Sandi Hoover/Nevada Appeal
Every October for the past 14 years during Earth Science Week, hundreds of Northern Nevadans join the University of Nevada, Reno, and Nevada Bureau of Mines and Geology for a free field trip to explore the region and learn about its geological formation.
The all-day trips can include up to 10 stops, and participants drive their own vehicles in a caravan to each location. A road mileage log and directions are provided online so that no one gets lost along the way.
What makes the trips particularly meaningful is the group of geologists who provide information at each location about the geology of the area, as well as the rocks and minerals found there. This year, participants learned about tufa, or calcium carbonate; wonderstone, a type of rhyolite; and celadonite.
All trips include plenty of time for collecting specimens along the way.
Previous years have taken participants to sites where they could collect specimens such as fish fossils, leaf fossils, mollusk fossils, apache tears, crystals and tufa.
This year, the vehicle caravan met in Fallon and went in search of ancient shorelines and volcanoes in the Grimes Point and Lahontan Mountains area. Stops included the following:
Stop 1: On the west side of Sehoo Mountain, to examine beach deposits from the shore of Pleistocene Lake Lahontan and collect tufa-coated Pliocene basalt. Shorelines of Lake Lahontan, expressed as wave-cut terraces or beach deposits, are visible throughout the area.
Stop 2: Eagles House, to examine and collect unaltered and altered Miocene rhyolite. Crystals in the unaltered rhyolite include quartz, biotite, sanidine, and hornblende.
Stop 3: Near Eagles House, to examine and collect Miocene tuff that was silicified and pyritized, then later oxidized to make the rock commonly known as "Nevada wonderstone."
Stop 4: Also near Eagles House, to examine and collect breccia (containing silicified and oxidized fragments of Miocene lacustrine siltstone) and calcite.
Stop 5: At Grimes Point, to examine (but not collect) petroglyphs carved by prehistoric humans along the shore of the receding Lake Lahontan a few thousand years ago.
Stop 6: Near Grimes Point, to examine and collect pebbles of banded, silicified, oxidized Miocene air-fall tuff (wonderstone) that were naturally polished by stream and wave activity along the shores of Lake Lahontan.
Stop 7: At a green hill between Salt Wells Mountain and Rainbow Mountain, to examine andcollect silicified, celadonite-altered Miocene pumice andconglomerate.
Stop 8: On the east side of Rainbow Mountain, to collect celadonite-, calcite-, and quartz-bearing amygdaloidal basalt and dacite.
Stop 9: If time permits, a stop on our way west, out of Fallon, at Soda Lake, probably the youngest volcano within the borders of Nevada. Volcanic bombs at Soda Lake contain crystals of olivine, clinopyroxene, plagioclase, and magnetite.