# Tectonic Plates: An Animated Video

A narrated eight\-minute animated film about tectonic plates: the cracked shell of the Earth, what moves it, the three kinds of plate boundary, the Ring of Fire and Pangaea

By William Anderson

Topic: Earth & Geography

[Open the interactive Jig](https://ask.jig.com/j/4TgdRaMcNCQi)

## Transcript

### 1. A planet in pieces

This is our home, seen from space\. It looks like one solid ball, but its rocky outer shell is cracked into giant pieces, like the shell of a boiled egg that has been tapped on a table\. Those pieces are called tectonic plates, and the glowing lines show where they meet\. There are about seven big plates and dozens of smaller ones\. And here is the amazing part: every one of them is moving, right now, under your feet\.

Drag anywhere to turn the Earth and look at it from another side\.

### 2. Inside the Earth

Let us slice the planet open\. On the outside is the crust, a thin skin of rock only 5 to 70 kilometres thick\. Below it lies the mantle, almost 3,000 kilometres of hot rock\. Deeper still is the outer core, liquid metal, and at the very centre a solid inner core of iron and nickel, about as hot as the surface of the Sun\. If the Earth were an apple, the crust would be thinner than its skin\.

The Earth is about 6,371 kilometres from its surface to its centre\.

### 3. Rafts of solid rock

A plate is more than the crust\. It is the crust plus the stiff top of the mantle, together called the lithosphere, about 100 kilometres thick\. Under it is the asthenosphere: rock so hot that it slowly flows, like very thick toffee, even though it is solid\. Heat from deep inside keeps the mantle churning, and the plates ride along\. Gravity helps too: the old, cold edge of a plate sinks and drags the rest of the plate behind it\.

The mantle is not a sea of lava\. It is solid rock that creeps a few centimetres a year\.

### 4. Pulling apart

Where two plates pull away from each other, hot rock rises into the gap, melts a little and hardens into brand new sea floor\. This makes a long underwater mountain chain called a mid\-ocean ridge\. The Atlantic Ocean widens this way by about 2\.5 centimetres every year, roughly as fast as your fingernails grow\. The stripes in the rock are a record of Earth's magnetic field flipping, mirrored on both sides like a barcode\.

This scene is a time\-lapse: each second here stands for hundreds of thousands of years\.

### 5. Diving down

When an ocean plate meets a continent, the heavier ocean plate bends and slides underneath\. This is called subduction\. Where it dives, it carves a deep trench in the sea floor\. As the sinking plate heats up, water squeezed out of it helps the rock above melt\. That melted rock, called magma, rises and builds a chain of volcanoes, like the Andes in South America\.

The deepest trench, the Mariana Trench, is about 11 kilometres deep\. Mount Everest would fit inside with room to spare\.

### 6. Making mountains

When two continents collide, neither one wants to sink: continental rock is too light\. So the crust crumples, folds and piles up, the way a rug wrinkles when you push it against a wall\. About 50 million years ago, India crashed into Asia, and it is still pushing north today\. That collision raised the Himalayas, the highest mountains on Earth, and they are still growing\.

Rocks near the top of Mount Everest contain fossils of sea creatures\. They formed on an ancient sea floor\.

### 7. Sliding past

Some plates neither crash nor pull apart\. They grind sideways past each other along a crack called a transform fault\. The rocks lock together and the strain slowly builds, bending the land like a stretched spring\. Then, suddenly, the rocks slip and the ground jumps: an earthquake\. Watch the stream and the fence: after the slip, they no longer line up\.

The San Andreas Fault in California is a famous example\. The two sides move about 5 centimetres a year on average\.

### 8. The Ring of Fire

Most earthquakes and volcanoes happen near plate edges\. Around the Pacific Ocean, plates dive under their neighbours on almost every side, making a horseshoe of trenches and volcanoes about 40,000 kilometres long\. It is called the Ring of Fire\. It holds about three quarters of the world's active volcanoes, and about nine in ten earthquakes happen along it\.

Mount Fuji in Japan, Mount St\. Helens in the United States and Cotopaxi in Ecuador all sit on the Ring of Fire\.

### 9. Pangaea

Now let us run the clock backwards\. About 200 million years ago, the continents were joined in one giant supercontinent called Pangaea\. Look how South America tucks into Africa like a jigsaw piece\. Then Pangaea split apart, and the Atlantic Ocean opened between them\. Scientists matched fossils of the same animals and plants on continents that are now oceans apart\.

Alfred Wegener suggested drifting continents in 1912\. Most scientists did not believe him until sea floor maps proved it in the 1960s\.

### 10. A world still moving

Today satellites measure the plates directly, and they keep moving at a few centimetres each year\. The plates build mountains, open oceans, feed volcanoes and recycle old sea floor back into the mantle\. Over millions of years, they reshape the whole face of the planet\. Hundreds of millions of years from now, the continents may even gather into a new supercontinent\. Our planet is alive, and it is still on the move\.

Pangaea was not the first supercontinent\. Others came before it, long ago\.