Last September, scientists around the world were puzzled by an unusual rumbling traveling through the Earth. It was a strong signal, but it wasn't an earthquake. No one knew what it was. Now, a year later, scientists have solved the mystery.
Most news on NewsForKids.net is appropriate for all ages. When there is news that may not be suitable for all ages, we try to tag it. You can use the setting below to control whether content tagged in this manner is shown.