Plate Tectonics Explained

Summary

The concept of continental drift, once doubted, is now proven by evidence showing Earth's crust is divided into tectonic plates. These plates move due to mantle convection, but also self-drive through a process where oceanic plates subduct under thicker plates, pulling them along. This subduction also fuels mantle convection, making seafloor crust an integral part of the Earth's dynamic movement.

Takeaways

• 🌏 The concept of continental drift has been around for over 200 years but was widely accepted by geologists in the 1960s with substantial evidence.
• 🔍 Tectonic plates are fragments of Earth's crust that move, and this motion is now tracked with millimeter precision from space.
• 🌌 The common explanation for plate movement is that they are carried by currents in the upper mantle, which is a slowly flowing layer of rock beneath the crust.
• 🔄 The upper mantle's convective currents cause plates to converge or diverge, with hot rock rising from the core and sinking back down as it cools.
• 🏎 Some plates, like the Nazca plate, move faster than the mantle currents beneath them, indicating additional forces at play.
• 🔗 Tectonic plates can actively pull themselves, especially when an ocean plate subducts under another plate, causing the leading edge to sink and pull the rest of the plate.
• 🗺 Deep ocean trenches visible on Google Earth are evidence of subduction zones where ocean crust is being pulled under continental plates.
• 🔧 Subducting oceanic plates influence mantle convection by blocking sideways rock flow, forcing it to turn downward and sink.
• 🌐 The sinking slabs of ocean crust create a suction force that aids in pulling mantle material, contributing to the conveyor belt-like motion of the plates.
• 🏞 In contrast to the dynamic movement of oceanic plates, continental plates are described as passive, moving more like baggage being carried along.
• 🔮 The script highlights the complex interplay between tectonic plates and the mantle, challenging the simplified view of passive plate movement.

Q & A

How old is the concept of continental drift?

The concept of continental drift is at least 200 years old.

When did most geologists start to believe in the theory of continental drift?

Most geologists started to believe in the theory of continental drift in the 1960s when mounting evidence made it clear.

What is the Earth's crust broken up into?

The Earth's crust is broken up into fragments known as tectonic plates.

How is the motion of tectonic plates tracked today?

The motion of tectonic plates is tracked with millimeter precision from space.

What is the simplified explanation for the movement of tectonic plates?

The simplified explanation is that tectonic plates are carried along on currents in the upper mantle, with converging currents driving plates into each other and diverging currents pulling them apart.

What happens when hot mantle rock rises from the Earth's core?

Hot mantle rock from the core rises and moves along under the crust until it grows cool and heavy, then sinks back down.

Why can't tectonic plates be passively riding the mantle currents like suitcases?

Tectonic plates can't be passively riding because some plates are moving faster than the currents underneath them.

What is an example of a tectonic plate moving faster than the underlying mantle current?

The Nazca plate, off the west coast of South America, moves eastward at about 10cm per year, while the mantle underneath it moves at just five.

How do some of Earth's plates move faster than the currents beneath them?

Some plates are pulling themselves, especially when an ocean plate collides with another plate and bends and slides under it.

What can be observed in Google Earth to identify where plates are pulling themselves?

In Google Earth, the deep, narrow ocean trenches visible off the coasts of some continents and island chains mark where ocean crust is plunging downward.

How do sunken slabs of ocean crust affect the convection in the mantle?

Sunken slabs of ocean crust block the sideways movement of rock, forcing it to turn downward and sink, and eventually creating a suction force that pulls mantle material along behind it.

What is the difference between the behavior of seafloor crust and continental plates in terms of tectonic movement?

Seafloor crust is more like part of the conveyor belt, actively participating in the movement, while continental plates are more like baggage, passively being moved.