Q: How many volcanoes are in the Pacific Ring of Fire?

A: A total of 452 volcanoes can be found in the Ring of Fire, including several super-volcanoes that could destroy our entire civilization.

Q: How many volcanoes are in the United States?

A: The U.S. has 169 volcanoes, most of which are in the Ring of Fire.

Q: What is one of the most early warning signals of volcanic activity?

A: A common early warning sign of volcanic activity is shaking -- tremors caused by volcanic activity underground.

Q: Can any single tool predict volcanic eruptions?

A: Currently, there isn't one tool that can predict when a volcano will next erupt, but scientists are working on new strategies to do just that.

Q: What is lava?

A: Above ground, lava is melted rock, but below the surface, it's called magma. The lifeblood of a volcano, magma produces unstable gases, which trigger eruptions.

Q: Where does a volcano collect its magma?

A: Magma collects in a giant magma chamber below the surface. The bigger the magma chamber, the bigger the eruption.

Q: How big can magma chambers get?

A: Some magma chambers cover 1,000 square miles.

Q: At what temperature does rock melt?

A: As temperatures approach 2000 degrees F (1090 degrees C), that's enough for rock to melt.

Q: How many people have been killed by eruptions of Mount Etna?

A: Over the centuries, Mount Etna has killed tens of thousands of people.

Q: What can gas emissions tell us about a volcano?

A: Volcanic gas emissions ramp up during an eruption. Measuring, for example, a key volcanic gas like sulfur dioxide can give clues to an eruption's size.

Q: What instrument was used in the Curiosity episode "Volcano Time Bomb" to measure volcanic gases?

A: Volcanologist Andrew McGonigle used ultraviolet cameras to measure sulfur dioxide on Mount Etna. The camera images were relayed to the control center. When spikes in sulfur dioxide are registered, it means more magma is on the way.

Q: Were volcanologists able to predict a strengthening of Mount Etna's eruptions with the ultraviolet cameras?

A: Yes, when the camera readings taken by volcanologist Andrew McGonigle recorded high levels of sulfur dioxide, Mount Etna's eruptions indeed grew stronger. Scientists learned that measuring gas emissions is an effective tool for determining the size of an eruption. (Thankfully, timely evacuation notices kept both the researchers and the general population safe.)

Q: What disruptions were caused in March 2010 when an Icelandic volcano erupted?

A: A remote Icelandic eruption in March 2010 threw a deadly ash cloud 30,000 feet (9,144 meters) into the air. A jet stream blew the cloud across European airspace. Because the ash could choke jet engines and place untold lives in jeopardy, some 100,000 flights had to be canceled over a six-day period, costing billions.

Q: How can GPS stations monitor volcanic activity?

A: GPS stations can watch a volcano from space. When magma underground rises, it inflates the volcano like a balloon, distorting it from above ground. But there are limits to observing a volcano from space, and no satellite system could have predicted, for example, the March 2010 Iceland volcano eruption.

Q: Can a person travel down inside a volcano to study its processes?

A: A person can if that volcano is considered dormant and its crater has not been sealed by magma. The Curiosity episode "Volcano Time Bomb" explored such a dormant volcano in Iceland that last erupted 4,000 years ago. Molten lava usually cools and seals the entrance to a volcano, but this one instead had a cave 400 feet (122 meters) deep that could be studied.

Q: What discovery did the Curiosity team make in the dormant volcano cave in Iceland?

A: The team gained a key insight into how magma enters a chamber: It seeps into the chamber through soft rock. The surprising find gives scientists a more complete picture of how magma systems work.

Q: When and where did America's deadliest volcanic eruption take place?

A: In May 1980, Mount St. Helens erupted in Washington state, unleashing a superheated hurricane of wind and rock. Every living thing in its path was instantly obliterated.

Q: What is the Spider seismic instrument?

A: The Spider is a tool that combines an array of monitoring devices into one portable and durable package. It was designed to gather data on seismic activity and ground deformation. The Curiosity researchers were able to successfully place the Spider inside Mount St. Helen's treacherous crater, where it was able to begin transmitting data.

Q: Does the U.S. have any super-volcanoes?

A: Yes; in fact, two of the biggest super-volcanoes are in the U.S. There's one in Yellowstone National Park and the other is near eastern California's Mammoth Mountain.

Q: How powerful is the super-volcano in Yellowstone?

A: The active volcano in Yellowstone has the potential for an eruption thousands of times more powerful than the 1980 eruption of Mount St. Helens. An eruption of that size could bury western North America and dim the sun behind a sulfur haze that would send the whole world into volcanic winter.

Q: Can scientists predict super-volcano eruptions long in advance?

A: Not at this time. But there is some hope that measuring radon gas could help. Small amounts of the gas escape from active magma chambers. As radon decays, it forms radioactive isotopes with unique chemical signatures that scientists can measure.

Q: Can radon in the Yellowstone volcano be detected?

A: It's possible, but Yellowstone's unique geology makes it tricky. A magma chamber the size of Rhode Island lies miles below the surface, and a vast reservoir of water sits directly above the chamber. Isolating the radon is not an easy task. Ultimately, the Curiosity team was able to perform its radon tests.

Q: What did the radon testing of Yellowstone's super-volcano conclude?

A: The radon test confirmed that there’s no threat of a super eruption … for now, that is!

Q: What is the reason for high concentrations of carbon dioxide at California's Mammoth Mountain?

A: High concentrations of CO2 found there can only indicate the presence of magma. Mammoth Mountain stands on the edge of an ancient volcano, the Long Valley super-volcano.

Q: When did the Long Valley super-volcano last erupt?

A: It last erupted 760,000 years ago, covering the ground in red-hot ash for thousands of miles. The presence of CO2 there today indicates that the magma chamber is still in the volcano and is as dangerous as ever. If Long Valley were to erupt again, it could change the course of human history.