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Why does the Earth have lava in the middle? – Nora, 6, Florida

Dear Nora,

I live near a few volcanoes. One of them—Mount St. Helens—is bubbling with molten material that will probably gush out as lava someday.

I asked my friend Johannes Hämmerli about lava. He’s an earth scientist at Washington State University.

He told me Earth is mostly solid.

“The very center of Earth is a solid metal ball,” Hämmerli said. “Outside that ball, there’s a thick shell we think is liquid. And the rest of Earth—if you go through the mantle and crust—is pretty much solid.”

Earth formed when a cloud of dust in space collapsed. The elements inside the cloud squished … » More …

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Recently there was an online news article that mentioned cold magma that was flowing on the land. What is cold magma? – Matt, 7, Illinois

Dear Matt,

When I think about volcanoes, I picture molten magma deep inside the Earth. Or burning hot lava pouring down the side of a mountain. But you’re right that there have been news reports that mention cold lava.

I talked about what that could be with my friend Katie Cooper. She’s a geologist at Washington State University.

She told me the news may be using “cold lava” to describe a lahar. That’s a mix of water and rocky debris that sometimes whooshes down the side of a volcano. It's also called a debris flow or a volcanic mud flow.

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