Updated

For all the talks interpretive guide Nick Racine has given to visitors about this volcano, standing on the crater rim and watching it pump out tons of rock left him nearly speechless.

"Holy cow, it's incredible," he said. "It's hard to describe."

Racine, normally assigned to the Johnston Ridge Observatory on the other side of the volcano, joined a group of rangers, scientists and journalists in a five-hour ascent of 8,363-foot Mount St. Helens on Thursday, one week before the crater rim is scheduled to be opened to climbers for the first time since the mountain began erupting in 2004.

Dust, steam and blue-tinted sulfurous gas rose from the horseshoe-shaped crater left by St. Helens' 1980 eruption, which killed 57 people and blasted more than 1,300 feet off the peak.

Near the center of the crater, the volcano is rebuilding itself, churning out a cubic yard of rock per second — a rate that could see the volcano return to its pre-1980 size in just 100 years.

As the cooled lava reached the top of the bulging dome, it fractured and fell in rock avalanches that sounded like crashing glass.

The region's intact volcanoes — Mount Rainier, Mount Adams, Mount Hood — loomed blue and white above the distant clouds, serving as a reminder of St. Helens' once-impressive profile.

When climbing was reopened in 1987, St. Helens became one of the most popular climbs in the country, attracting about 12,000 people a year. But in September 2004, the volcano reawakened with a near-constant drumbeat of little earthquakes. Tourists flocked to the visitor centers to witness the billowing clouds of ash and steam as the U.S. Forest Service closed trails around the mountain.

Since then, the volcano has settled into a pattern of constantly extruding lava with a low gas content, said Tom Pierson of the U.S. Geological Survey. Dissolved gas in lava is what drives most explosive eruptions, so the chances of an eruption sending rock to the crater rim appear remote.

"It's lost its fizz," Pierson said Thursday before the climb. "It just doesn't contain enough gas that would make climbing dangerous."

Still, the Forest Service is recommending safety to anyone who makes the arduous, but not technical, 5-mile hike to the crater rim beginning July 21.

In addition to basic backcountry necessities such as a compass, map and plenty of water, they recommend that climbers bring an ice ax, sunglasses that seal around the eyes to keep dust out, a dust mask, and a climbing helmet, just in case the volcano sends rocks soaring above the rim.

Permits are required to hike above tree line and cost $22 each. The Forest Service will issue up to 100 permits a day, and reservations can be made on the Internet through the Mount St. Helens Institute.

The entire south side of the mountain is being reopened to climbers, as are trails through the blast zone on the north side. The crater itself remains off-limits.

The most popular climbing route begins on the south side at Climber's Bivouac, elevation 3,800 feet.

An easy trail through firs and huckleberries on an ancient lava flow leads to tree line at Monitor Ridge, at 4,800 feet. That's where the scrambling starts, up broken rocks and pumice, through sparse patches of subalpine grasses and flowers, to 7,000 feet, where the trail soon becomes a thick field of ash — like hiking up a steep, sandy dune.

When climbers reach the narrow rim and look into 1.2-mile-wide crater, the ascent's difficulty is quickly forgotten — especially when they consider that nearly everything they see on the floor 2,000 feet below has built up since 2004.

"Everything in our perspective here is new. It's all been erupted over the last year and a half," Peter Frenzen, a St. Helens specialist with the Forest Service, said as he gazed into the crater. "Everything we're standing on is less than 3,000 years old, so we shouldn't be surprised that this thing can pump out rock."

How it pumps out the rock when the lava is so gas-depleted is a question scientists are still trying to answer. As they do, visitors to the crater rim can witness the mountain's rebirth.