Volume 7 No. 3 – September 1, 1934
All material courtesy of the National Park Service.These publications can also be found at http://npshistory.com/
Nature Notes is produced by the National Park Service. © 1934
A Story of Mount Mazama
By Warren D. Smith, Ranger-Naturalist
John Wesley Hillman discovered Crater Lake in 1853, but it remained for the late J. S. Diller and Major C. E. Dutton of the United States Geological Survey to discover Mt. Mazama. These two men by their laborious and careful work toward the latter part of the past century reconstructed this pre-historic mountain so faithfully that with only minor additional observations we are able to place before even the most casual visitor a most real picture of this old monarch of the Cascades.
Looking to the north and south from our vantage point we see the broad platform of the Cascades on which Mt. Mazama, Shasta, Three Sisters, Jefferson, and Hood rise as superstructures. All of these mountains, with the exception of Mazama, are relatively intact and except for some ice, water, and wind erosion effects they maintain some semblance of their former outlines. Not so Mazama. Its whole upper portion is missing. To reconstruct its former condition, we must note first of all that its history of building was one dominantly of explosive activity which would of necessity produce a conical shaped mountain and not a low lava dome. Second, its backslopes, which one can see at many points on the Rim Drive, indicate how the curve of these slopes would go if projected upward, and last, the size of its base, which can be measured, will give one a clue as to its magnitude in comparison with other Cascade mountains. By putting together all the observations of the inner and outer parts of the present crater one can bring out the main steps in the history of this old mountain. In doing this we should call attention to the:
- Materials – composition, distribution, texture.
- Profiles – That is, the importance of geological line or pattern which may have entirely different meanings from those the artist sees.
- The factor of time; not actual but the relative ages of materials and happenings.
It is very likely that Mt. Mazama started out very much as Wizard Island did, i.e. as most volcanoes do, as a small cone on this Cascade plateau that grew larger and larger literally by “fits and starts”. There would be a time of quiet upwelling and outpouring of lava to be followed by great paroxysms of violent explosions. This is not a matter of conjecture, for the crater walls carry the inescapable record. There are periods, too, of quiescence when the slopes of the mountain at different stages were forest covered and long erosion intervals occurred.
Geologists and others, who came long after Diller and Dutton, have dug into the crater walls and found beneath sixty feet of debris portions of old charred stumps and logs. The long erosion intervals when valleys were cut in the old lava slopes are proved in many places by the unconformities where valley profiles cut across lava flows and beds of fragmental materials. One such unconformity is remarkably well exhibited in Red Cloud Cliffs where a V-shaped valley was cut by stream action and not ice in the nearly horizontal (as seen in section) lava flows and later filled by a solid flow of lava.
There were also other events of importance in the life history of the old volcano quite different from its episode of igneous (fire-born) action, such as the accumulation of great snow fields on the highest slopes and streams of ice fed by these fields of nevé coursing far down the lower slopes. The records of these are found on all sides of the present crater, both inside and outside the present rim. These records are of three kinds: U-shaped valleys, like Kerr and Sun Notches; glacial scratches like those at Discovery Point, on the north rim between Watchman and Llao Rock and on the Watchman itself; and moraines, at many points on the rim, especially at the heads of Munson and Castle Creeks. Records of at least two and perhaps three separate periods of glaciation may be noted in the study of the crater and its back slopes. In this connection it may be pointed out that it is not at all improbable that some glaciation occurred after the destruction of the main mountain and that this catastrophe took place in the last inter-glacial epoch which, if true, would enable us to date this cataclysmic event to about 15,000 – 20,000 years ago.
In trying to get some conception of the height and shape of old Mount Mazama, we are aided by the knowledge that mountains of the explosive type (which is the rule on the Pacific rim) the slopes follow approximately the sine curve. Bearing all these facts in mind Diller restored old Mazama to a height of approximately 15000 ft. in elevation. With a height of 15000 feet and a circumference of 27 miles at the present rim elevation of 7000 feet we would have a volcano here in former times comparable to Mt. Shasta today.
Having built our old mountain up to its full height we are now ready to decipher the next chapter in its history which was one of destruction rather than that of construction. That something of tremendous consequences and involving forces of unbelievable magnitude were at work here is evident even to those least versed in geological force. But just exactly what and how it happened is not so easy to decide. We know that a mountain mass of approximately 15 cubic miles above the present rim towered up into the blue, also that the present crater contained another mass of material altogether totally some 17 cu. miles of rock and now all this is gone. Here comes the rub, for many competent geologists do not agree as to just what did transpire, like doctors who often disagree as to just of what ails a patient. If doctors disagree, it may be “just too bad” for the sick one, but in this case the patient was old Mazama, and apparently the old fellow is quite dead, and therefore it hardly seems a vital matter to decide how it happened. Why worry our heads about theories? Why destroy the mystery? Let old Mazama rest in peace with its present beauty, and let us be content to enjoy the great spectacle.
This would be all right with most people, but geologists are curious people, perhaps overly curious, who are not satisfied with sheer beauty – they want to know and some day they will solve the mystery of the “Old Man of the Mountain”.
Now among several possible theories, we have two outstanding:
One, the theory of collapse and engulfment; the other that of explosion. Space does not permit us now to discuss the quite antagonistic points of view and furthermore the discussion would involve so much that is technical that readers of this number of Nature Notes would perhaps become weary. Suffice it to say that the trend of opinion among many geologists, among these several foreigners of note, appears to be in the directions of a modification of the older notions; that is to day, toward the theory of explosion. Several knotty points will have to be cleared up, however, before some students of the subject will be satisfied.
With due regard for the fine work in the early days by Diller and Dutton the present writer feels bound to disagree with the final interpretation of this important chapter of the geological story. On several grounds is he led to the conclusion that explosion was the dominant factor in wrecking the old mountain. In the first place, explosion and not collapse is the rule in the wrecking of volcanoes of this type, especially on the Pacific rim. Second, the amount of fragmental material scattered far and wide with Crater Lake as a center. Recent road cuts have revealed the fact that there is a veneer of pumice and “finer ejecta” that conceals much coarser fragmenta on the apparently clean back slopes of the old mountain. Third, the crater itself is a typical explosive orifice and is like that of Kilauea only in the most superficial respects. And finally, since the dominant forces in the earth are working outward, at least in connection with vulcanism, on purely mechanical grounds collapse of a great mass when so much material has been previously extruded violently does not seem to be reasonable.
After the formation of the Crater, by whatever process, the volcanic energy was not altogether spent, since three new baby ones were built up within the wreck of the old one. And no like a giant of old, with the geological vultures of erosion gnawing at its vitals, it lies, enchained. What if some day it lifts its new head of Wizard Island higher and roars again its defiance!