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mid-ocean ridge

OLogy Series
geology
card
254

mid-ocean ridge

OLogy Series
geology

When viewed from above, the wide-open sea is vast and flat. But venture below and you'll find a varied landscape that includes the deepest valleys and tallest mountains on Earth. These underwater mountains, or mid-ocean ridges, are formed from volcanic activity. They occur where two of the plates that make up the Earth's crust are moving apart. As the plates spread, magma rises up between the cracks and cools and hardens.

How Did Iceland Form?
While most mid-ocean ridges are underwater, small sections might stick up above the water. For example, the island nation of Iceland is a part of the Mid-Atlantic Ridge. The ridge runs underneath the island and as the seafloor spreads, it causes deep faults in the land itself. But another unusual thing is happening beneath Iceland. The island sits over a hot spot, an intensely hot region deep in the Earth's mantle under the crust. Together, the hot spot and mid-ocean ridge release tremendous amounts of heat and lava, causing volcanic eruptions, geysers, and hot springs.

The ocean floor is usually youngest:

near the mid-ocean ridges

near the edges of the oceans

in the deepest waters

Are you right?

Correct!

Mid-ocean ridges are constantly creating new oceanic crust. As the plates slowly move apart, the crust moves towards the edge of the ocean and is eventually subducted or recycled back into the mantle. Oceanic crust is typically much younger than continental crust.

Rosamond Kinzler, Earth scientist

Even though 80 to 90 percent of the world's volcanic activity occurs at mid-ocean ridges, we've explored less than 2 percent. There's still so much to learn about these underwater volcanoes!

One mid-ocean ridge stretches around the globe.

Fact
or
Fiction
?

Fact

The mid-ocean ridge is really the world's longest mountain range. It's more than 70,000 kilometers (43,500 miles) long.

Although sunlight can't reach deep sea environments, the heat produced at mid-ocean ridges supports a community of life.

Fact
or
Fiction
?

Fact

These communities form around deep sea vents, where plumes of hot water and chemicals escape through cracks in the ocean floor. Bacteria is the base of the food web.

Volcanoes are almost constantly erupting along mid-ocean ridges.

Fact
or
Fiction
?

Fact

While they're not explosive eruptions, they do release a steady flow of heat and lava. Most of the world's volcanic activity occurs at mid-ocean ridges.

Definition: a long underwater mountain range formed from volcanic activity
Location: stretches around the globe, through all the oceans
Length: 70,000 kilometers (43,500 miles)
Plate interaction: spreading (two plates moving apart)
Cool fact: In addition to volcanoes, earthquakes and faults are common along mid-ocean ridges.

Image credits: courtesy of AMNH; Rosamond Kinzler: AMNH.