangaea.
The appearance of Cratonic rocks on earth: The geological record contains clues about the location and arrangement of continents that are much older than fossils or glacial deposits. The continental core is made up of cratons, some of the oldest rocks found on Earth. Some of the cratons are more than 4 billion years old. The occurrence of cratons coincided on various continents on both sides of the Atlantic, for example in South America and Africa.
Evidence of tectonic activities around the earth: Alfred Wegener also discovered a tectonic match in addition to this geological match. He noted that several mountains on both sides of the North Atlantic formed at about the same time. The Appalachian Mountains in the US and the Scottish Highlands in Europe are about the same age. Wegener concluded that they formed during a single orogeny event some 400 to 480 million years ago. When the continents were rearranged without what is now the North Atlantic between them, these mountain ranges were flattened into one giant mountain belt.
Figure 4: The distribution of cratons (Southern Hemisphere) and mountain ranges (Northern Hemisphere) serves as geological evidence for the continental drift theory.
The original continental drift theory had no explanation for the mechanism behind continental movement. In the 1960s, some scientists discovered processes such as seafloor spreading and mantle convection. They can explain the movement of continents and tectonic plates in the past, supporting Wegener's hypothesis.
Today, the theory of plate tectonics has replaced the theory of continental drift. We know that not just one continent is moving but also entire tectonic plates. Scientists use satellite observation methods to track plate movements. GPS measurements show that the rate at which the Earth's ocean floor is spread varies, but they all move within a few centimeters per year.
Figure 5: Satellite data showing the current direction and rate of movement for all major tectonic plates.
Carton- Cratons are the old and stable parts of the continental lithosphere, consisting of the Earth's two uppermost layers, the crust and the uppermost mantle.
Fossil- Fossils are the preserved remains, traces, or traces of creatures that have lived from the past geological epoch
Tectonic activities- This refers to the forces or conditions on earth that cause the movement of the earth's crust.
Figure 6: An image extracted from the continental drift theory simulation from Labster. The simulation is useful for High School and University/College courses
A unique way to teach Continental Drift Theory is through a virtual laboratory simulation. At Labster, we’re dedicated to delivering fully interactive advanced laboratory simulations that utilize gamification elements like storytelling and scoring systems, inside an immersive and engaging 3D universe.
Check out the Labster continental drift theory simulation that allows students to learn about continental drift theory through active, inquiry-based learning. In the simulation, students will piece together the jigsaw puzzle of continental drift by investigating different forms of evidence and unraveling the story of how the continents have moved over millions of years.
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