Saturday, March 29, 2014

Uinta Mountains, South Flank Photos

Ashley Gorge on the south flank of the Uinta Mountains.

Site of a recent landslide on the south flank of the Uinta Mountains. The sediments that were activated in the landslide were deposited by glaciers that scoured these mountains during the last ice age.

View of Whiterocks River valley from Ice Cave Peak on the south flank of the Uinta Mountains. Precambrian through Mesozoic rocks dip here to the south off of the Uinta anticlinorium.

Red colored rocks grading up into gray are the Pennsylvanian Morgan Formation.

View from Ice Cave Peak across Whiterocks River valley. The tan beds capping the ridge above the cliffs is the Mississippian Humbug Formation. The cliffs are composed of the Deseret Limestone and Madison Limestone formations, both Mississippian in age. These Mississippian formations were deposited unconformably on the Proterozoic (Precambrian) Red Pine Shale that has been dated at about 770 million years old. You can read more about this area and other areas of Utah in the "Geologic History of Utah."

Friday, March 21, 2014

The Oldest Living Things -- Bristlecone Pines

On a cloudy day in 1999 a group of students and faculty from BYU hiked up into the bristlecone pine forest on the flanks of Wheeler Peak in Great Basin National Park, Nevada. Bristlecone pines are thought to be among the oldest living things on the Earth with some trees older than 5,000 years. According to Wikipedia, "Even the tree's needles, which grow in bunches of five, can remain on the tree for forty years, which gives the tree's terminal branches the unique appearance of a long bottle brush."

 The day we hiked up into the trees was a cool and cloudy fall day. Even though the sun was not shining, these ancient trees were still spectacular.

 My daughter was one of the students in the class. Here she is next to one of the ancient trees.

The rest of the forest was dressed in its fall colors. Don't pass up the chance to visit Great Basin National Park and see the bristlecone pines along with Lehman Caves and other fun stops in the park.

Looking west toward Great Basin National Park and snow covered Wheeler Peak.

Monday, March 10, 2014

Crater Lake and Mount Saint Helens in 1993

In 1993 a group of faculty and students from BYU traveled to Crater Lake and Mount St. Helens. It was 13 years after the 1980 eruption. We planned to hike into the eruption crater. But first a few shots of Crater Lake. Above a couple of Clark's Nutcrackers wait for us to feed them.

 The lake was so smooth and calm that in some pictures it is hard to tell where the lake ends, like the picture below where the crater rim seems to float out into the middle of the sky.

It looks so beautiful and peaceful that its hard to imagine it was once the site of terrible devastation as Mount Mazama erupted to form the crater.

 The Pinnacles shown above are eroded remnants of old fumaroles that released gases through the ash flow tuff that erupted out of Mount Mazama.

 The day of our hike into the summit of Mount St. Helens was in late August and the night before the hike, it snowed on the mountain. I had no coat to wear, so I purchased this vest to keep me warm on the hike. Here I am standing at a rest stop about halfway up into the crater.

The snow cover and clouds produced a mystical feeling as we marched up the mountain. As we entered the crater, we could hear rocks falling almost continuously off of the walls of the crater.

The view of the mountain from a distance. Our hike took us up into the heart of the eruption crater.

Around the mountain as we drove and toured, we saw the recovery of life on the slopes that had been devastated by the blast of the eruption, knocking down an entire forest of trees and laying them out all in the same direction as the blast passed by.

Near the visitor's center was a car demolished by the blast from the volcano with a few of our group looking on. You can watch a video about the eruption produced by the USGS here. Don Swanson, who is featured in the video, was our guide up the mountain in 1993.

Saturday, March 1, 2014

Microcracks and Macrocracks

Photos of fractures from small microfractures to large macrofractures.

Healed microcracks in a quartz grain in granite from the Wolf River Batholith of Wisconsin. Two sets of prominent microcracks are preserved now as trails of liquid filled bubbles and may give clues to the paleostress history of these rocks. In addition a couple of cracks healed with dark iron oxide can also be seen. The horizontal length of the photo is about 5 mm.

Another quartz grain from the granite of the Wolf River Batholith, but stress concentrations along the grain boundary in this grain have created a swarm of cracks radiating out from the triangular shaped feldspar at the top of the photo into the quartz.

A quartz (top yellow) and feldspar (bottom dark and light stripes) in this photo show the microcracks that form along the grain boundaries. The oval spots on the quartz grain are artifacts of the ion milling process used to produce the microcrack sections.

Microcracks in a sample of granite dyed with a fluorescent dye and then illuminated under UV light. The rock which to the eye appears very strong and solid has an extensive network of microcracks, many of them along grain boundaries.

Thin section of a basalt with lath shaped plagioclase feldspar crystals, dark Fe-Ti oxides, and multicolored lumpy pyroxene. A few cracks can be seen cutting across the feldspars.

Scanning electron microscope photo of an open crack in a basalt from Iceland. The oval spots again were produced by ion milling when the sample was being prepared.

A healed crack network on a slab of limy mudstone from the Green River Formation. I am not sure of the mode of formation for these cracks, but they may be formed in a similar fashion to the septarian cracks that are found in some concretions.

 Three massive ash flow tuffs in central Nevada (look carefully in the bottom center of the photo for the group of people as a scale). The middle tuff unit has well developed columnar jointing and a dark vitrophyre at the base of the flow. The top of this middle flow is also less welded and forms a slope covered with sage brush. The lower ash flow (light yellow tan) just above the group of students does not have columnar jointing but it also grades up into a softer, less welded top that forms a slope just below the black stripe of the overlying vitrophyre.