Orogeny facts for kids

Mount Cook, New Zealand. This mountain is in the Southern Alps.

Even worn-down mountains show evidence of how they formed. This is Millook, Cornwall.

Orogeny is the scientific word for how mountains are built. It happens when huge pieces of the Earth's outer layer, called tectonic plates, move and crash into each other. This process is also known as orogenesis.

When these plates meet, the Earth's crust can get crumpled and pushed up. This forms the giant mountain ranges we see today. There are different ways mountains can form.

How Mountains Are Born

Mountains form in several ways, mostly due to the movement of Earth's tectonic plates.

Plates Colliding: The Big Squeeze

Most mountains form when two tectonic plates push against each other. Imagine two giant puzzle pieces slowly moving together.

• Oceanic Plate Meets Continental Plate: Sometimes, a heavy oceanic plate slides underneath a lighter continental plate. This is like one plate diving under another.
  • The Andes Mountains in South America formed this way.

• Two Continental Plates Collide: When two continental plates crash, neither can easily slide under the other. Instead, they crumple and fold upwards, like a rug being pushed from both ends.
  • The Alps in Europe and the mighty Himalayas in Asia (home to Mount Everest) are examples of this type of collision.

Hot Spots: Mountains from Below

Less often, mountains can form when a plate moves over a very hot spot deep inside the Earth's mantle. This hot spot melts rock, which then rises to the surface, creating volcanoes or pushing up the land.

• The Hawaiian islands are a chain of volcanoes formed as the Pacific plate moved over a hot spot.
• Yellowstone National Park in the United States also sits over a hot spot.

Delamination: A Deep Lift

Another way mountains can rise is through a process called delamination. This happens when a heavy, unstable part of the Earth's deep crust or upper mantle breaks off and sinks. When this heavy part drops, the lighter material above it can float up, causing the land to rise.

• The Sierra Nevada mountains in California are thought to have formed partly due to delamination.

Rifting Apart: Stretched and Lifted

Sometimes, instead of crashing, plates pull apart. This is called rifting. As the Earth's crust stretches and thins, hot material from the mantle rises closer to the surface. This heat makes the land expand and lift, creating mountains.

• Iceland is an island nation that sits on the Mid-Atlantic Ridge, where plates are pulling apart.
• The East African Rift is another area where the land is stretching and lifting, forming mountains and valleys.

Images for kids

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  This picture shows two continental plates colliding to form a mountain range. The Himalayas formed this way.

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  This diagram shows a Foreland Basin System, which can form next to mountain ranges.

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  An example of how rocks can be pushed and folded in layers during mountain building. This is from the Sevier Orogeny in Montana.

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  The Sierra Nevada Mountains in California, as seen from space. These mountains are a result of delamination.

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  Mount Rundle in Banff, Alberta, Canada.

See also

In Spanish: Orogénesis para niños