Everything Photographic: J. T. Boysen and his ... - Yosemite Online

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WE HOPE YOU WILL JOIN US TO HELP VISITORS:Gain a deeper understanding of Yosemite ' s natural,cultural and historic story through our OutdoorClassroom educational experiences;Explore their creativity through free hands-on artisticactivities at the Yosemite Art and Education Center;YOSEMITE,ASSOCIATION'BE PART OFSOMETHINGSPECIALWITH YOURYEAR-END GIFTRestore meadows and trails and enhance the visitorexperience as members of our Volunteer Corps;Become the next generation of stewards by participatingin college internships, Junior Ranger and otherprograms geared to ethnically, culturally and geographicallydiverse populations;Enjoy the Yosemite backcountry in all seasons withthe wilderness reservation and safety program, bearcanister rentals to Keep Bears Wild and the OstranderSki Hut ;Obtain high quality, locally published books, mapsand educational products about Yosemite and the naturalworld at our bookstores and information facilitiesas well as through our website (www .yosemite.org), which offers access to a "Virtual Yosemite . "Beyond the park ' s boundaries, the Association broadensconnections in personal and public libraries bypublishing award-winning books, maps, ItVDs,posters and other materials that we hope will educateand inspire the public to conserve Yosemitefor future generations . At the same time, we hopeto encourage talented scholars, writers, artists andstorytellers to share their passion for the park.As fall emerges in Yosemite National Park, theAssociation's vibrant programs are once again helpingpeople gain an enduring attachment to the park.Without the support of more than 11,000 passionatemembers and active donors the Yosemite Associationcould not build these connections . As the nation ' seconomic climate changes, the strong relationshipswe have with our supporters will ensure that visitorscontinue to connect with Yosemite through our manyprograms . We hope that you will join our fall campaignand stretch your support so we can help a new,broader base of people fall in love with Yosemite .Fach year, the Yosemite Association(relies on your donations to makea difference in Yosemite . P7o it.rants likeour Outdoor Classroom . y :ee-s andYosemite-focused publicat :cns .trea :evital stewardship to protect Yos .e :-: :eNational Park, but they wo y d no : Eepossible without your sups:_ Make acommitment to provide o~ ' rtunitiesfor people to learn about . en_iov andexperience Yosemite National Park andthe Sierra Nevada by con :rtiuting to ourfall campaign . You can^e enclosedenvelope or make a donation online atwww.yosemite .org helpas donations.html . This donation will not renewyour membership, but it will help theAssociation build a deeper connection toYosemite for generations to come . Thanksfor your support!It
BY GREG STOCKINVESTIGATING THEEL CAPITAN ROCK AVALANCHEAt 2 :25 on the morning of March 26, 1872, one ofthe largest earthquakes recorded in Californiahistory struck along the Owens Valley fault nearthe town of Lone Pine just east of the Sierra Nevada. Theearthquake leveled most buildings in Lone Pine and surroundingsettlements, and killed 23 people . Althoughseismographs weren't yet available, the earthquake is estimatedto have been about a magnitude 7 .5 . Shock wavesfrom the tembler radiated out across the Sierra Nevada.On that fateful morning, John Muir was sleeping ina cabin near Black's Hotel on the south side of YosemiteValley, near present-day Swinging Bridge . The earthquakeshook the naturalist out of bed . Realizing whatwas happening, Muir bolted outside, feeling " both gladand frightened " and shouting "A noble earthquake! " Herecalled the experience in his 1912 book The Yosemite:I feared that the sheer fronted Sentinel Rock, toweringabove my cabin, would be shaken down . . . The EagleRock on the south wall, about half a mile up the Valley,gave way and I saw it falling in thousands of the greatboulders I had so long been studying . . . pouring to theValley floor . . . After the ground began to calm I ranacross the meadow to the river to see in what directionit was flowing and was glad to find that down the valleywas still down.The earthquake and rockfall profoundly affected Muir,causing him to view earthquakes as the primary mechanismof rock debris, or talus, formation in YosemiteValley. Noting the huge volumes of talus in YosemiteValley, he went on to write:Judging by its effects, this earthquake was gentle as comparedwith the one that gave rise to the grand talus systemof the Range and did so much for the canon scenery.The rockfall witnessed by Muir originated from anarea above the present location of the Yosemite Chapel,from a point known as Eagle Rock . The rockfall wasabout 47,000 cubic yards in size, enough to cover a footballfield nearly three stories high . The rock itself weighedroughly 108,000 tons, making it one of the larger rockfallsin recorded Yosemite history . However, the debrisfrom the Eagle Rock rockfall actually came to rest upon apre-existing, and much more extensive, boulder deposit.Located just east of the Chapel near Sentinel Bridge,this deposit is the result of what geologists call a rockavalanche, an especially large rockfall or rockslide thatextends far beyond the cliff where it originated. MostYosemite Valley rockfall debris accumulates at the baseof the cliffs, forming a wedge-shaped deposit of talus.Occasionally, however, debris from a rock avalanche willextend out much farther across the valley floor.Geologist Gerald Wieczorek of the U .S . GeologicalSurvey and colleagues have identified at least five rockavalanche deposits in Yosemite Valley. The largest of theseoccurred in Tenaya Canyon, at the site of present-dayMirror Lake . Sometime in the past, a rock formation onthe north wall of the canyon just east of and probablysimilar in size to Washington Column collapsed intoTenaya Canyon . The rock debris piled up against thesouth canyon wall to a depth of over 100 feet . There wasso much rubble that it dammed Tenaya Creek, forminga large lake that once extended over a mile upstream ofthe dam . The lake has since been mostly filled in withsediment carried by Tenaya Creek, but what remainsis known today as Mirror Lake . Other rock avalanchedeposits in the Valley can be seen near Tenaya Bridge andat the walk-in campground below Royal Arches.Of them all, perhaps the most interesting and spectacularis the El Capitan rock avalanche deposit, locatedbeneath the southeast face of its namesake . FrancoisMatthes, a pioneering Yosemite geologist with the U.S.Geological Survey in the early 1900s, described the ElCapitan Meadow deposit in 1930:. . . the most remarkable body of earthquake debris is thatwhich lies in front of El Capitan—not the talus of blocksthat slopes steeply from the cliff to the valley floor, butthe much vaster hummocky mass, partly obscured by agrowth of trees and brush, that sprawls nearly half a mileout into the valley. There can be no doubt that it is theproduct in the main of one colossal avalanche that camedown from the whole height of the cliff face probablythe most spectacular rock avalanche that has fallen in theYosemite Valley since the glacial epoch . . . the quantity ofdebris that fell in this stupendous earthquake avalancheis so great. . . that its removal doubtless altered appreciablythe contour and appearance of El Capitan.In 2006, a new digital topographic map of YosemiteValley was made using a technique called Light Detectionand Ranging (LiDAR) . In this technique, a laser mountedon a small airplane emits pulses of light, and a sensor onYOSEMITE ASSOCIATION, FALL 2008
Page 1 and 2: YosemiteA JOURNAL FOR MEMBERS OF TH
Page 3 and 4: BY STEVE HARRISONEVERYTHING PHOTOGR
Page 5 and 6: proofs at the studio ." If that was
Page 7: IAMAKE A DEEPER CONNECTIONTO YOSEMI
Page 11 and 12: The southeast face of El Capitan, s
Page 13 and 14: BY SHELTON JOHNSONFINDING GEORGEQn
Page 15 and 16: estored completely without the rest
Page 17 and 18: YosemiteOutdoor AdventuresDiscover
Page 19 and 20: ADVENTURESy Snow Suvey #10Saturday
Page 21 and 22: SUPERINTENDENT TOLLEFSON TO LEADYOS
Page 23 and 24: December I8 is the last day to plac
Page 25 and 26: PARK PROFILENIKI STEPHANIE NICHOLAS
Page 27 and 28: Welcome to Wawona Evening Reception
Page 29 and 30: Ostrander Ski Hut Trips : Another B
Page 31 and 32: NEW MEMBERS AND RECENT DONATIONSENR
Page 33 and 34: Contributing Members Jennifer & Ben
Page 35 and 36: George Garbesi, Andrea Goicoechea,

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