Plate boundary facts for kids

The Earth's surface isn't one solid piece! It's actually made up of huge, moving slabs called tectonic plates. These plates are always slowly shifting, and where they meet, we find what are called plate boundaries. These boundaries are super important because they are where most of the Earth's big geological events happen, like earthquakes and volcanoes. Think of them as the seams on a giant, slowly moving puzzle!

This picture shows the three main ways Earth's plates meet and interact.

Understanding Plate Boundaries

There are three main types of plate boundaries, each causing different geological features and events. All of these boundaries, except for "conservative" ones, are places where the Earth's crust is very active.

Spreading Plates: Divergent Boundaries

When two tectonic plates move away from each other, it's called a divergent boundary. As the plates pull apart, new molten rock (magma) rises from deep inside the Earth. This magma cools and forms new crust.

This process often creates rift valleys, which are long, narrow valleys formed when land sinks between two diverging plates. It can also build new mountain ranges, especially underwater. Many volcanoes are found along these spreading boundaries. A great example is the Mid-Atlantic Ridge, a huge underwater mountain range where the North American and Eurasian plates are pulling apart. On land, Africa's Great Rift Valley is another famous example of a divergent boundary.

Colliding Plates: Convergent Boundaries

A convergent boundary happens when two tectonic plates crash into each other. What happens next depends on the types of plates involved.

• Oceanic-Continental Collision: If an oceanic plate (which is usually denser) crashes into a continental plate, the oceanic plate often sinks beneath the continental plate. This process is called subduction. As the oceanic plate sinks, it melts, and this molten rock can rise to form chains of volcanoes on the continental plate. The west coast of the Americas is a good example, with many volcanoes and mountain ranges formed by this type of collision.
• Continental-Continental Collision: When two continental plates collide, neither plate is easily pushed down. Instead, the land crumples and folds, pushing up huge mountain ranges. This process is called orogeny (mountain building). The most famous example is when India collided with Asia, forming the mighty Himalaya Mountains. These collisions can also create deep valleys.

Sliding Plates: Transform Boundaries

At a transform boundary, two plates grind past each other horizontally. They don't move towards or away from each other, but rather slide sideways. This movement isn't smooth; the plates often get stuck. When the stress builds up too much, they suddenly slip, causing powerful earthquakes.

These boundaries are also known as fault boundaries. The San Andreas Fault in California, USA, is a well-known example where the Pacific Plate and the North American Plate are sliding past each other. While volcanoes are less common directly on these faults, the intense friction and stress can sometimes lead to volcanic activity nearby.

Images for kids

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  Plate motion based on Global Positioning System (GPS) satellite data from NASA JPL. Each red dot is a measuring point and vectors show direction and magnitude of motion.

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  Alfred Wegener in Greenland in the winter of 1912–13.

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  Global earthquake epicenters, 1963–1998. Most earthquakes occur in narrow belts that correspond to the locations of lithospheric plate boundaries.

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  Plate tectonics map