An interactive presentation on continental drift and plate tectonics
The Earth's crust is divided into large pieces called tectonic plates. These plates float on the semi-fluid mantle beneath them and move very slowly over time. This movement is responsible for many of Earth's major geological features and events, including mountains, earthquakes, and volcanoes.
In this presentation, we'll explore:
The theory of continental drift was first proposed by Alfred Wegener in 1912. He noticed that the continents, particularly South America and Africa, appeared to fit together like puzzle pieces. Wegener suggested that all continents were once joined in a single supercontinent he called "Pangaea" (meaning "all lands" in Greek).
Initially, Wegener's theory was rejected by the scientific community because he couldn't explain how the continents moved. It wasn't until the 1950s and 1960s that new evidence from seafloor spreading and paleomagnetism led to the development of plate tectonics theory, which provided the mechanism for continental drift.
About 335 million years ago, Earth's continents began coming together to form the supercontinent Pangaea. By 250 million years ago, Pangaea was fully formed. Around 200 million years ago, it began to break apart, with the continents slowly drifting to their current positions.
Tectonic plates interact with each other in three main ways, creating different types of boundaries. Each type of boundary produces distinctive geological features and phenomena.
At divergent boundaries, tectonic plates move away from each other. As the plates separate, magma rises from the mantle to fill the gap, creating new crust. This process is called seafloor spreading when it occurs in oceans, and rifting when it occurs on continents.
At convergent boundaries, tectonic plates move toward each other. What happens depends on the type of crust involved:
At transform boundaries, plates slide horizontally past each other. This movement can cause earthquakes as pressure builds up and is suddenly released. No new crust is created or destroyed at transform boundaries.
The movement of tectonic plates is driven by convection currents in the mantle. Heat from the Earth's core causes material in the mantle to rise, while cooler material sinks. This creates a circular flow that drags the plates along.
Plate tectonics is a fundamental theory that helps us understand many of Earth's features and processes. By studying how plates move and interact, scientists can: