Hole-in-the-Ground

We traveled to eastern Oregon to explore the impact of volcanism on the landscape. Oregon has the deepest concentrations of lava in the world with depositions over a mile deep in the northeast corner of the state. Hole-in-the-Ground was formed 15,000 years ago when magma came into contact with ground water. Steam driven volcanic explosions created this tuff ring (maar), which is almost a mile in diameter and 500 feet deep. (The image is a panorama; click to open it at full width and scroll.)

Fort Rock

Fort Rock was created when magma rose to the surface and encountered the wet muds of a lake bottom. Powered by steam, molten basalt was blown into the air, creating a fountain of hot lava particles and frothy ash. The blobs of hot lava and ash rained down around the vent, cooled in the lake waters, and formed a saucer-shaped ring (tuff ring) sitting like an island in the lake waters. Native Americans once had to canoe to and from the island. This is hard to imagine in the dryness that is now this region!

The wave-cut terraces on the south side of the Fort Rock tuff ring mark former lake levels of this now-dry lake bed. The age of Fort Rock has been estimated at 50,000 to 100,000 years. At its maximum depth, the lake was 200 feet deep.

A lake 30 x 40 miles in width occupied this basin. The water was as deep as the height of this photo, 183 feet deep, as witnessed by our motor home in the lower right corner.

From inside Fort Rock, looking out, the south rim of the tuff ring was washed away. Southerly winds, which are still predominant in this region, drove waves against the south side of the ring, eroding the soft ash layers, breaching it, and creating a large opening on the south side.

After climbing to the top of Fort Rock, one can see another maar, Fort Rock Cave, in the distance. It is the location of an amazing discovery!

These sandals, found in 1936 in Fort Rock Cave, were covered by ash from the Mt. Mazama (Crater Lake) eruption 7,000 years ago.

Thousands of years ago, Fort Rock Cave was a tuff-ring island, and the cave was formed by water. Wind driven waves eroded softer material from under harder rock to create the cave. It was a similar erosion that can be seen on Fort Rock in the distance. There are over 40 tuff-rings (maars) in this basin.

Derrick Cave

Derrick Cave is the largest lava tube in the area. It is 30 feet high and 50 feet wide at the widest point, and 1/4 mile long. The ceiling has collapsed in two places. From this main entrance, one can see one ceiling collapse in the background.

Barely seen from the entrance, and a short hike soon after entering the cave, a "skylight" illuminates the lava tube. A large section of the roof has fallen in.

Looking up, one wonders how many creatures have accidentally tumbled into this pit during the darkness of the night!

One hundred feet deeper into the cave, another roof collapse appeared. From this point, a spelunker needs light to continue deeper into the lava tube.

The roof of the cave gradually lowered until I reached the end of the lava tube. These "lavasicles" indicate the unimaginable heat of a volcano. Super-heated air was intense enough to melt the hardened rock and cause it to sag like melted butter!

After a half-mile round trip underground, the bright, blue sky signaled the exit to the cave. The dark spot on the rock face in the background indicates another cave entrance, which has an interesting history!

About 50 feet north of the entrance to the larger portion of the Derrick Cave is the opening to a much smaller cave. It is the continuation of the main lava tube. These entrances are possible due to the massive collapse of this part of the system.

A few feet inside the cave reveals a steel-rimmed door. In the 1960s, when the U.S. and Russia were at odds, Derrick Cave was a designated a nuclear fallout shelter. It was supplied with food and water for central Oregonians to escape a nuclear holocaust. (The "skylight" at the rear of the lava tube indicates a collapsed roof.)

The entrance to the survival cave originally had a steel door to protect a cache of supplies to sustain the inhabitants for years. It was removed after being repeatedly destroyed by vandals.

The "living room" of the cave was about 100 feet deep and 20 feet wide at the widest point. The idea of central Oregonians living in these cramped quarters for years, waiting for radioactivity to decrease, was more onerous than facing the threat of nuclear fallout! This was another reason for abandoning the project.

Crack-in-the-Ground

We have driven eight miles on a dirt road from the small town of Christmas Valley, Oregon. Carol puts on her hiking boots for the one-third mile hike to the Crack-in-the-Ground.

The eruptions from the Four Craters Lava Field, seen in the background, were accompanied by a slight sinking of the older rock surface, which created the Crack-in-the-Ground. It is a shallow "graben," or sinking of the earth, a tension fracture in basalt. (A larger graben in southeastern Oregon is a vertical subsidence, or sinking, of one mile of the earth from the upper to lower edge!)

Carol is standing at one of several places where the walls of the crack have slumped, thus bridging the gap and allowing access to the deeper parts of the fissure. A portion of the crack reemerges in the background.

In the opposite direction from the photo above, Roy was able to begin a descent into the deep fissure, which is approximately two miles long and up to 70 feet deep.

It is estimated that the crack has remained open for a thousand years. Open cracks or fissures in the earth's surface are not uncommon; they occur fairly often as the result of earthquakes or volcanic activity, but they usually become filled with rock rubble or lava and disappear in a very short time. A large fissure that stays open for hundreds of years is, therefore, a rare feature.

Winter ice is sometimes preserved during the summer in the deeper, more cavernous places where cold air is trapped. Early homesteaders went there to hold picnics and make ice cream, using ice they found in the caves of the chasm.

To squeeze between the walls at this point required removing my backpack.

There are several places where the crack is more difficult to traverse due to huge boulders that have fallen into the abyss. This passage requires hands and knees to scramble under.

After a hike of three-tenths mile along the crack, we reached a saddle where the fissure had again filled with earth. There was still the semblance of a small, auxiliary crack to Carol’s left, but within 50 feet, the earth opened again!

NOTICE !!

THE FOLLOWING POSTS ARE TWO YEARS OLDER (2006), THAN THE PRECEDING POSTS LISTED ABOVE, (2008). WE ARE RESUMING THE BLOG BECAUSE OF RECENT TRAVEL THAT INVOLVED ENGAGING SCENARIOS ILLUSTRATED BY NUMEROUS PHOTOS. THIS BLOG IS THE BEST WAY TO REACH CURIOUS PARTIES INSTEAD OF SENDING LENGTHY E-MAILS TO INDIVIDUALS WHO MAY NOT BE INTERESTED.