Pick up the dusty trail on the side of a bumpy gravel road, walk through a sea of sagebrush, and take a moment to recognize how silent, how still it all is. Then, as the trail seems to come to an end, make your descent into Crack-in-the-Ground.

The crack is an ancient volcanic fissure that measures 2 miles long, 15 feet wide and up to 70 feet deep. It is found in a remote stretch of Central Oregon, at the edge of a dark lava field marked by four cratered cinder cones.

It is a subtly dramatic landscape to the eye, but there is nothing subtle about Crack-in-the-Ground. The short, flat trail offers access inside the fissure, where hikers can clamber over and duck under rocks to explore the fascinating site.

Inside it feels like an open-air cave. The temperature is cold (up to 20 degrees colder than the surface), the air is slightly damp, and narrow rock walls require a few tight squeezes as you go. The volcanic rock is formed into strange, beautiful shapes — odd blobs in spots and sharp, sweeping shards in others.

Tension along a fault zone created the fracture, opening up a fissure in a field of lava that originally flowed from nearby Green Mountain, a small shield volcano, some 740,000 years ago.

It is one of several volcanic attractions in Christmas Valley, a far-flung region of Central Oregon, including Fort Rock, Hole-in-the-Ground and the Christmas Valley Sand Dunes. The town of Christmas Valley offers few services, but visitors can get food and gas there.

The Crack-in-the-Ground trailhead is found just north of town on a bumpy gravel road that also leads to a campground and fire lookout tower atop Green Mountain. There is a vault toilet at the parking area, but no other amenities.

A dirt trail leads a short way from the parking area to an entrance into the fissure, with a separate trail that runs parallel above ground and meets up at the end. Taken together, they make a nice loop hike.

While it is an easy walk, Crack-in-the-Ground does have places that require climbing up and down over rocks and piles of boulders.

While you are there, take the time to appreciate this natural wonder. Volcanic fissures typically fill with soil and rock, but this one remains pristine. It gives us a rare look into the mechanisms of nature, and allows us to gaze backward into geologic time.