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%Bl i f e , : |craters. Highly jittered picture by Frashers, Inc.

We Went to

Mono (Ztatet*

fiot Olrtidian

There are many places in the desert Southwestwhere obsidian may be found, but the location de-scribed by Mora Brown in this month's field trip forDesert Magazine readers is probably the daddy ofthem all. Mono craters not only offer a fine assort-ment of volcanic glass for the rock collector, butthey provide an excellent opportunity to study theformation of this mineral at its source. Here is thestory of one of the most interesting geological areasin California.

By MORA M. BROWN

jT I FEW hundred years ago—which,f / geologically speaking is only yes-

terday—Nature staged a wildjamboree in what is now the Mono basinof east central California.

From deep beneath the crust of theearth steam and gas and molten rock werebelching forth from at least 20 majorvents and numberless smaller ones. Ifaborigines were roaming the desert inthose days it must have been a terrifyingexperience to come upon this scene ofviolence.

But today those craters are silent. Theirlong pipes, driven deep in the earth, areclogged with obsidian. But in the soft

14

grey landscape which they dominate inspite of the nearness of the high Sierras,they seem to wait only the opportunity toblast forth again on another wild rampageof eruption.

I confess to my shame that until lastSeptember, I knew nothing about theMono craters. Husband and I were plan-ning a vacation trip for Inyo-Mono recre-ational area. Mrs. Ray Gabbert of River-side, knowing we were a couple of rock-hounds, told us about the tons of obsidianto be found in the easily accessible craternearest Mono lake. She told us we wouldfind the whole group of craters worthy ofinspection.

Our car loaded with sleeping bags, tent,water containers and supplies for anyplace or weather, we went in search ofrocks and scenery with no fixed goal inmind. From Riverside we took Highway395 over Cajon grade, past the tungstenmine at Atolia, and up into Owens val-ley. Up there it was cold. Snow was fallingon the peaks.

We stopped at Independence for a visitwith the Paul Ritch family. Paul is resi-dent engineer for the Metropolitan waterdistrict, and in the early reclamation daysof Idaho, he and my husband worked to-gether.

We spent the three following days in

THE DESERT MAGAZINE

the lovely cabin which the Ritches builtthemselves at Whitney Portal. With Mt.Whitney towering at the head of the can-yon, with overwhelming cliffs around us,with spots of snow and ice and sunshine,it was much more than beautiful.

At Bishop we made the acquaintance ofone of the valley's best known and bestloved citizens—W. A. Chalfant. It was in1885 that his father P. A. Chalfant estab-lished the Bishop Register and made hisson a partner. Since 1887, the son has beenits only editor and publisher. For manymen, that would be a full time job, but inthose years Mr. Chalfant had been activein valley affairs and has found time towrite three authentic histories of his cor-ner of the world: "Outposts of Civiliza-tion," "Death Valley: The Facts," and"The Story of Inyo." He is now workingon a book about the Mono country.

North of Bishop we climbed Sherwingrade, stopped to see the geyser at CasaDiablo, and came at last to an upgradewhere the big desert valley yielded toevergreens. Soon the ground under theevergreens began to change, until the earthwas replaced by a deep carpet of whatlooked like grey pebbles. But they werenot ordinary pebbles; they were the vol-canic material thrown far and wide whenthe craters were in action.

We reached Deadman's pass. Therethe trees had thinned considerably, andthe grey color possessed everything. Onthe left we saw a symmetrical mound; onthe right were others, one so low it lookedmore like a lake bed. We didn't know it,but we were crossing the southern end ofMono craters.

Soft, pleasing grey. Even the dayseemed to absorb the color, so that, undera bright sun, it had the weird tone we as-sociate with an eclipse. Then the craterslay behind us. But at June Lake Junctionthe highway again swung north, and weparalleled them all their 10-mile length.

Symmetrical and beautiful, bold in thecontrasts made by trees and black obsidianagainst the delicate grey, they are likenothing we had ever seen. "They are likenothing," said Isaac Russell who studiedthem for the U. S. geological survey, "inthe United States or anywhere else to myknowledge."

They made me think of sloping roundsteps set at haphazard levels. The highest

Above—hooking from the obsidianheart of Panum crater toward the la-pelli slopes of the craters to the

south.

Below—Amon Brown examines thecoloring in a piece of Mono craterobsidian. The two huge boulders inthe background are solid masses of

volcanic glass.

D E C E M B E R , 1 9 4 1 15

MOnO CROTER5 FROtTl

• . • - : : ; v . ' To Bridgeport • ' ToUodie

7qJ(oqa Pass

£ / PUMICE ig<m:s

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T3 a •' THE SOUTHERNMOST CRATER :::.y.:w:\

ponum CRfiTC-R. mono LOKC- £ POOHO- is ionD in THE

one occupies center place and wears anobsidian crown. Several cones are toppedwith obsidian. Others are flat and com-posed entirely of the pebbles. In twoplaces the molten obsidian pushedthrough the cinder cone and down theslopes to end in high black cliffs.

From the main highway a number ofdirt roads led toward the craters, but theonly surfaced one is six miles south ofLeevining, opposite the loop road aroundSilver lake. It is marked to Benton, andpasses between the two most northerncones. We followed this road for aboutthree and one-half miles, then took a dirtroad to the crater near the lake. A road ofsorts leads up the slope of the cone but wewould not advise attempting it. Neitherwould we advise turning around in thedeep loose material there.

That crater seems to be the only onewith a name. It is Panum. Really it is twocraters encircled by one steep ring of la-pelli, which is the name given by geolo-gists to the pebbly, porous material whichis thrown out with the first eruption.Lapelli is light in weight, angular, small,and it likes the inside of your shoes.

We climbed through it, sliding back-ward sometimes, to the rim, then down towhere it stopped against a rearing mad-house of angular rock both grey and black.We clawed our way up this and found itto be a vast plug of pure obsidian, upend-ed, fractured, jumbled, and sparkling inthe sun. We had to move with care, andwe wore gloves because the volcanic glasswas sharp.

Both black rock and grey are obsidian.It was the presence of steam bubbles atthe time when the mass was cooling thatdetermined consistency and color.

From the jagged north side we lookeddown on Mono lake, a blue gem in a des-ert setting, dotted with two volcanic is-lands. From the west side we looked uponthe high Sierras, their rugged grey coatsbrightened by the golds and reds ofautumn. Leevining lays between the lakeand mountains, and the Tioga pass roaddisappears between the hills. To the southwas the long chain of craters.

The geological story, as revealed bythe men who understand the formativeprocesses of this earth, is interesting. I ampassing it along to you as it has been toldto me.

Three stages of eruption are represent-ed in Mono craters. The first blast belchedout the lapelli, the fine particles of whichwere carried away by winds, the coarserparticles falling in the neighborhood anddropping in rings around the vents. Inpart of the craters this is the extent of theactivity. They are the flat topped cratersand are composed wholly of lapelli.

In the second phase molten obsidian

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High Sierras, as seen from the "hot rocks'' on Paoha island in Mono lake.Frasher photograph.

bubbles were lengthened by movement.This pumice is found on the surface of theflows. What we found had fallen down.

Such are the rocks of Mono craters.Young rock. The obsidian has a fresh, un-weathered look, and it is plentiful. Andthere it waits in its unique setting for yourexploration, be you rockhound, geologist,or mountaineer.

Should you climb the center crater, thehighest, you would be 2750 feet abovethe lake, 9480 feet above the sea. Vesu-vius volcano rises only 4000 feet abovethe sea, and it is famous. Stromboli rises

was forced through the vent. In somecraters it was forced up to a higher eleva-tion than the ring of lapelli around it. Theinner force, however, was not greatenough to expel it farther, and there ac-tivity ceased. Panum belongs to thisgroup.

The third phase is represented by thetwo overflows which I mentioned before.Here the eruptive force was great enoughto force the hot obsidian over the top,through the encircling cone, and down theslopes. But this hot mass was not likemost of the lava overflow with which weare familiar. Most often the lava is ex-tremely hot, and liquid, and flows rapidlyand far, ending in low humps. But here itwas not extremely hot, only semi-liquid,and it pushed along in a thick sticky mass,cooling so rapidly that it fractured evenas it moved. It stopped abruptly in cliffsfrom 200 to 300 feet high. That is thestory.

From where we stood on Panum we no-ticed that one portion of the crater rangecontained an outcropping of black rock.That rock, we have since learned, is theoldest exposed rock in the group. It isthe remnant of an ancient volcano; it ishornblende andesite, and differs from allthe other outcropping in the range.

Much farther south, and set westwardfrom the craters, we noticed two smallhills. Isaac Russell named them the Aeo-lian buttes. They are composed of pinkrhyolite.

From Panum we took specimens of thevarious types of obsidian, then returned tothe Benton road to see the overflow on theeast side of the craters. Russell calls theseoverflow coulees. I believe I'd call themHell's back yard. A huge jumble of obsid-ian all around us, a high fractured cliff ofobsidian in front of us, pandemoniumcongealed.

Here we could see how pressure, not

Negit Island, also called the "blackisland!' This is the smaller of the twoislands in Mono lake. Paoha island,the larger, is considered the ''young-est" crater in the Mono basin groupand "hot rocks" are still found there.

Frasher photograph.

gravity, had forced its progress, how ithad oozed and folded and fractured as itwent. Angular blocks of it had brokenfree and fallen into the softer mass.Splintered particles of it had hardenedinto conglomerate. There were layers oflapelli in the black, caused by the show-ering of lapelli while the mass still movedand coiled.

We found banded obsidian here. Wehad seen chips of it in Nevada two daysbefore. Now we knew where the huntingPiutes found it. The bands are narrow,semi-transparent, and are formed of layersof microscopic crystals of hornblende,feldspar and biotite. The curves of thesebands, both in small specimens and inhuge rocks, showed the direction of theflow.

Here we found, too, the froth of thevolcano, obsidian which was so filled withminute steam bubbles that it formed pum-ice light enough to float. Indeed, beforethe pumice had completely cooled the

a little more than 3000 feet, and it isfamous. Mono craters average better than9000 feet, and they are scarcely known.Why?

Is it quantity? Is it because there is oneVesuvius, and one Stromboli? Does asingle family of 20 volcanoes dwarf theimagination?

Or is it that tourists, filled with expec-tations of the high Sierras, do not look tothe east? Or, if they do, perhaps they donot appreciate what they see because theyhave been given nothing to expect. Of thisI am sure: If Mono craters were in a placewhere there were no 13,000 foot peaksto dwarf them, they would need onlythemselves to make them famous.

Are they extinct? Could they repeatwhat they have done?

Possibly, say geologists. Their location,and the line they follow, indicate that theywere formed along a fissure, probably abranch of the Sierra Nevada fault. Certain-ly they exist on top of volcanoes of theancient past. If, geologists tell us, therewere great earthquake activity again, if theold fault line should be disturbed enoughto allow the escape of hot undergroundsubstances, they could blast their songagain.

If they should, I'd like to be on hand. . . but not in the front row.

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