MANOA — Wearing a T-shirt that read, "Don't worry, I'm a geologist," geology professor Frederick Duennebier called over some fourth-grade students from Wilson Elementary School yesterday to take a swing at creating an earthquake.

"Who wants to go next?" he asked, with a warm smile.

The kids lined up to hoist a sledgehammer and whack a spot on the lawn outside the Marine Sciences Building at the University of Hawai'i-Manoa.

Each spot — all labeled as locations in the Pacific Ocean region — was hooked up to a seismometer. Every time the sledgehammer struck the ground, seismic waves were recorded in a seismograph.

"In general, they're gaining an appreciation for how the world works," said Bruce Appelgate, director of the Ocean Technology Group at UH. "It's not about them growing up to be climatologists. It's about them growing up to be a global citizen. That's what it's all about."

About 4,000 students from kindergarten through high school meandered through the campus yesterday, taking part in the ninth annual School of Ocean and Earth Science and Technology Open House.

The event, themed "Ocean Depths to Outer Space," continues today and is free to the public.

The goal is to engage students, teachers and parents in various science fields through interactive demonstrations, displays, presentations and tours of laboratories and facilities on campus.

Students yesterday got to hold moon rocks, witness simulated underwater lava eruptions, dress in the cold-weather gear scientists use in Antarctica, and see what beach sand looks like under a microscope.

"I feel like a scientist," exclaimed one student from Ma'ema'e Elementary School, peering into a microscope.

The big draw yesterday was a simulation of an explosive eruption.

Hundreds of kids, parents and teachers stood around an area blocked off for the demonstration in which liquid nitrogen was contained in a plastic soda bottle, then submerged in a garbage can full of water.

When the liquid nitrogen converted to gas, it pushed against the plastic bottle, which expanded, then exploded, sending a plume of water high into the air.

The crowd, armed with digital and cell phone cameras, cheered.

"We're discussing how volcanos erupt but in a tangible way," said Julia Hammer, an associate professor specializing in volcanology, who helped organize yesterday's popular demonstration. "It's one thing to tell students why volcanoes erupt, but another to actually show it."

Debbie Kojima, a fifth-grade teacher at Waiolani-Judd Nazarene School, said the event enhances the science curriculum she's teaching in her classroom.

This year she's focused on global warming and how it affects the ocean. Her students have even written letters to the president, urging him to do more about the earth's changing climate.

"For me, I hope (my students) ... realize how important science is in life," Kojima said. "This (event) makes that more real."

Wearing safety glasses, Eli Appelgate, 9, grabbed the sledgehammer and headed to the area on the lawn labeled as the Aleutians.

The fourth-grader at Wilson Elementary — who wants to be a professional snowboarder, skateboarder or baseball player — was determined to generate a huge earthquake.

He lifted the hammer as high as he could and dropped it on the metal plate that sent his seismic wave to the seismograph nearby.

"That was a massive earthquake," said Duennebier's son, Fred Jr., who was helping at the demonstration. "I think you blew up the Aleutians!"

Eli forced a smile, then said to himself, "That hurt."

"This makes science fun," said Dawn Mendiola, a 30-year-old mother of two. "They learn it a lot quicker when they can do it. Get them to read about it? It's impossible."

Reach Catherine E. Toth at ctoth@honoluluadvertiser.com.