The entrance to Skylight Cave is easily accessed via a sturdy ladder.  photo by Craig Eisenbeis
The entrance to Skylight Cave is easily accessed via a sturdy ladder. photo by Craig Eisenbeis

Skylight Cave is a relatively large and fairly accessible lava tube about 10 miles west of town. I suppose I will get some complaints for publicizing it, but I have confidence that my readers are responsible stewards of the natural wonders that make Sisters Country the wonderful place it is.

Lava tubes form during a volcanic eruption when the outer surface of a lava flow cools and hardens, but the molten rock below the surface remains liquid and flowing. Sometimes, the lava flowing below the surface moves fast enough that the hard shell on top remains intact after the molten lava has drained away. The result is a lava tube.

These interesting geological phenomena are found all over Central Oregon. They do not always have natural outlets that survive the process; so, unless they do, many may not even be discovered. When openings do occur to provide access from the surface, the resulting cavities never fail to draw interest. Some of these are well known, others, not so much.

In the case of Skylight Cave, there are three major openings to the outside world. The largest provides relatively easy access to the chambers below. The other openings provide smaller window-like "skylights" to the interior, giving the cave its name.

The main section of the cave, where the skylights are found, is a classic example of the interior of a lava tube, in that it really looks like a tunnel or subterranean conduit; and it isn't hard to imagine the molten lava flowing down this tube. There is a second arm of this tunnel that is even longer and much more convoluted; it also requires more dexterity to successfully negotiate.

The entrance is easily seen immediately adjacent to a rough dirt access road, so very little exploration is required. The entrance has a Forest Service sign and even a visitors log. Cave explorers are asked to register in order for the Forest Service to monitor the amount of use the area is receiving.

Although I have spent decades in this area, I only recently learned of Skylight Cave, when a friend at the Sisters Athletic Club suggested that it would be a good topic to write about. As a result, I was rather surprised to see from the log that dozens of people had visited the site in just the last couple of weeks. The vast majority were not from Sisters, so I wondered how the cave became known to them.

The entrance, which is immediately behind the sign, is not too deep and has a heavy-duty, semi-permanent steel ladder in place that provides easy access. Once on the cave floor and facing away from the road, the more taxing spelunking challenge is through a low passageway to the right. The path to the skylighted portion of the cave, however, is straight ahead.

The former lava conduit is quite wide, high, and is mostly wide open. However, footing on the surface is quite precarious because of large, rough rocks and darkness. Be sure to bring your own lighting and be extremely cautious. The skylight effect is said to be most impressive in the morning, but we were there in the early afternoon and it was still quite interesting.

Below the skylights, there is quite a bit of rocky debris where it is obvious that portions of the lava tube roof collapsed to create the skylights. The tunnel continues on past the skylights and eventually dead-ends, as the ceiling narrows down to the cave floor.

The cave is closed during the winter because it is home to wintering Townsend's long-eared bats, a sensitive species. Specifically, the closure is in effect from the first of October until the end of April. A warning sign at the entrance explains that "Human entry during winter can cause bats to awaken too often which may cause their death."

The posted information also includes a warning of a "minimum" fine of $300 for violating cave rules. Everyone's care and cooperation is needed, not only to protect this unique feature and ecosystem, but also to ensure that the site will continue to be open to the public.

To reach this interesting feature of Sisters Country, drive seven miles west from Sisters on the McKenzie Highway (242). Turn right at an obvious major intersection of a gravel road. The junction is marked by a badly worn, and hard-to-spot, forest signpost with the road number of 1028. If you stay on the pavement and make a sharp hairpin turn to the right, you have gone too far.

You will pass several side roads on Road 1028, but stay on it for 3.8 miles. Turn right onto Road 260, shortly after a major side-road junction on the left, which is labeled for part of the "Cross District Trail." The 260 road signpost is also difficult to spot but is on the right after you turn.

The farther you drive, the more the road deteriorates. You don't quite need a 4-wheel drive here, but you don't want to take a low-rider in here, either. A high-clearance vehicle would be best. After turning off Road 1028, continue on the narrowing, worsening Road 260 for 0.7 mile, and you will see Road 230 on the right. Keep straight for about another tenth of a mile, and you will arrive at the Forest Service information sign for the cave. The cave is there, on the right.