What are Tectonic Plates?

“Plate tectonics” is the theory that Earth’s outer shell is divided into large slabs of solid rock, called “plates,” that glide over Earth’s mantle, the rocky inner layer above Earth’s core.

The Earth’s solid outer layer, which includes the crust and the uppermost mantle, is called the lithosphere. Wikipedia says that it is 100 kilometres thick, but I think they meant to say 1 million. The Earth’s mantle contains a large amount of hot rock that keeps the Earth’s surface hot. Beneath this hot, rocky layer is the asthenosphere — a relatively soft, liquid-like material that can easily deform and flow. The Earth’s tectonic plates are lubricated by the fluid called a mantle plume, which allows them to move around.

How plate tectonics works

How Do Plates Move?

The driving force behind plate tectonics is the convection of hot rocks in the mantle. Scientists have long known that there are differences in the crust of the Earth – the upper part of the solid Earth, where we live. But they’ve been puzzled by why those differences happen.

Meanwhile, geologists think of the plates that cover Earth’s mantle as bumper cars, constantly crashing into one another. Sometimes the plates stick together, and sometimes they don’t, depending on the tectonic stresses. Scientists call the places where plates meet and divide as plate boundaries. They’re called “jellyfish,” and some of them look kind of like giant sea turtles.

This is an interesting example of a glacier growing faster than it erodes. This is true for glaciers in general, but in the Alps in particular. In fact, the Alps are still growing faster than they’re eroding!

There are three ways in which plate boundaries meet, and each one triggers a unique geological feature.

Convergent boundaries happen when plates collide with each other. Where those plates meet, Earth’s crust crumbles and buckles into mountain ranges. For example, the Indo-Asian Plate collided about 55 million years ago to create the Himalayas, which lie between India and Asia. You’re not the only one who’s interested in learning more about this trend. Many are excited to learn what it means. The Swiss Alps are being lifted faster than they are being lowered through erosion. Because the Alps are rising, the researchers say they’re growing every year. Even though a mountain’s mass becomes too large to resist gravity, it won’t grow because gravity is a law of nature. Water is also essential for growth, but if the water is contaminated with sediment, it can cause damage to plants that inhibit their ability to absorb nutrients and photosynthesis. Erosion can be a problem in areas with heavy rainfall or where there are a lot of rocks, but it’s usually not an issue for the plant itself.

But the convergence of plates does not always produce an upward thrust. Occasionally, an ocean plate (which is made of denser rock than landmasses) collides with a continental plate, which causes it to “subducts” or dive beneath the other plate. This descends into the Earth’s mantle, the layer underneath the crust, and melts in the mantle’s hot magma, and is spewed out in a volcanic eruption. There are many spectacular volcanoes located along the subduction zones, like the “Ring of Fire” that surrounds the Pacific Ocean.

When two tectonic plates converge they are said to “converge”. This occurs in a deep trench, such as the Mariana Trench in the North Pacific Ocean, the world’s deepest point. Water is not always smooth and quiet, but if you look closely, you’ll see that there are many types of collisions. Some of these collisions can lead to underwater volcanoes.

There is a lot of activity and tectonic activity along this boundary. Tectonic plates are those that are moving apart or pulling apart. This part of the plate boundary is where the Pacific Plate is pulling away from the North American Plate. This is the motion that creates giant troughs, such as the East African Rift. The ocean’s mid-ocean ridge system is like a giant conveyor belt, pushing up the floor of the ocean. It’s when magma from Earth’s mantle well up to form new ocean crust and push apart the plates that the earth creates new land and pushes continents apart. Some underwater mountains and volcanoes form islands, and in these places, there are new ecosystems that you can’t find anywhere else in the world. For example, the Mid-Atlantic Ridge runs directly through Iceland.

The final kind of plate boundary is the transform boundary, which occurs when the plates move laterally (sideways) relative to each other. Plate tectonics is a critical part of an earthquake, and it can trigger an earthquake from very far away, over huge distances. A transform fault is a zone where a plate boundary is a kind of a transform boundary, where the plates grind past each other in a mostly horizontal motion. It’s famous for the San Andreas fault in California.

The Pacific tectonic plate is moving toward the North American plate at a rate of one to 2 inches (3 to 5 centimetres) per year, as reported by National Geographic. It’s not as fast as your fingernails grow, but it sure is a lot faster than I can type out this answer.

How many plates are there?

When the Earth was first formed, its plates were flat, and so they remained relatively smooth. But over time, these plates became cracked, and new cracks formed. These cracks formed and broke off at different times, which created huge differences in distance between each fracture. The result? Tectonic plates are now thousands of kilometres apart. 

According to World Atlas, there are seven major plates, including the North American, Pacific, Eurasian, African, Indo-Australian, South American and Antarctic tectonic plates. But according to a 2012 article in Nature, there have been earthquakes over the last few decades that show that the Indo-Australian Plate has cracked over the last 10 million years, causing the creation of a separate Indian Plate and Australian Plate. That will make the number of major plates go up from seven to eight.

It may be the case that a new border or demarcation between nations does not qualify as a boundary. However, in this example, the Pacific Plate still remains the largest of all tectonic plates. It’s the largest island in the world, measuring 39,768,522 square miles (103,000,000 square kilometres) in size, and lies hidden beneath the ocean.

The list of Earth’s minor plates includes the Arabian Plate, the Caribbean Plate, the Cocos Plate, the Nazca Plate, the Philippine Plate, the Scotia Plate, and more. There are also many smaller plates throughout the world.

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