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.

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.