Plate tectonics is a theory that deals with the dynamics of Earth’s outer shell, the lithosphere, and it revolutionized Earth sciences by providing a consistent framework for understanding mountain-building processes, volcanoes, earthquakes, and the evolution of Earth’s surface and reconstructing past continents and oceans.
Plate Tectonics Features Explained
The lithosphere (outer crust) is made up of tectonic plates that move on top of a heated, moving mantle layer known as the asthenosphere. Convection currents created by the heat in the asthenosphere lead tectonic plates to move several millimeters each year relative to one other. A “plate boundary” occurs when two tectonic plates collide. Plate borders may be divided into three categories, each of which is linked to the creation of different geologic phenomena.
A convergent plate boundary is formed when two tectonic plates clash. Subduction is a process in which one of the converging plates moves beneath the other. Deep trenches are common characteristics created when tectonic plates are subducted, and earthquakes occur often. Fluids are released from the rock when the sinking plate travels further into the mantle, causing the overlying mantle to melt. The new magma (molten rock) rises and may erupt violently, forming volcanoes and, in some instances, island arcs along the convergent boundary.
A diverging plate boundary occurs when two plates move away from one other. Magma rises from deep inside the Earth and erupts along these boundaries, forming a new crust on the lithosphere. Underwater, divergent plate borders produce oceanic spreading ridges, which are undersea mountain ranges. Volcanoes and earthquakes along oceanic spreading ridges are not as severe as they are at convergent plate borders, even though the process of building these mountain ranges is volcanic.
When tectonic plates travel horizontally past each other, the third type of plate boundary develops. A transform plate border is what this is called. Huge strains can force parts of the rock to shatter when the plates scrape against one other, resulting in earthquakes. Faults are the locations where these breakdowns occur. The San Andreas Fault in California is a well-known example of a transform plate boundary.
How Plate Tectonics Works
Convection in the mantle is the main factor underlying plate tectonics. Colder mantle rock dips as hot material near the Earth’s core rises. “It’s like a saucepan on the stove boiling,” Van der Elst explained.
Meanwhile, geologists envision the plates above the churning mantle colliding, sticking together, and then ripping apart like bumper cars. Plate borders are the points where segments meet and split, according to geologists. They’re said to wrap around the Earth like baseball seams.
Plate boundaries meet in three different ways, each of which results in a different geological aspect.
When two plates clash, they form convergent borders: the Earth’s crust cracks and collapses when those plates collide, forming mountain ranges. The Himalaya Mountains, for example, were formed when India and Asia merged 55 million years ago. Those mountains continue to rise as the mash-up progresses. According to research published in the journal Earth-Science Reviews in 2020, geologists revealed that the Swiss Alps are being raised faster than they are being eroded and are consequently expanding every year. When a mountain’s bulk grows too great to withstand gravity, however, it will stop growing. According to the University of Hawai’i at Manoa, erosion slows growth by wearing down mountains, but because mountains can grow quickly, erosion usually loses out.
Converging plates, on the other hand, don’t necessarily collide upward. When an ocean plate collides with a continental plate (which is comprised of denser rock than landmasses), the ocean plate “subducts” or dives beneath the continental plate. It then sinks into the Earth’s mantle, the layer under the crust, melts in the boiling magma of the mantle and erupts as a volcanic explosion. Along subduction zones, such as the Pacific Ocean’s “Ring of Fire,” many magnificent volcanoes may be seen.
A deep trench occurs when two oceanic plates collide, such as the Mariana Trench in the North Pacific Ocean, which is thought to be the world’s deepest point. Underwater volcanoes can form as a result of such collisions.
Divergent borders are tectonic boundaries where plates “diverge” or are pulled apart, as the term implies. On land, such as the East Africa Rift, this action generates massive troughs. The same mechanism in the ocean forms Mid-ocean ridges. At these ridges, hot lava from Earth’s mantle wells up, producing new ocean crust and pushing the plates apart. Along this seam, underwater mountains and volcanoes can rise, producing islands in some circumstances. The Mid-Atlantic Ridge, for example, goes all through Iceland.
Plate borders that shift sideways in respect to each other are the last type of plate boundary. Many earthquakes are caused by plate boundaries moving back and forth. The San Andreas Fault in California is a well-known example of a transform boundary. The North American and Pacific tectonic plates grind past each other in a mainly horizontal motion.
According to National Geographic, tectonic plates move at a pace of one to two inches (3 to 5 cm) each year. That’s how quickly your fingernails grow!
How Many Plates Are There?
Earth’s tectonic or lithospheric plates are broken into hundreds of bent portions due to their spherical shape. (Think of it as a cracked eggshell.) According to the USGS, each plate ranges in size from a few hundred to hundreds of kilometers in length and is classified as “major,” “minor,” or “micro” based on its size.
The North American, Pacific, Eurasian, African, Indo-Australian, South American, and Antarctic tectonic plates, according to World Atlas, are the seven main plates. According to a 2012 article in Nature, earthquakes in recent decades are proof that the Indo-Australian plate has broken during the last 10 million years, resulting in the formation of a distinct Indian Plate and an Australian Plate, bringing the total number of tectonic plates to eight.
The Pacific Plate remains the biggest of all tectonic plates, whether or not that new division counts as a border. It has 39,768,522 square miles (103,000,000 square kilometers) and is submerged beneath the sea.
The Arabian Plate, Caribbean Plate, Cocos Plate, Nazca Plate, Philippine Plate, Scotia Plate, and others are among Earth’s smaller plates. There are also a lot of smaller plates all around the planet.