Plate tectonics and continental drift are related concepts that explain the movement and evolution of the Earth’s crust. In this article, we will explore what these terms mean, how they are connected, and what evidence supports them.
What is Continental Drift?
Continental drift is the hypothesis that the continents have moved over geologic time relative to each other. According to this idea, millions of years ago, there was one giant supercontinent called Pangea and one huge ocean called Panthalassa. Over time, Pangea split apart into the seven continents and formed the Earth’s oceans we have today.
The idea of continental drift was first proposed by Abraham Ortelius in 1596 and independently developed by Alfred Wegener in 1912. Wegener noticed that the continents of South America and Africa looked like they would fit together remarkably well, like pieces of a puzzle. He also found similar fossils, rocks, and climatic evidence on different continents, suggesting that they were once joined.
However, Wegener’s theory was widely ridiculed and rejected by most scientists at the time, because he could not explain what caused the continents to move or how they could plow through the ocean floor.
What is Plate Tectonics?
Plate tectonics is the science that studies the movement of the continents as they ride on plates of the Earth’s lithosphere. The lithosphere is the rigid outer layer of the Earth that consists of the crust and the upper mantle. The lithosphere is broken into several pieces called tectonic plates, which are in constant motion due to convection currents in the underlying asthenosphere, a layer of hot and plastic rock.
Plate tectonics also explains how the plates create volcanoes, earthquakes, mountain ranges, and oceans by interacting at different types of boundaries: convergent, divergent, and transform. Convergent boundaries occur when two plates collide, resulting in subduction (one plate sinks under another) or uplift (both plates rise). Divergent boundaries occur when two plates move apart, creating new crust at mid-ocean ridges or rift valleys. Transform boundaries occur when two plates slide past each other horizontally, causing faults and earthquakes.
Plate tectonics emerged as a more comprehensive theory in the 1960s, when new technologies and discoveries provided more evidence for continental drift and seafloor spreading. Seafloor spreading is the process by which new oceanic crust is formed at mid-ocean ridges and moves away from them. Scientists found that the seafloor was not uniform, but had alternating stripes of magnetic polarity that matched the reversals of Earth’s magnetic field over time. They also found that the seafloor was younger near the ridges and older near the continents, confirming that new crust was being created and recycled.
How are Plate Tectonics and Continental Drift Related?
Plate tectonics and continental drift are related because they both describe how the Earth’s surface changes over time due to the movement of tectonic plates. Plate tectonics incorporates and expands on continental drift by providing a mechanism for how and why the continents move. Continental drift is a consequence of plate tectonics, as the continents are part of larger plates that drift along with them.
Plate tectonics and continental drift are supported by various types of evidence, such as:
- The shape and fit of the continents
- The distribution and similarity of fossils, rocks, and climatic zones across continents
- The age and magnetic patterns of the seafloor
- The location and frequency of earthquakes and volcanoes along plate boundaries
- The GPS measurements of plate motions
Plate tectonics and continental drift are related concepts that explain the movement and evolution of the Earth’s crust. Plate tectonics is a more comprehensive theory that incorporates continental drift as a consequence of plate motions driven by convection currents in the asthenosphere. Both theories are supported by various types of evidence from geology, paleontology, geophysics, and geodesy.