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The Strange Case of the Mountain-Climbing Lava

Today’s mystery concerns geological formations along the slopes of Mount Rainier in Washington state. Mount Rainier is a volcano, so we aren’t surprised to see hardened lava flows left over from past eruptions. We are surprised to see these flows sticking to high ridges and hilltops, ignoring deep valleys to either side. If molten lava flows like other liquids, we’d expect it to follow the path of least resistance and flow down into valleys. Why didn’t the lava do this? How can we solve the mystery of the mountain-climbing lava?

For decades, the prevailing theory of how these features formed went something like this: Long ago, when the molten lava first poured out of the volcano, those hill tops were the bottoms of low-lying valleys. Over eons, flowing water carved new valleys to the sides of the hardened lava. The hard lava didn’t erode as much as the surrounding rock, eventually giving the landscape the appearance it has today. Think about pouring hot candle wax down a channel in a hill of sand, then blowing away some of the sand after the wax has hardened. Can this explain these mysterious features?

Unfortunately, no. For that theory to work, the lava flows would have to be much older than they are. Dating of the hardened lava reveals that they might even be as young as the most recent ice age.

Can you solve the mystery of the mountain-climbing lava?

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