Aleutian Arc facts for kids

Map showing the volcanoes and islands of the Aleutian Arc.

The Aleutian Arc is a chain of many active and sleeping volcanoes in Alaska, USA. Imagine a long, curved line of fiery mountains! This amazing arc stretches across the Alaska Peninsula and through the Aleutian Islands. It's a huge part of the Pacific Ring of Fire, a famous area around the Pacific Ocean known for lots of earthquakes and volcanoes. The Aleutian Arc formed because huge pieces of Earth's crust, called tectonic plates, are constantly moving and crashing into each other deep under the ocean. This movement also causes many strong earthquakes in the region.

How the Aleutian Arc Formed

This incredible chain of volcanoes came to be because of a process called subduction. Think of it like this: one giant piece of Earth's crust, the Pacific plate, is slowly sliding *under* another piece, the North American plate. This happens along a deep underwater valley called the Aleutian Trench. As the Pacific plate dives deeper, it melts, and this molten rock, called magma, rises to the surface, creating volcanoes.

The Aleutian Arc started forming about 55 million years ago. It stretches for about 3,000 kilometers (1,860 miles) from the Kamchatka Peninsula all the way to the Gulf of Alaska. In some parts, the volcanoes are on islands in the ocean, and in other parts, they are on the mainland of Alaska.

Diagram showing how one Earth plate slides under another, creating volcanoes.

Deep Ocean Features

South of the Aleutian Islands, you'll find the very deep Aleutian Trench. This trench is like a giant scar on the ocean floor where the Pacific plate begins its dive. Between this trench and the volcanic islands, there's a wide area called a forearc basin, which can be very deep. The Aleutian Ridge is the main structure where the volcanoes sit. It's widest near the Alaska Peninsula and gets narrower as it goes west. The way the plates move changes along the arc, causing different types of activity.

Earthquakes in the Aleutian Arc

The Aleutian Arc is one of the most active earthquake zones in the entire United States! Thousands of earthquakes happen here every year. This is all thanks to the constant movement of the Pacific plate pushing against the North American plate. The Pacific plate moves about 4.8 centimeters (1.9 inches) eastward and 7.8 centimeters (3.1 inches) westward each year.

Image showing the Aleutian Island Arc and the deep trench. The dark blue line shows the trench where plates meet.

Plate Collisions and Shakes

When these massive plates grind past each other, it creates huge amounts of stress. This stress builds up until the rocks break, causing an earthquake. Most earthquakes here happen where the two plates meet deep underground. Some smaller quakes are also caused by the volcanoes themselves as magma moves around.

The Aleutian Arc experiences many strong earthquakes. On average, one very large earthquake (magnitude 8 or higher) happens every 13 years. Smaller but still strong earthquakes (magnitude 6-7) happen about six times a year. This constant shaking shows just how active this part of our planet is!

Volcanoes of the Aleutian Arc

The Aleutian Arc is home to many incredible volcanoes, both active and dormant (sleeping). Here is a list of some of them: