Tuesday, November 30, 2021

Lava tubes of the American West

Two Tubes, Ape Cave, Washington

The American West is home to about a dozen majestic volcanoes. Most of the time we appreciate their towering summits. But what’s underground can be every bit as spectacular.

The volcanoes don’t erupt that often. Only one — Mount St. Helens — has erupted during my lifetime. But occasionally they erupt in such a way that produces dramatic caves, called lava tubes. One of my projects this year was to explore more of them.

There are dozens of these caves scattered across several states, and likely a few more still waiting to be discovered. While they form the same way, they have distinct personalities.

The caves form only when the volcanoes produce basalt lava flows, which are rare. Mount St. Helens has produced only one of those eruptions in its history — an eruption 2,000 years ago that sent a river of lava down its southern flank, a flow that may have lasted for a year. Its 1980 eruption was much more explosive; lava tubes require a steady flow.

Lava cools from the outside in. If the lava flows fast enough, a crust can form around it while it continues to pour. Basalt is low in silica, so its lava form can keep up enough speed to drain through that crust. Flows that are higher in silica are much slower and they end up cooling into a solid mass. When the lava stops flowing, that outer crust is left behind. Step inside and it’s a bit like standing in a subway tube made of volcanic rock.

One of the West’s most famous lava tubes is at Mount St. Helens. The Ape Cave — named for a local hiking group, not the hairy mammal — is about 2½ miles long, the third longest in North America. I photographed it in 2001 as one of my first projects when I switched to digital photography.

Much of the cave is completely dark. The easiest way to photograph it is to set up the camera for a long exposure and wave a flashlight around, “painting” the walls with light. But even that’s hard to do. The picture is determined by the light that accumulates during the exposure. The challenge is to choreograph a performance with the flashlight that results in even, attractive lighting. Digital cameras allows you to check your work after each attempt, although it would still take 5 or 6 tries to get an image that looked right.

Digital cameras have improved greatly since then. You still have to perform the flashlight dance. And you still don’t know if the shot worked out until afterward. But they’re now capable of significantly higher fidelity with less light. Part of the cave project this year was simply to redo old work with new resolution, but it became more than that. That said, the Ape Cave — the first cave I ever photographed — was actually the last cave that I visited this year.

The Ape Cave was much as I remembered it. You enter the cave about a third of the way into it where the ceiling collapsed, providing a natural entry that has been augmented by a staircase. I remember taking my first photo within minutes of stepping into the cave. There was a small trickle of water pouring over one of the rocks on the floor, forming a tiny waterfall. It was still there.

Farther down the lava tube there was significantly more water than on my last visit. It’s always a little wet in the cave. The rock is somewhat porous. Rainwater seeps through it and drips into the cave. But autumn was unusually wet in the Pacific Northwest this year. The inside of the Ape Cave felt more like a shower and a small creek flowed in part of it.

I thought there was an opportunity to use this ephemeral creek to make a dramatic image and found my composition where the cave made a sharp turn. To make the water stand out, I needed to maximize the contrast. I eventually got the idea to light the creek only with reflected light. That would allow the water to shine brightly, but the ground next to it would be completely black.

Creek in Ape Cave, Washington

To make the image, though, I had to send my good friend and hiking partner, John, up ahead and around the corner to shine his light on the back wall. I had to shout instructions to him, which was difficult with the echo of the cave, but he was a good sport. It took many tries, but we got an image.

In addition to illustrating how the water flows through the cave, I also think the basic shapes in the picture resemble lava pouring from a mountain. I picked this particular section because the cave here was shaped like a mountain peak.

The Meatball, Ape Cave, Washington

We also spent time with a unique cave feature called “The Meatball.” When lava was flowing through the tube, a chunk of rock floated down and got wedged in a narrow passage. Here, it’s forever locked in place.

It was a fine end to a wonderful year of lava tube sessions. Early in the summer, I photographed some of the lava tubes in central Oregon.

Hidden Forest Cave, Oregon

Hidden Forest Cave is short — you could explore it in just a few minutes — but it opens into a natural amphitheater full of tall evergreens. I waited for the sun to break through the clouds, illuminating the mouth of the cave with golden light. Shooting from the inside-out, I used it to frame the stand of trees.

Light Shafts, Skylight Cave, Deschutes National Forest, Oregon

In the Deschutes National Forest is another remarkable cave where shafts of light can reach the floor. The spectacular light in Skylight Cave doesn’t last long — less than an hour a day — but at its peak, as many as three beams form from tiny natural skylights were the ceiling has fallen.

Cave Texture, Skylight Cave, Deschutes National Forest, Oregon

While the cave was gorgeous during that window of time, I also enjoyed its patterns and textures even before the main lightshow began. Early in the day, a little indirect light reached the cave floor. Because it had been filtered so much by the forest above, it photographed blue. I used my flashlight to highlight the textures on the cave ceiling. I thought the combination of the two forms of light made for an interesting image.

(Prints of Kevin Ebi's images are available through LivingWilderness.com. Learn about new work by joining his mailing list.)

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