Scientists have found good evidence that strong earthquakes can cause a nearly immediate increase in the activity of volcanoes nearby.

Andrew Harris at the University of Hawaii monitors volcanic hot spots around the globe. With the aid of satellites, he was watching the volcano Merapi as it erupted on the Indonesian island of Java in May, 2006. During that time, a 6.4 magnitude earthquake occurred off the coast of Java and the eruption rate of Merapi increased. Then Harris noticed a nearby volcano increasing its activity at the same rate.

"And the only thing the two volcanoes seemed to have in common was that they'd have both felt that earthquake."

Scientists have long suspected that earthquakes do cause volcanoes to respond. Harris's work provides strong evidence of this link. More evidence came in 2005 when a magnitude 9.0 earthquake triggered a deadly tsunami in the Indian Ocean. That earthquake later was found to have caused a series of minor earthquakes underneath a volcano in Alaska. Harris says the question now is why some earthquakes affect volcanoes while others don't.

"And if we can understand that, we (can) understand a bit more about how a volcano erupts, why it erupts, what forces it to change."

Our thanks today to NASA: explore, discover, understand. We're Block and Byrd for Earth & Sky.