Billions of years ago, Earth’s surface was an ocean of molten rock. As this boiling magma gradually cooled, a continuous shell of rock formed, with denser minerals coalescing toward the planet’s interior and less dense minerals rising to the surface.
“This is how plates formed on the surface of the Earth,” Katherine Reichert, a geophysicist at Woods Hole Oceanographic Institution in Massachusetts, told Live Science. “The plates are the crust, and underneath that is part of the mantle…underneath that is weak material.”
This weaker material is hotter and more mobile. Differences in strength between these layers cause the overlying plates to move and collide, diverge, and brush against each other. In these zones, cracks and mountains form, and volcanoes and earthquakes come to life.
But how many of these plates cover the Earth’s surface? The answer ranges from 12 to nearly 100, depending on how you look at it.
Related: What’s inside the Earth?
Saskia Goes, a geophysicist at Imperial College London, said most geologists agree that there are 12 to 14 “primordial” plates that cover most of the Earth’s surface. Each has an area of at least 7.7 million square miles (20 million square kilometers), with the largest being the North American, African, Eurasian, Indo-Australian, South American, Antarctic, and Pacific plates. The most monumental of these is the Pacific Plate, which spans a whopping 39.9 million square miles (103.3 million square kilometers), closely followed by the North American Plate, which spans 29.3 million square miles (75.9 million square kilometers).
“In addition to the very large seven; [plates]”There are five more somewhat smaller plates: Philippine Sea, Cocos, Nazca, Arabia, and Juan de Fuca,” Goes told Live Science. Some geologists count the Anatolian plate (part of the larger Eurasian plate) and the East African plate (part of it). “These plates are moving at distinctly different velocities than these main plates, so they are considered separate entities,” Goes said, adding that estimates for the main plates range from 12 to 14. explains the reason for this.
Things get even more complicated when we focus on plate boundaries. Plate tectonics breaks up plates into smaller pieces called microplates. They cover an area of less than 386,000 square miles (1 million square kilometers), and some scientists estimate there are about 57 of them on Earth. However, they are usually not included in world maps. This discrepancy reflects uncertainty about how they are formed.
“The number of microplates will depend on how different scientists choose to define them, and as more details emerge about where and how plate boundary deformation is localized. It will continue to change,” Goes said.
The movement of Earth’s plates creates some interesting scenarios as geologists understand this dynamic puzzle. The Pacific plate is probably the fastest, moving 2.8 to 3.9 inches northwest (7-10cm) per year) Reichert said.
“This fast movement is caused by surrounding subduction zones, also known as the Ring of Fire, where gravity is pulling the plates down onto the Earth,” she said, adding that the constant movement can swallow even continents. He added that there may be. “We think that sometimes continents form and pieces of them actually fall into the mantle,” Reichert said.
With such dramatic forces at play, it remains a mystery what Earth’s plate-covered surface will look like billions of years from now.