A big piece of the Earth moved.
It slid under our land. It helped make big mountains. Now it is in small pieces. This helps us learn about our world. Do you like mountains?
A long time ago, a giant piece of the sea floor moved.
This big piece is called the Farallon plate. It slid under the land of North America. As it moved, it pushed bits of islands into our land.
This movement helped build the Rocky Mountains. Now, the big plate is in many small pieces.
These small pieces are still moving deep under the Earth. Scientists use special tools to see them. It is amazing how the Earth changes over time.
The Farallon plate was a huge piece of the ocean floor.
It lived a long time ago. It was one of three main plates in a giant ocean. This plate began to slide under North America. This set of steps is called subduction.
As it slid, it carried bits of islands with it. These bits are called terranes. They are pieces of land from far away. The Farallon plate pushed these terranes into North America. This helped make the Rocky Mountains.
The plate did not stay in one big piece. It broke into smaller parts. Some parts are still moving under the land today. We call these parts remnants. Scientists use a tool called seismic tomography to see them.
This tool uses waves to make a picture of the deep Earth. The waves move at different speeds through warm or cold parts. This helps us find the cold pieces of the old plate. It shows how the plate folded and bent deep underground.
The Farallon plate was a huge piece of the ocean floor.
It was one of three main plates in the Panthalassic ocean. This ocean was very large and existed a long time ago. The Farallon plate was connected to the Izanagi and Phoenix plates. These plates met at a special spot called a triple junction. This plate was very important for the history of our Earth. It helped shape the land we live on today.
This plate worked through a process called subduction. Subduction happens when one plate slides under another plate. The Farallon plate began to slide under the North American plate. This started near modern Utah as the land called Pangaea broke apart. As it moved, it carried bits of land called terranes. These terranes were island arcs and crust from far away. The plate pushed these pieces into the North American coast. This process helped build much of western North America.
Scientists study this plate using a tool called seismic tomography. This tool lets researchers see deep beneath the Earth's surface. It works by using seismic waves that travel through the ground. These waves move at different speeds depending on the temperature. The old Farallon plate is still quite cold deep underground. Because it is cold, it shows up clearly on the images. This helps scientists see how the plate folded and bent.
Scientists can even see where the plate might have torn apart.
There are many specific facts about how this plate moved. During one time, it had flat-slab subduction. This means the plate slid at a very shallow angle. This shallow movement helped create the Rocky Mountains far inland. Some studies suggest the plate broke into several different segments. These might include the Northern Farallon and Southern Farallon parts. A 2013 study even suggested other names like Mezcalera.
These details help us map the history of our planet.
We can still see the remains of this plate today. The Farallon plate broke into several smaller pieces. The Juan de Fuca, Cocos, and Nazca plates are remnants. Some of these pieces are still subducting under land today. The Juan de Fuca plate is under the northern coast. The Cocos plate is under Central America. The Nazca plate is under South America. These moving pieces are like the broken pieces of a giant puzzle.
The Farallon plate was a massive oceanic tectonic plate. It once moved through the ancient Panthalassic ocean. This plate was one of three major plates in that ocean. The other two were the Izanagi and Phoenix plates. These three plates met at a point called a triple junction.
The Farallon plate is named after the Farallon Islands near San Francisco. It played a huge role in shaping the western side of North America. Its movement helped build the land we see today.
Subduction is the main process that defined the Farallon plate. Subduction occurs when one tectonic plate slides beneath another. As the supercontinent Pangaea broke apart, the Farallon plate began to subduct. It moved under the west coast of the North American plate. At that time, the edge of North America was located near modern Utah.
As the plate moved, it acted like a giant conveyor belt. It carried pieces of land called terranes toward the continent. These terranes included island arcs and fragments of continental crust. These pieces were rifted off from other distant plates. When the Farallon plate subducted, it accreted these terranes to North America. Much of western North America is now made of these pieces.
Scientists cannot see the Farallon plate directly because it is underground. Instead, they use a method called seismic tomography. This technique allows researchers to image the deep Earth. It works by measuring seismic waves that travel through the planet. These waves move at different velocities depending on the temperature of the material.
The remnants of the Farallon plate are still much colder than the surrounding mantle. Because they are cold, they have not reached thermal equilibrium. This temperature difference makes the plate appear as a velocity anomaly. This allows scientists to see the submerged remains of the plate. They can observe how the plate folded and deformed deep below the surface.
One very important period was called flat-slab subduction. During this time, the plate subducted at a very shallow angle. Instead of diving deep, it slid closely against the bottom of the North American crust. This shallow angle had a massive effect on the landscape. It caused orogenesis, which is the process of mountain building. This specific type of subduction explains why the Rocky Mountains formed so far inland. Usually, mountains form near the edge of a plate. However, the flat Farallon plate pushed mountain-building forces much deeper into the continent.
Researchers have proposed several reasons for this flat subduction. One idea is that the North American plate moved faster, causing slab rollback. Another theory involves slab buoyancy. This buoyancy can be influenced by the presence of oceanic plateaus. These plateaus are areas of oceanic flood basalts. Some of these plateaus may have also been accreted to North America. There is also evidence that the slab suffered a tear. This means a piece of the plate broke off. This break may have created multiple remnants and helped form Laramide structures.
A 2013 study suggested the Farallon plate was even more complex. It proposed that the plate should be divided into several segments. These segments include the Northern Farallon and Southern Farallon. Other proposed names are Angayucham and Mezcalera. Under this model, North America overrode several subduction trenches. It also added microcontinents to its mass. This model provides a specific timeline for geologic events. For example, the Mezcalera promontory subducted around 165 to 155 million years ago. This event helped trigger the orogenesis of the Rocky Mountains.
Other major events followed this complex movement. Around 125 million years ago, island arcs collided with North America. This caused the Sevier orogeny. Between 124 and 90 million years ago, the Omineca magmatic belts formed. The Laramide orogeny occurred between 85 and 55 million years ago. This happened as buoyant terranes were added to the continent. Finally, the Siletzia and Pacific Rim terranes were accreted 55 to 50 million years ago. When the Siletzia archipelago lodged as a terrane, the trench moved west. This eventually created the modern Cascadia subduction zone.
The Farallon plate is now gone, but its pieces remain. It broke into several smaller, modern plates. These include the Juan de Fuca, Explorer, and Gorda plates. These plates are currently subducting under northern North America. The Cocos plate is subducting under Central America. The Nazca plate is subducting under South America. These remnants show how the ancient Farallon plate continues to influence our world. By studying these pieces, we understand the history of our planet's crust.
Where will your curiosity go next?
🖼️ Images & Media (6)
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.