One minute, my high-tech GPS watch showed I was riding along at 23 mph. The next minute, it showed 4 mph.

Such is the nature of the 20-mile trail that circles the Newberry Crater rim.

Sure, there are plenty of flat spots along the way, but slow, grueling climbs and fast, hair-raising descents are a significant part of this challenging Central Oregon mountain bike loop.

The ride offers majestic views of the ancient Newberry caldera, 17 square miles and 1,000 feet deep in most places. Sitting in the caldera are trout-filled Paulina and East lakes and a number of lava beds.

Newberry is one of the most intriguing volcanic areas in the region, so touring the area on a mountain bike allows for a personal perspective vastly different from simply driving a car to the top of Paulina Peak.

To get to the Newberry Crater Rim Loop Trail, first you must access the trail near the summit of 7,987-foot Paulina Peak. Shuttling with two vehicles is one option: leaving one at the bottom, then driving the other to the top.

But I decided to ride my bike up the 1,700-foot climb to the top of Paulina Peak — a sheer, rocky outcropping that towers over Newberry caldera.

This initial climb makes up the bulk of the 2,500 feet of elevation gain throughout the ride, but it is certainly not the end of the climbing.

The 2½-mile ride up the gravel road required about 30 minutes to reach the singletrack near the summit. The loop, best ridden counterclockwise, ends at Paulina Lake Resort.

The first part of the trail is relatively flat, but the route then climbs eastward along a ridgeline just south of the lakes. Below me was Big Obsidian Flow, a huge mass of gray and black lava rock formed about 1,400 years ago when, according to the U.S. Forest Service, the Paulina Lake ash flow spread from near the south caldera wall to Paulina Lake.

Eventually the riding surface turned from dirt to pumice as I advanced along the trail and began descending the ridge. The loose terrain felt almost like popcorn as my tires dug into the light gravel. Riders should exercise extreme caution on this downhill section through tricky terrain.

According to the Forest Service, about 1,600 years ago, one of the Newberry Volcano’s many eruptions produced the Newberry pumice-fall deposit, which blanketed the east flank of the volcano with the pumice there today.

Turning and braking through the pumice was difficult, but I took my time and made it through to the east end of the loop. That area includes a wide, flat trail where I was able to gain considerable speed through a thick stand of lodgepole pine trees.

But soon thereafter the uphill returned, and I pedaled hard up an extremely steep section east of East Lake. I was forced to dismount and walk in a few spots, but I finally arrived at a wide-open area that offered a sprawling view of the entire Newberry National Volcanic Monument.

East Lake sat hundreds of feet below. Towering above the lake was craggy Paulina Peak, where the ride started. Neighboring Paulina Lake could be seen just off to the west.

From the viewpoint, I continued on to the north side of the loop, which took me on a steady climb through thick, shady forest. On this side of the loop, the trail connects with the Swamp Wells Trail, which leads north all the way to Horse Butte, in southeast Bend. Hardy mountain bikers could ride singletrack all the way from Bend to Newberry Crater, if they really wanted to. But the rim loop by itself is certainly enough for me.

After more than three hours of riding that included significant climbing, I was ready for the 6-mile downhill stretch that would take me back to my car at Paulina Lake Campground. The section was sandy and somewhat treacherous, but I made it through the steep descent and back to Paulina Lake Resort, completing the loop in a little more than 3½ hours.

Trail conditions should improve with some rain and milder temperatures as fall approaches, quelling the dust and sand that has accumulated during the summer. But mountain bikers who want to ride Newberry Rim should plan their trip soon, before the snow begins to fall once again at higher elevations.

— Reporter: 541-383-0318,

mmorical@bendbulletin.com