Field Trip Information
Trip 1: City of Rocks National Reserve and Albion Range –
June 22, 2010
Leader:Kevin Pogue, Whitman College
From Twin Falls, we'll drive southeast to the Albion Mountains, a north-trending metamorphic core complex that is host to the Almo pluton, an Oligocene granite that forms the incredible domes and spires of the City of Rocks National Reserve and Castle Rocks State Park. We'll spend the morning in the parks viewing textbook examples of granite landforms and discussing the evolution of this spectacular landscape. After lunch, we'll head north along the range where we'll visit outcrops of Tertiary vitrophyre, Ordovician marble, Archean granite, and Proterozoic quartzite and schist. Weather and snow pack permitting; we'll end the trip by driving above timberline to the 9,265 ft. glacially-carved summit of Mount Harrison that features overturned quartzite beds and an amazing panoramic view that encompasses broad swathes of the Snake River Plain and Basin and Range provinces.
This trip involves moderate hikes of up to two miles. Participants are encouraged to bring sunscreen, a hat, and water. A light jacket may be necessary for the high elevation portion of the trip. Lunch and snacks will be provided.
Trips 2 and 3: Effects of Volcanism and the Bonneville Flood in the central Snake River Plain – June 24 and 25, 2010
Leaders:Kurt Othberg and Dean Garwood, Idaho Geological Survey
The Snake River Plain of south-central Idaho records episodes of explosive Miocene rhyolitic volcanism associated with passage of the North American plate over the Yellowstone hot spot as well as Plio-Pleistocene basalt volcanism. This two-day trip includes stops to observe basaltic and rhyolitic rocks that form the central Snake River Plain, evidence of volcanic events and their effect on landscapes and stream dynamics, and depositional/erosional evidence of the Bonneville Flood.
The first day (Trip #2) will begin at the summit of a large shield volcano just north of Twin Falls where the development of the central Snake River Plain and the course of the Bonneville Flood will be observed and discussed. From there, we will move downstream investigating basalt flows, changes in depositional energy from the Bonneville Flood, lava-dammed lake deposits, pillow deltas, and young mass wasting deposits in the Snake River Canyon.
The second day (Trip #3) will begin at the 212-foot Shoshone Falls to examine exposed rhyolite along with the erosional evidence carved by the Bonneville Flood. The trip will then visit Balanced Rock and paleosols and recent mass wasting in Salmon Falls Creek canyon. We will then travel to the confluence between Salmon Falls Creek and the Snake River where dramatic landform changes have occurred as a result of interactions between volcanism and fluvial processes. The trip will conclude by examining two amphitheater-shaped box canyons that feed into the Snake River.
Both trips involve light to moderate hiking of up to two miles. Participants are encouraged to bring sunscreen, a hat, and water. Lunch and snacks will be provided.
Trip 4: Hagerman Fossil Beds National Monument and Snake River Whitewater – June 26, 2010
Leader:Phil Gensler, Hagerman Fossil Beds NM
Hagerman Fossil Beds National Monument is located along the Snake River about 35 miles west of Twin Falls. The monument was set apart in 1988 and consists of 4,300 acres of Glenns Ferry Formation that preserves the world’s richest known Pliocene-aged fossil deposit. In the Hagerman area, the Glenns Ferry Formation largely represents a deltaic environment of ancient Lake Idaho where the remains of over 100 species of fossil vertebrates have been identified. The monument is perhaps best noted for the Hagerman Horse Quarry from which over 200 individual horses (Equus simplicidens) have been recovered.
This field trip will include stops at the Hagerman Fossil Beds Visitors Center in downtown Hagerman, the monument paleontology lab, and a trip to one of the monument’s fossil localities. Topics covered include the history, geology, and paleontology of this National Park Service unit.
After lunch, we will travel on guided rafts down the Hagerman stretch of the Snake River, a six mile section of amazing scenery, flat water, and whitewater (up to Class III). In addition to abundant wildlife, the river provides great exposures of recent volcanism and hydrovolcanism, Bonneville Flood deposits, and recent mass wasting features.
The morning portion of this trip will include a hike of up to half a mile in an open, exposed region. Participants are encouraged to bring sunscreen, a hat, and water. For the afternoon river trip, participants should also bring Teva or similar sandals and quick drying shorts/swimsuits. Dry bags and life jackets will be provided by the guides. Lunch and snacks will be provided.