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Nazca plate

earth science Maturity 7-9 Next article →

The Nazca plate is a massive piece of oceanic crust. It is located in the eastern Pacific Ocean basin. It sits just off the west coast of South America. This tectonic plate is essential to understanding Earth's geology. Its constant movement shapes the landscape of entire continents. It is responsible for creating massive mountain ranges. It also drives powerful seismic activity in the region.

The plate moves toward the east at a very high speed. Scientists have measured this as 88 degrees of absolute motion. This makes it one of the fastest moving plates on Earth. As it moves east, it hits the South American plate. This creates a convergent boundary known as a subduction zone. The Nazca plate slides underneath the South American plate. This process forms the deep Peru–Chile Trench.

This subduction process causes the Andean orogeny. An orogeny is the process of mountain building. The pressure from the Nazca plate pushes up the Andes Mountains. The plate also exhibits unusual flat slab subduction. This means the plate slides at a shallow angle. As it sinks, the plate can tear and deform. This movement even affects the geography of Bolivia far to the east.

The Nazca plate has several different types of boundaries. On its western side, it meets the Pacific plate. This is a divergent boundary called the East Pacific Rise. To the south, it meets the Antarctic plate. This occurs at the Chile Rise, where seafloor spreading happens. Magma rises at this boundary to create new crust. To the north, it meets the Cocos plate. This boundary is called the Cocos–Nazca spreading centre.

There are special places where three plates meet. These are called triple junctions. One is the Chile triple junction near the Taitao Peninsula. Here, the Nazca, South American, and Antarctic plates join. Another junction exists near the coast of Colombia. This involves the Nazca, Cocos, and Pacific plates. These junctions often create small microplates. Examples include the Galapagos and Juan Fernandez microplates.

The history of this plate began millions of years ago. It was once part of the much larger Farallon plate. That plate broke apart about 23 million years ago. This event occurred during the late Oligocene period. The oldest rocks on the Nazca plate are 50 million years old. Subduction under South America actually began much earlier, about 140 million years ago. However, the high parts of the Andes formed later, around 45 million years ago.

This plate movement causes very large earthquakes. In 1960, the Valdivia earthquake hit southern Chile. It had a moment magnitude of 9.5. This remains the largest earthquake ever recorded on Earth. In 1994, an 8.2 magnitude earthquake occurred in Bolivia. This was a very strong earthquake for that depth. The plate also moves over hotspots. This creates volcanic islands and long chains of seamounts. The Carnegie Ridge is one such feature on the ocean floor.

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