The grave robbers of Genghis Khan - P.B Kerr

When the ancient Italian volcano Mount Vesuvius erupts right before
their eyes, djinn twins John and Philippa Gaunt know that a brand-new
adventure has found them. Soon, they learn that volcanoes
all over the world are beginning to erupt and are spewing a strange
golden lava. It quickly becomes clear that there is a peculiar
- and perhaps evil - force at work, causing these disasters. If
the twins can't figure out who is responsible, and stop him, an
environmental catastrophe of epic proportions will devastate the
planet. Will John, Philippa, and their uncle Nimrod be able to use
their powers to save the day once again?