Travel Day Three, Part #3: Crater Lake

Moving on with my road trip up to last month's GSA meeting in Portland, my next stop past Annie Creek was Crater Lake itself. The east and south parts of the rim road were closed, but the exit out the north was open (currently all but the entrance from the south to the Rim Visitor Center are closed). I haven't been on the north exit/entrance to the park for a long time, and the sidetrip off Highway 97 added only a few extra miles (although also a couple extra hours!). The gray photo is from the Crater Lake webcam earlier this morning - normally you can see across the lake from this location.

The first five photos were taken from three stops here, which are all very close together on the West Rim Drive.
This is a fairly standard photo of Crater Lake, with Wizard Island in the west part of the lake, and Llao Rock on the crater rim beyond. Wizard Island, an andesitic cinder cone, formed about 7,200 years ago (Bacon, 2008 and Cranson, 2001/2002).
Llao Rock, the massive cliff on the crater rim behind Wizard Island, is a rhyodacitic dome, with a flow beneath the clouds to the right, that erupted about 200 years before the climactic eruption of Mt. Mazama. The whitish layer beneath Llao rock is an air-fall ash and pumice layer from an eruption just prior to formation of Llao Rock. That explosive eruption about 200 years prior to the climactic eruption produced a widespread ash bed found in northern Washington, southeastern Oregon, and western Nevada, where it was called the Tsoyawata Bed by J. O. Davis before it had been correlated back to its source at Crater Lake (Davis, 1977; Davis, 1978; Bacon, 1983; Davis, 1985).
As usual, the water of Crater Lake was exceptionally blue.
If you make it to Crater Lake when most of the roads are open, be sure to take the boat tour out to Wizard Island (the hike down - and then back up - the crater rim to the Cleetwood Cove boat dock is steep and rocky). After landing at Wizard Island, you can climb the cone to the top, where the trees are fascinating, and where you can also see the cinder cone crater. Then you can get a later boat back to the Cleetwood Trail.
This photo looks across the lake at the west side of Wizard Island, where an andesitic flow reaches toward the west crater wall. The Devil's Backbone can be seen across the flow on the rim beyond, just right of the low mass of trees. This is an andesite dike - the andesite of Devil's Backbone - going up the crater wall (enlarge photo - the upper part of the dike appears to be in shadow). The dike cut through the older rocks about 4,000 to 5,000 years ago (Bacon, 2008).
At stop three (centered here on Google Maps), I looked across the lake toward Cloudcap, which is mostly in the clouds, and I noticed something a ways to the left of it, on the crater wall.
That something can barely be see in this photo, between the trees on the far side of the lake.
Here it is, enlarged a bit, a light-colored line on the opposite crater wall.
It's the Wineglass, after which the Wineglass Tuff was named! Enlarge the photo, and you'll see that the Wineglass is a wineglass-shaped talus slope beneath a layer of Wineglass Tuff (aka Wineglass Welded Tuff of Williams, 1942). Just to the left of the Wineglass is a prominent cliff called The Pallisades, formed by the andesite of Roundtop, which has a K-Ar age of 159±13 ka (Bacon, 2008).
Okay, now I've moved on to stop 4: "Danger Will Robinson!" - and what geologist could resist going beyond this sign? (Another photo of the lake and Wizard Island, ho hum.)
Instead of obeying the sign, I followed my geological instincts to this cliff edge, where I found some great glacial striations and grooves on some lava rock (possibly the andesite of Applegate Peak, which has a K-Ar date of 258±8 ka to the south - Bacon, 2008). The grooves point approximately toward the Wineglass - a northeasterly direction.
Here's an enlargement of the grooves and striations, with a field sandal for scale. It looks to me like the ice was moving to the southwest (lower right in the photo), but I didn't examine the outcrop in detail while there.
The nature of the day was apparent at the Watchman Overlook, where many were standing around waiting for the mist to clear.
The mist came and went, ebbing and flowing, finally clearing for a clear view of Wizard Island. You can see the crater of the cinder cone in this photo, along with an andesitic flow that erupted from vents near the base of the cone. The flow comes almost to the edge of the lake at the Watchman Overlook.
While watching the mist come and go, I took a few photos toward Llao Rock, and just happened to get a bit of the Devil's Backbone in the picture, just beyond the dark foreground mass, in the mist near the water's edge.
Here you can see the lower part of the Devil's Backbone dike, beyond that darkly shadowed mass of rock in the foreground. Beyond that, you can see Llao Rock and the white ash layer below it from a different angle, through the mist. The dark rock in the foreground is part of the andesite of the west wall, which has a K-Ar age of 70±4 ka (Bacon, 2008).
This is the andesitic flow on the west side of Wizard Island, with some deep blue to turquoise water in the shallows around the little islands and in the coves and bays in between them. In case you're wondering what Crater Lake looks like beneath all the water, click here for a great underwater view as seen from The Watchman. You'll see that there is another cinder cone in Crater Lake, one completely under water.
I didn't climb the trail to The Watchman Lookout Station; it looked a little inhospitable to me.

Some References:Bacon, 1983, Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.: Journal of Volcanology and Geothermal Research, v.18, p.57-115.

Bacon, C.R., 2008, Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon, Including the Database for the Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon by David W. Ramsey, Dillon R. Dutton, and Charles R. Bacon: U.S. Geol. Survey Map SIM-2832.

Cranson, K.R., 2001/2002, Cinder Cones in Crater Lake National Park: Nature Notes From Crater Lake v. 32-33.

Davis, J.O., 1977, Quaternary tephrochronology of the Lake Lahontan area, Nevada and California: Univ. Idaho PhD dissertation, 168 p [listed here].

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and California: Nevada Archeological Survey Research Paper 7, 137 p [pdf].

Davis, J.O., 1985, Correlation of late Quaternary tephra layers in a long Pluvial sequence near Summer Lake, Oregon: Quaternary Research, v. 23, p. 38–53.

Williams, Howel, 1942, The geology of Crater Lake National Park, Oregon: Carnegie Institution of Washington Publication 540, 162 p.

Where in the West: Lassen Peak

MJC Rocks of Geotripper correctly identified our mystery mountain as Lassen Peak (sometimes incorrectly called Mt. Lassen). In my first WITW post, I didn't want to say "20th century" eruption because if you Google: 20th century eruption ash nevada - Lassen Peak comes up 2nd and 4th (without the ash it comes up 4th), hence my geologically vague "fairly recent" time descriptor.

Lassen Peak, the southernmost volcano in the Cascade Range, is about 70 km (about 45 miles) northeast of Red Bluff, CA, and about 120 km (about 75 miles) southeast of Mt. Shasta. Lassen Peak's most recent eruptive cycle began in 1914 and lasted until 1921. The largest eruption was on May 22, 1915, with locally devastating pyroclastic flows and lahars, a large ash plume, and ash falling as far east as Elko, Nevada.

The generalized map above, from the USGS - Cascades Volcano Observatory site, shows the volcanic deposits resulting from the eruptions of May, 1915, along with the tree blow-down line, which outlines an area now simply called the Devastated Area. A better version of this map and a more detailed description of events can be found in the USGS Fact Sheet 173-98. You can find other good references and links at the CVO Menu page for Lassen Peak and the Lassen Volcanic National Park website.

Brokeoff Mountain, above, is part of an older, larger stratovolcano sometimes called Mt. Tehama, a volcano similar to today's Mt. Shasta, and almost the same size as Mt. St. Helens before it blew up in May, 1980. Mt. Tehama began erupting 600,000 years ago and continued erupting until about 400,000 years ago, when a collapse caldera formed, similar to today's Crater Lake, without the lake.

On Highway 89, between the south entrance to the park and Lassen Peak itself, you can drive right through the Sulphur Works hydrothermal area, which features hot springs, fumaroles, and bubbling mudpits. Sulphur Works is thought to be part of the central vent area of old Mt. Tehama. In winter, you can cross-country ski up the highway to this area (and elsewhere). For a really great hydrothermal tour, hike down the Bumpass Hell Trail to the Bumpass Hell hydrothermal area. They say that the area is named after a settler who fell into a boiling pool, but people have been wondering about the pronunciation for a long time (bum-pass or bump-ass?).

Above, an example of the volcanic rocks you can see on Highway 89 going north (and switchbacking around a lot) toward Lassen Peak.
Highway 89 is usually open from sometime in June until sometime in October or later. The first time I drove through the park, I was coming south from a family-type get-together in Oregon. We drove over the pass from north to south and stopped at the old ski chalet, which has since been torn down in order to build a real visitor's center. They had some great "Go Climb a Volcano" T-shirts, so we all got one! Currently, you can support the park by going to the online store and buying green wristbands. They also have some great books and posters, inlcuding a poster of the 1915 eruption.

And here's a view of the "backside" of Lassen Peak, from the parking lot in the Devasted Area on the northeast side of the mountain. If you continue driving north on Highway 89, there are other stops to make, one at Subway Cave, an old lava tube - and if you continue on to Mt. Shasta, you can stop at Burney Falls.

UPDATE 18Jun2010: Lutz has a great photo of the Sulphur Works from 2007 at geoberg.de.

UPDATE 22Sept2012: The above photos were taken in October, 2006.

Rock Glacier: History and Links

As part of this ongoing rock glacier series, I thought I'd get into the history of the rock glacier a little bit, as it cannot be found anywhere online in any detail. Most of this information comes from Osborne and Bevis, 2001 (OB2001). I'll have some more photos later, including an aerial view from the peak!

According to OB2001, it was W. Eimbeck who first wrote about the glacier in 1883, with his writing then being reported on by I. C. Russell (1885). Osborn and Bevis go on to assert that W. F. Heald then rediscovered the glacier in 1955 (reported on by Heald, 1956), although Heald said that he didn't rediscover it, he discovered it. His discovery or re-discovery, depending on which account is accurate, was described in Desert Magazine in August, 1956, page 4, as follows:

Interest in [the Wheeler Peak] area as a potential national park developed in recent months after Weldon Heald of Tucson and Albert Marshall of Three Rivers, California, made the ascent of 13,061-foot [13,063] Wheeler Peak and ascertained that a glacier on the east slope of the mountain, first reported by the U. S.Geological Survey in 1883, was still active.... Following his ascent of Wheeler Peak, Weldon Heald wrote: "We arrived at the summit at noon. The view from the wedge-shaped crest of the Peak is utterly magnificent. From our perch on the topmost rocks, 13,061 feet above sea level, we looked out over a 360-degree panorama embracing thousands of square miles of deserts, valleys, hills and mountains in eastern Nevada and western Utah. Then we worked our way down the east slope to the edge of a 2000-foot sheer cliff. There in the depths of a cirque below we saw the ice field described by the Geological Survey in 1888. The surface was broken by what appeared to be a bergshrund, a secondary bergshrund [sic], and below these five parallel crevasses one above another. Every sign indicated that the ice was in motion and this was probably a true glacier."

And this is what Weldon F. Heald had to say about that, in the October issue of Desert Magazine, pages 31-32:

Received my August Desert today and feel you did a mighty fine job of presenting the subject of the proposed park or monument in the Wheeler Peak area—and Norton Allen made a fine map from my rough one. I think this will help the cause along greatly. There's one thing though that seems to be misunderstood. The glacier was not "re-discovered" in 1955, it was discovered. Although Eimbeck saw ice at the head of the cirque in 1883, he neither reported it as an active glacier nor suspected it was one. The reason is rather easy to explain. He did not see into the bottom of the cirque, where the glacier lies, and it is probable he would not have realized that the ice was active because it was covered with too much snow.

The ice Eimbeck saw and reported, and pictured in his engraving, is the neve tongue on the cliffs above the glacier. Many must have seen this upper ice but no one suspected that an active glacier lay in the hidden cirque beneath. We wouldn't have either except that I especially chose September of one of the driest years on record, when all the usual snow had melted away and left the naked ice beneath.

Old-timers tell me that a glacier has been supposed to exist on Wheeler Peak for years. However, it apparently was not this one but an ice field in Wheeler Peak's south cirque. We saw this too, but it is now greatly shrunken and definitely not active. So, inasmuch as no one knew or suspected that a glacier existed in Wheeler Peak's north cirque until 1955, I feel that it was definitely discovered then, and that we discovered it, not Eimbeck. However, it was his tip that made me scout for the ice — but I never had any idea I'd find an active glacier.

Others who wrote about the glacier after 1956 - as cited by OB2001 - include Lawrence (1958), Kramer (1962), Currey (1969), Waite (1974), and Osborn (1990). Some confusion apparently existed as to what to call the glacier and the rock glacier, with the glacier being referred to as follows (again from OB2001):

• 'body of ice...that approaches the condition of a glacier'
• 'glacieret'
• 'ice mass'
• 'active glacier'
• 'ice field'

The rock glacier has been called by the following epithets, according to them:

• 'moraine tongue'
• 'mound of unstable moraine'
• 'rock deposit'
• 'rock glacier'

Various claims have been tossed around as to the active v. inactive status of both the glacier and the rock glacier, with the rock glacier sometimes being referred to as active and the glacier being called inactive to non-existent (the latter notably in an argument against the establishment of a National Monument or Park at Wheeler Peak - as per information from OB2001). It's the glacier that is (or has very recently been) active; it's the rock glacier that's inactive.

That most definitive paper I could find (OB2001) states that the glacier was active at the time of study, and that the rock glacier was not active (the study took place during the 1990's). They state that the "glacier grades into an ice-cored rock glacier downstream" - that would be down hill or down the ice gradient (or water gradient, if the thing is melting). And for various reasons - including topography, shape, vegetation, and presence or lack of certain tephra layers including ash from Mono Craters and Mt. Mazama - they determined that the upper portion of the rock glacier had an origin in the Little Ice Age (sometime from A.D. 1300 to A.D. 1850), and that the lower, lumpy part of the rock glacier had an origin sometime prior to A.D. 1200. Osborn and Bevis (2001) say "...shards of Mono Craters origin incorporated into the matrix of the lower rock glacier indicates a pre-1200 AD origin of that segment." This seems a bit confusing to me, because elsewhere in the paper, when refering to tephra from Mono Craters, they refer to the Mono Craters tephra that is dated at 1200 B.P. (not one from 1200 A.D.). So, I'm not sure what this means exactly, or maybe it has something to do with whether or not the C-14 dates are calibrated. There are numerous tephra layers from Mono Craters, with ages of 560 ± 20, 1200 ± 40, 2060 ± 75, 3730 ± 60, 7270 ± 70, 8235 ± 105, and 9710 ± 80 B.P. (dates from this site; calibrated or not?).

Because the Mazama ash doesn't occur anywhere in the southern Snake Range, according to Osborn and Bevis (2001), I presume that its absence in or on the rock glacier can't be used to determine whether the rock glacier is older or younger than the 6845 ± 50 B.P. carbon-14 date on the Mazama ash, or about 7,700 calendar years ago (Bacon, 1983). According to a map showing the distribution of the Mazama ash, by Sarna-Wojcicki, Champion, and Davis (1983) [per OB2001], the southern Snake Range may be right near the edge of the fallout lobe of the Mazama ash. I found two maps online; one is from Sarna-Wojckicki and Davis (1991), [published posthumously by J. O. Davis]; the other one has an undefined origin, but might be from S-W, C, and D (1983). The latter map is more detailed.

The bottom line is: active glacier (unless it has become inactive during the last decade) and inactive, ice-cored rock glacier.

Rock Glacier Definitions:
USGS Glossary of Glacier Terminology
USGS Rock Glaciers
J. Geophysical Research

References:
Bacon, C. R., 1983, Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.: Journal of Volcanology and Geothermal Research, v.18, p.57-115.

Currey, D.R., 1969. Neoglaciation in the mountains of the southwestern United States. Unpublished Ph.D. Thesis, University of Kansas.

Heald, W. F., 1956, An Active Glacier in Nevada: American Alpine Journal, 10 (1), 164-167.

Kramer, F.L., 1962. Rivers of stone. Pacific Discovery 15 (5), 11-15.

Krimmel, R.M., 2002, Glaciers of the western United States, with a section on Glacier retreat in Glacier National Park, Montana by Key, C.H., Fagre, D.B., and Menicke, R.K., Glaciers of the conterminous United States (J-2) in in Williams, R.S., Jr., and Ferrigno, J.G., eds., Satellite image atlas of glaciers of the world: U.S. Geological Survey Professional Paper 1386-J (Glaciers of North America), 405 p., ISBN 0-067-98290-X.

Lawrence, E., 1958. The Wheeler Glacieret of the Wheeler Peak area, White Pine County, Nevada. Unpublished manuscript, Nevada Bureau of Mines, Reno.

Meier, M.F., 1961, Distribution and variations of glaciers in the United States exclusive of Alaska, in General Assembly of Helsinki, 1960: International Association of Scientific Hydrology Publication No. 54, p. 420–429.

Osborn, G., 1990. The Wheeler Peak cirque and glacier/rock glacier. Unpublished report prepared for the Great Basin Natural History Association. University of Calgary Dept. of Geology and Geophysics.

Osborn, G. and Bevis, K., 2001, Glaciation in the Great Basin of the Western United States: : Quaternary Science Reviews 20, 1377-1410.

Russell, I.C., 1885. Geological history of Lake Lahontan, a Quaternary lake of northwestern Nevada. U. S. Geological Survey Monograph 11, 288.

Sarna-Wojcicki, A. M., and Davis, J. O., 1991, Quaternary tephrocrhonology, in Morrison, R. B. (ed.) Quaternary Non-Glacial Geology: Conterminous United States. Geological Society of America, Decade of North American Geology, Vol. K-2, Boulder, Colorado, 93-116.

Sarna-Wojcicki, A. M., Champion, D. E, and Davis, J. O., 1983. Holocene volcanism in the conterminous United States and the role of silicic volcanic ash layers in correlation of latest-Pleistocene and Holocene deposits. In: Wright Jr., H. (Ed.), Late Quaternary Environments of the United States 2. University of Minnesota Press, Mineapolis, pp. 52-77.

Waite, R., 1974. The proposed Great Basin National Park: A geographical interpretation of the southern Snake Range, Nevada. Unpublished Ph.D. Thesis, University of California at Los Angeles Geography Dept.