Crater Lake Historic Resource Study

V. Geological and Biological Information on Crater Lake Area (continued)

E. Points of Geological Interest in Crater Lake National Park

Not surprisingly, in or near the park lie reminders of the cataclysmic activity that once engulfed the area, in the form of lava formations on Mazama s sloping sides, extinct volcanic cones, and glacial valleys. Most of the roadways and points of interest are related to these sites. Following are some of the more notable geological features with short descriptions, moving in a generally clockwise direction around the lake:

1. Rim Slopes

Studying the scene from the Lodge on the rim where the automobile-stage has left you, the most vivid impressions of detail are those of the conformation of the inner rim, the cliffs which rise above it, and the small volcano which emerges from the blue waters of the lake.

The marvellous inner slope of the rim is not a continuous cliff, but a highly diversified succession of strata. Examination shows the layers of volcanic conglomerate and lava of which, like layers of brick and stone, the great structure was built. The downward dip of these strata away from the lake is everywhere discernible. . . [17]

The caldera rim at one point is so broken by crags and pinnacles among bristly trees that this spot is called Rugged Crest; its spires were formed by fracturing.

2. Wizard Island

The next most striking object after the gigantic carven cliffs is Wizard Island. This complete volcano in miniature, notwithstanding that it is forest-clothed and rises from water, carries the traveler's mind instantly to the thirteen similar cones which rise within the enormous desert crater of dead Haleakala, in the Hawaii National Park. Wizard Island's crater may easily be seen in the tip of its cone.

Rising 763 feet above the water, this island is an excellent example of the smallest type of volcanic cone. It was formed by globs of cinders, ash, and molten rock shot from the caldera floor, which, because, of their weight, fell back immediately around the vent, producing its steep sides. The lower part of the island is an extremely rough lava field, thinly forested, with eight species of conifers, while the upper two-thirds is composed of cinders, ash, and broken pumice loosely piled on the slopes.

The summit of this perfect little cone is a crater about 90 feet deep and 300 feet in diameter. The cone and its massive flow of black lava in huge blocks form an island about three-fourths of a mile long by one-half mile wide. The low-lying part near the shore encloses a small lake 40 feet deep. The oldest trees on the island date from about 800 years ago, indicating the last volcanic activity of Mount Mazama occurred about 1,000 years in the past. A variety of small mammals, including pika, chipmunks, and golden-mantled ground squirrels, inhabit the island.

Illustration 2. Wizard Island, 1937. Courtesy Oregon Historical Society, Portland.

3. The Watchman

A massive flow of andesite two-fifths of a mile wide and extending one and one-quarter miles downhill. It supports an impressive dike on the lake side.

4. Hillman Peak

The highest point on the rim, at 8,156 feet elevation, Hillman Peak was formed as a parasitic cone when a vent opened on the side of Mount Mazama. The collapse of the parent peak cut Hillman in half, exposing its inner structure. Its spires are ancient feeder tubes for the lava that built the cone and were decomposed and tinted yellowish-orange by the gases and other hot liquids that rose through them.

5. Devils Backbone

This is a vertical wall of dark andesite lining the cliff face and measuring about 1,000 feet long by 50 feet across near the top. A dike formed by molten lava that squeezed into cracks and then solidified, it has been left standing by the erosion of the surrounding material.

6. Llao Rock

This great mass of dacite (a sluggish lava) was produced from a vent somewhere on the upper slopes of Mazama and hardened after moving only a mile or two. The dacite filled in a former explosion crater. This rock rises nearly 2,000 feet above the water--the highest vertical precipice on the rim- -and was formed by the most massive single flow apparent in the caldera wall, with a maximum thickness of 1,200 feet.

7. Red Cone, Timber Crater

These are excellent examples of extinct cinder cones north of the lake, as is Crater Peak to the south.

8. Pumice Desert

A broad flat in the northern section of the park, this desert was covered with pumice and ash over 200 feet deep in some places by the explosion of Mount Mazama. It has only started to be invaded by scattered lodgepole pines. Due to its scarcity of organic matter, few plants have taken hold to further enrich the soil.

9. Mazama Rock

This is a single huge block of andesite at least sixtyfeet high thought to have fallen from or been blown out of Mount Mazama. Erosion has removed surrounding materials.

10. Palisade Point

These are vertical andesite palisades covered with lichens.

11. Wineglass

This is a slide formation caused by erosion, that, when viewed from the opposite shore, resembles an enormous stemmed glass.

12. Redcloud Cliff

This portion of the rim shows seven distinct layers of glacial material, illustrating the relentless advance and retreat of glaciers on Mazama's slopes.

13. Castle Rock (Pumice Castle)

Below Cloudcap a bright orange and pink formation of pumice and tuff protrudes from the caldera wall composed of layers of pumice laid down in the early days of Mazama and covered by later eruptions. Hot gases have colored them orange and apricot. Exposed during Mazama's final collapse, they have since been eroded by wind and water into a formation called Castle Rock.

14. Mount Scott

This is what remains of a parasitic satellite cone of Mount Mazama that grew near its eastern base, presenting on the east a classic symmetrical volcanic silhouette. The western slope has been eroded by glaciation. It was built up before Mazama's collapse and was probably a secondary vent during Mazama's activity. Mount Scott is the park's highest peak, at 8,926 feet.

15. Kerr Notch

Its U-shaped cross-section denotes the glacier that poured through here and carved out Kerr Valley.

16. The Pinnacles

These towering needle-like formations of rock, or stalagmites, called fossil fumaroles, projecting from the Sand Creek Canyon floor, were formed under sheets of volcanic pumice that preceded Mazama's collapse. As the surface of the hot pumice cooled over the years, steam and gases were released by the hot rocks underneath through vents and tubes that were welded into cement hardness by their passage. These ancient vents now stand alone due to the erosion of the surrounding softer materials.

Illustration 3. The Pinnacles. Courtesy Oregon Historical Society.

17. Phantom Ship

Scanning the blue surface, one's eye is caught by an interesting sail-like rock rising from the waters on the far right close to the foot of Dutton Cliff. This is the Phantom Ship. Seen two miles away in certain lights the illusion is excellent. The masts seem to tilt rakishly and the sails shine in the sun. There are times when the Phantom Ship suddenly disappears, and times again when it as suddenly appears. . . . Hence its name and mysterious repute. [20]

A rugged island rising dramatically 175 feet above the lake surface, the "ship" is formed of molten rock and volcanic ash. The "sails" are remnants of a volcanic dike from a smaller mountain pre-dating Mazama, making this the oldest lava exposed in the caldera.

Illustration 4. Phantom Ship. Courtesy Oregon Historical Society.

18. Sun Notch

This cross-section of a glacially-scarred trough is located on the caldera rim. (Kerr Notch and Munson Valley are also evidence of glaciers that draped Mazama s long slopes, some extending as far as seventeen miles toward the valley.)

19. Godfrey Glen and Colonnades

With the Pinnacles, this area ranks as the most significant feature along park roads other than those along Rim Drive. It is composed of fossil fumaroles marking the site of hot gases that rose through the glowing avalanches that once filled the canyon.

20. Union Peak

Its summit is the neck of an old shield cone antedating Mount Mazama.

21. Llao's Hallway

This 125-foot-deep gorge was cut through pumice material by stream erosion. It is located on Whitehorse Creek, a tributary of Castle Creek and once contained a trail leading through narrow passages to numerous cavelike amphitheaters.