英語時差：奇怪的熔巖（上）

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. We can solve the mystery of the mountain-climbing lava through investigation. 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.