Hollywood erupts: catch the drama of red-hot lava in two new volcano flicks.

A glowing avalanche of hot volcanic ash cascades down Dante's Peak into the lake below. Huge clouds of steam rise from the water. As volcano scientist Harry Dalton and his friends race across the lake to escape through the forest, they notice hundreds of dead fish floating by. In a flash, their metal boat begins to disintegrate beneath their feet ....

Cut! This scene is from Dante's Peak, a natural-disaster flick that opens this week. It's one of two Hollywood blockbuster films premiering this year starring red-hot, erupting volcanoes. In the other film, Volcano, hot lava incinerates the streets of downtown Los Angeles.

Natural disasters like volcanoes can be tricky "stars" to work with, says Roger Donaldson, a former geologist and director of Dante's Peak. For one thing, volcanoes have steaming-hot tempers. They get their theatrical "inspiration" some 60 kilometers (37 miles) beneath Earth's crust. That's where huge rocky chambers fill up with magma, molten rock as hot as 1,204[degrees]C (2,200[degrees]F). Tons of solid rock pressing down from above make the pressure soar in these magma chambers.

Scientists aren't certain what triggers an eruption. But they do know that gases dissolved in the magma, like carbon dioxide bubbles in a shaken soda bottle, help propel the pressurized ooze through cracks in Earth's crust.

Part of a volcano's inherent drama is that scientists can't always predict when one will blow. And when they do, people don't always believe the threat is real.

That's the plot of Dante's Peak. Pierce Brosnan, playing volcano scientist Harry Dalton, tries to warn residents of the fictional town of Dante's Peak, Washington, that the mountain on which they live is about to bury them in lava and ash.

Like real volcanologists, Dalton and his colleagues take measurements that often signal an impending eruption. First, Dalton checks out the scene at a mountaintop lake formed in a caldera, the crater left by an ancient eruption. He slips a strip of litmus paper into a sample of lake water. The paper comes out dark red -- a sign that the lake water is highly acidic. The acid comes from sulfur dioxide gas, which percolates to Earth's surface with rising magma.

"We make the most of that in our movie," says Donaldson, referring to the gruesome scene in which acid eats away at Dalton's boat.

Next, Dalton notices that trees and squirrels near the lake are dying. They're probably poisoned by pockets of carbon dioxide gas belched up with the magma, he reasons.

If these signs aren't threatening enough, scientists in the town also use seismometers to record rumbling vibrations beneath the mountain. These tremors, caused by rising gases under tremendous pressure, often precede an eruption, Donaldson says.

Finally, using an electronic tiltmeter, Dalton discovers that the mountain is actually bulging! That sometimes happens as magma collects underground and tries to punch its way through surface rock.

Clearly, the writing is on the wall: This mountain is going to blow!

LAVA IN L.A.?

Of course, many volcanoes erupt with little or no warning. In Volcano, a burst of lava erupts from a hidden source beneath downtown Los Angeles, where no volcano even exists. Tommy Lee Jones, playing the director of L.A.'s Office of Emergency Management, tries to head off the lava as it bubbles up through the La Brea Tar Pits, an active geological site that normally oozes gummy oil. Now lava threatens to incinerate Wilshire Boulevard and swallow Beverly Hills.

The movie doesn't give details on the geological events that lead up to the eruption, admits Mick Jackson, Volcano's director. But the action implies that, behind the scenes, pressure is building in a magma chamber under the tar pits. A massive earthquake nearby shakes the area. opening a crack to the surface. The crack provides a channel for the pressurized magma to spew up and flow through subway tunnels.

Real-life earthquakes have set off volcanic eruptions in the past. "In 1896 and 1975, a big earthquake near Mount Kilauea in Hawaii triggered an eruption at the summit," says Rick Hazlett, professor of geology, at Pomona College in California and a science adviser on Volcano.

In fact. if you plotted the locations of earthquakes and volcanoes on Earth, Hazlett says, you'd notice that many of them overlap. Together, they form a "Ring of Fire" that lines the coastal areas of the continents surrounding the Pacific Ocean.

Scientists say the ring's pattern follows the borders of Earth's tectonic plates, giant slabs of crust floating on molten rock. When these plates collide, they often cause earthquakes that leave cracks in Earth's surface. When one plate slips beneath another, as on the California coast, the rock of the lower plate plunges downward into the mantle, or thick layer of Earth between the core and the crust. The rock melts and becomes magma, the stuff from which volcanoes -- and Hollywood blockbusters -- are made.

But could a volcano really erupt in downtown Los Angeles? "It's not something to realistically worry about," says science adviser Hazlett. But, Jackson says, "It's in the realm of possibility. Our knowledge of what lies beneath L.A. is sketchy at best. No one would say this is entirely impossible."

As one character in Volcano points out, volcanoes can pop up where you least expect them. He cites the story of a Mexican farmer who, in 1943, noticed steam rising from his cornfield. Soon a spray of volcanic ash shot up and flowed over the land. By the end of the eruption, nine years later, a new 503-meter (1,650-foot) volcano -- Paricutin -- stood over the area.

Will the characters in Dante's Peak and Volcano witness similar events? Will they get out in time? We wouldn't want to blow the endings! Head to the movies and see for yourself!

To watch volcanoes erupt online, visit this Web site: http://volcano.und.nodak.edu/

To learn more about Dante, a robot that travels into volcanoes, visit this site: http://maas-neotek.arc.nasa.gov/Dante.dante.html

* Mammoth Mountain, a ski resort in California, has threatened to erupt for years. The soil has been oversaturated with carbon dioxide, killing off a cluster of trees. Recently, some cross-country skiers almost passed out from inhaling the gas. Now, part of the mountain has been cordoned off in case of an eruption.

* Before Mount St. Helens' 1980 eruption (left), rising magma bulged to form a 610-meter (2,000-foot) by 152-meter (500-foot) mountainside cliff. After several weeks, the mountain erupted with a blast 500 times more intense than the atomic bomb dropped on Hiroshima, Japan, at the end of World War II.

* In 1973, a volcano in Heimaey, Iceland, suddenly erupted, threatening to cover a port city with burning lava. Island residents sprayed seawater on the lava to cool it down and slow its flow. Many homes still burned, but 5,000 people evacuated safely and their port city survived.

* Popocatepelt, a volcano near Mexico City, has been dropping ash on nearby towns since 1994. Records show that past eruptions started with similar bursts of ash. Some 30 million people live in view of the volcano. Scientists are bracing for a major eruption.

RELATED ARTICLE: Directing scenes on science

Roger Donaldson, 51, director of Dante's Peak, grew up in a small mining town in Australia. He studied geology after high school and later worked for a mining company, searching for minerals. How did he break into filmmaking? "My other passion was photography," Donaldson says. "I drove my parents crazy when I turned the bathroom into darkroom." After working as a photographer for 10 years, Donaldson switched to motion pictures. To prepare for Dante's Peak, he flew over the crater of Washington's Mount St. Helens and interviewed eyewitnesses who watched the mountain blow its top in 1980.

For a free brochure called "Careers in Geosciences," write to:

Geological Society of America 

P.O. Box 9140

Boulder, CO 80301-9140

RELATED ARTICLE: If you see this month's volcano blockbusters, look for scenes based on these REAL-LIFE ERUPTIONS

* In a six-year period, beginning with an eruption in 1983, Hawaii's Mount Kilauea (right) poured out enough lava to pave a highway that could circle Earth four times. The hardened lava added more than 100 new acres of land to the island.

* In 1985, the hot ash of the Nevado del Ruiz volcano in Colombia, South America, melted part of the mountain's ice cap. Water mixed with soil to create huge rivers of mud that inundated the valley below. By the next day, 22,000 people hoc been buried alive; 10,000 more were injured.

* When Mount Pinatubo in the Philippines erupted in 1991 -- after 600 year of dormancy -- it spewed millions of tons of hot ash into the atmosphere and over homes (above, right).