John Hogan
and Oleg Kovin looking at andesitic tuff breccia exposed in right abutment
of Hoover Dam |
Empty
Nevada Outlet Works, or valve house. The six 84-inch needle valves
were removed from both outlet works in the early 1960s and used on other
projects |
Geo
372 students and instructors posing by transformers on the Arizona Powerhouse |
Looking
at downstream face of Hoover Dam, built between 1931-35. It is
726 feet high. |
Looking
at Nevada Outlet Works, where rockbolts were used for the first time
in a non-mining application in 1954 to secure rock slabs bounded by
sheet joints. |
Dr.
Rogers standing next to a seep in the right abutment, leaving calcareous
effervesence salts. Excessive seepage necessitated re-grouting of the
entire foundation between 1938-49. |
Students
and instructors gathering to hear a mini-lecture on landslide dams by
Dr. Rogers in upper Peach Springs Canyon |
Profile
of paleolandslide dam in Upper Peach Springs Canyon. This feature
developed sometime during the Tertiary Epoch |
Diamictite
sequence exposed in the paleolandslide dam testifies to a catastrophic
outbreak flood down Peach Springs Canyon |
Incipient
Toreva block landslide along western wall of Peach Springs Canyon
|
Telephoto
view of the detachment headscarp, which has dropped about 200 feet,
leaving an isolated pinnacle |
Peach Springs
Canyon is structurally controlled by the Hurricane fault. Strata
are down-thrown on the west side |
The Hurricane
fault has dropped the western side of Peach Springs Canyon by as much
as 3000 feet, making for different geology on either side of the valley |
Back rotated
Toreva blocks are a common sight in Peach Springs Canyon. As elsewhere
in the region, these landslides floor in the fissile Bright Angel Shale |
Diamond
Peak is a distinctive feature that is bounded by the Hurricane and Three
Spring faults. It was named by LT Joseph Ives in 1858 when he
traveled this same path to the Colorado River. |
Professors
John Hogan (left) and Dave Rogers on the banks of the Colorado River
at Diamond Creek on Easter Sunday 2005. |
Diabase
dike in the preCambrian granite basement adjacent to Diamond Creek rapids |
Examining
slickensides on an exposed fault in the preCambrian granite, about 1.5
miles north of Diamond Creek |
Cross bedding
in Cambrian age Tapeats Sandstone, the basal member of the Paleozoic
sequence in the Grand Canyon region |
Pegmatite
dikes intruding preCambrian granitic basement along eastern side of
lower Peach Springs Canyon |
The west
side of middle Peach Springs Canyon is comprised of the classic Paleozoic
sequence seen across the Grand Canyon. Here the lower slopes are
mantled by bedrock landslides. |
Students
feeling texture of lineations along shear surfaces developed in the
diamictite in upper Peach Springs Canyon. |
Exploring
one of the larger rooms in Grand Canyon Caverns, off Old Highway 66,
about 12 miles east of Peach Springs. |
Petroglyphs
exposed on the Puerco Pueblo at Petrified Forest National Park |
Petrified
wood exposed along the Blue Mesa Loop Trail at Petrified Forest |
Agate Bridge
is an intact petrified tree trunk lying across a small ravine at Petrified
Forest. Oleg Kovin provides sense of scale. |
Petrified
tree trunk exposed along the Crystal Forest Loop Trail at Petrified
Forest |
San Francisco
Peaks stratovolcano complex, as seen from the Grand falls of the Little
Colorado River. This peak was about 16,000 feet high before it
blew its summit off about 400 ka |
Merriam
Crater is one of about 600 volcanic cones/vents in the San Francisco
Volcanic Field. Lava erupting from this source flowed 7 miles
to a 200 feet deep gorge containing the Little Colorado River, blocking
it. |
The latest
work estimates that the Little Colorado River was blocked by lava flows
between 20 and 40 ka. The river flows around the distal rim of
the flows and spills over the rim of its former canyon |
Looking
upstream at the Grand Falls of the Little ColoradoRiver spilling 200
feet back into its incised gorge |
Dr. Rogers
standing next to columnar joints in the pour-over flows that filled
the Canyon of the Little Colorado River, exposed opposite the foot of
the falls |
Jeff Foster
studied the Grand Falls for his research topic, providing everyone with
their own set of handouts |
Looking
upstream at the falls from the narrows, where the USGS has a gaging
station |
Jeff Foster
gives us an oral presentation on the evolution of the Grand Falls over
a small rise so we could hear him |
The lava
filled up the 200 feet deep gorge, then flowed 15 miles downstream,
due to its low silica content. The River has only removed a fraction
of the blockage. |
View of
the Grand Falls flowing full width on March 29, 2005, looking downstream
at the Narrows |
The rough
Aa surface of the Bonito Lava Flow at Sunset Crater National Monument. |
Devon Rumbaugh
gives us some background on the Humphreys Peak stratovolcano from the
summit of Lenox Crater. |
Amy Boulch
tells us about the eruption of Sunset Crater in 1064-65 AD, spewing
3 cubic kilometers of material over an area of 2100 square kilometers |
We enjoyed
learning about fumaroles and spatter cones on the Lava Flow Trail beneath
Sunset Crater. |
Our intrepid
band of hikers poses on the South Rim before heading down the Bright
Angel Trail to see the Canyon up close and personal. |
Dr. Rogers
waves good-bye at the Bright Angel trail head. The upper 500 feet
of the trail was covered with snow and ice. |
Telephoto
view of our group heading down the Bright Angel Trail. |
Overview
of the upper Bright Angel Trail, which is structurally controlled by
the Bright Angel fault. |
The upper
part of the trail was icey and slippery and more than a few people were
slipping, sliding and falling down. |
Short tunnel
hacked out of the Kaibab Limestone along the Bright Angel Trail. |
Overview
of Three Mile House on the trail, perched atop the Redwall Limestone. |
Jeff
Foster and Stacey Greer at Three Mile House on the Bright Angel Trail,
2000 feet beneath the trail head |
California
Condor who joined our group for picnic lunch at Plateau Point (elevation
3860 ft). |
Condors
were introduced into the Grand Canyon about three years ago. They
look like something out of Jurassic Park. |
Telephoto
view of Granite Rapids, the only rapid that can be easily seen from
the Rim. |
Looking
down the Bright Angel fault trace across the Canyon, from South Rim
to North Rim. |
Looking
down at the trail to Plateau Point from Mather Point, up on the South
Rim. Our lunch spot was 3000 vertical feet below. |
The class
assembles for a mini lecture at Mather Point. |
A nice
view of Horseshoe Mesa from Grandview Point on the South Rim.
Dave Hoffman told tales of past backpacking trips... |
Telephoto
view of a portion of Hance Rapid, at the mouth of Red Canyon.
Hance is one of the most difficult rapids in the Canyon. |
Telephoto
view of Unkar Delta and Unkar Rapids in the preCambrian Dox Sandstone,
taken from Lipan Point. |
Looking
towards the Carbon Butte Landslide that Tom Jerris lectured us on.
Tanner Creek in foreground, where Dave Hoffman crossed the river in
a raft he packed down the trail. |
View
of eastern Grand Canyon from Desert View. Desert Watchtower was
designed by Mary Colter
in 1930 for the Fred Harvey Co. |
We stop
to peer into the incised gorge of the Little Colorado River a few miles
inside the Navajo Reservation. At this spot the chasm is 1,600
feet deep. |
Hiking
along the rim of Meteor Crater looking at samples of shocked quartz
|
Sean O'Donnell
lecturing the class on the historical significance of Meteor Crater,
where the salient features of impact structures were unraveled by Gene
Shoemaker. |
|
