A conventional volcanic rock contains no argon right after it solidifies .
常见的火山岩在凝固的时候不含有氩元素。
Argon likes to escape out of rocks when they are very hot , in particular when they are melted into volcanic lava , but is otherwise trapped .
当岩石非常热，特别是熔化成火山熔岩的时候，氩很容易从岩石中逸散出来，但会被其他物质捕获。
The physics underlying this procedure is that potassium , which is plentiful in nearly all rocks , is slightly radioactive and decays to argon , a chemically inert element .
