Review by Dan Day, NCGS newsletter editor
John's January 13th presentation "A Geological Travelogue from Colorado to California and Hawaii" included over 50 colorful slides illustrating igneous, metamorphic, and sedimentary features spanning the Precambrian through recent times. From the highly deformed and folded 1.7 billion year old Precambrian schists in the Colorado Rockies, John took his audience through a systematic photo-survey of structural and tectonic styles across the western U.S. Several major thrust faults, one juxtaposing Precambrian granites over Cretaceous shales during the Laramide orogeny, were discussed. Scenes from the Great Sand Dunes Monument and an angular unconformity of Miocene lava flows over tilted and deformed Permian red beds captivated viewers. Another series of slides chronicled Cretaceous shales in Mesa Verde National Park that represent a great interior continental seaway spanning the current Gulf of Mexico to the Arctic Ocean during Mesozoic times.
The Utah Canyonlands provided John with exposures of Jurassic dune sands gently tilted by underlying mobilized salt layers that create subtle anticlines in the overlying strata. Shots from Arches National Park and the Four Corners area included rare Indian petroglyphs over 1000 years old from the remote Great Galley in the Canyonlands. John included a slide of the Wasatch fold-thrust belt near Salt Lake City to illustrate Cambrian limestone and shale deposits overlapping onto the North American continent before turning his attention to the Quaternary shorelines of pluvial Ice Age lakes. Landscapes of the Triassic Chinle and Wingate Formations, and from Bryce Canyon completed the stratigraphic column continuously exposed in the walls of Grand Canyon northward to Zion National Park and Bryce Canyon.
Slides revealing complex cave passages cut in Nevada limestones during the Ice Age, volcanic mud flows and welded tuffs from central Nevada ushered viewers into the Basin and Range province with its numerous Miocene caldera eruptions. A visit to this region would be incomplete without a few shots of isolated lakes fed by waters from the eastern Sierra Nevada Range, and drained only be evaporation. Tufa towers in Searles Lake, hydrothermally-bleached volcanics near Virginia City, and Pliocene Lake sediments exposed at Death Valley's Zabriski Point were followed by scenes of exfoliating granite sheets on the side of Yosemite's Half Dome, glacial polished granite at Donner Summit, and flowing groundwater-fed cascades over volcanic flows at McArthur-Burney Falls. John's tour of the continental U. S. culminated with photos of the Point Mugu wetlands in southern California, and natural oil seeps along the Santa Barbara coast.
The final group of slides featured volcanic formations and wetlands on the Hawaiian Islands. John captured the essence of the island chain with pictures of the on-going Kilauea rift eruption, cinder cones on Mauna Kea, waterfalls plunging off precipitous volcanic cliffs, and a rare clear-day shot on top of Maui's Haleakala Crater. Midway Island was the last stop on the travelogue, ending with rusted World War II anti-aircraft artillery juxtaposed with breeding gooney birds on one of the world's largest nesting colonies.
The NCGS wishes to thank John for opening the New Year with a picturesque and entertaining photo journal of his geologic travels across the western United States. His photographic talent is quite evident in his work, and is well complemented by his ability to convey a geologic message to his audience with his photos. For more information on John's photographic endeavors, call him at 925-424-5063.
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