Sunday, September 13, 2015

Circum-Ambulation of Meteor Crater at the Northern Arizona University 3rd Annual Geology Alumni Reunion

Educational panel in the Meteor Crater Visitor Center
Studying geology at Northern Arizona University was perhaps the single best thing I did to promote my career as a geologic educator. Located close to the San Francisco Volcanic Field, the Grand Canyon, Oak Creek Canyon, Monument Valley, the Petrified Forest and numerous other world class landscapes, one couldn't help but become enamored with the fascinating story of earth history on display everywhere. The professors were just as enthusiastic about the place and the small class sizes were ideal for learning. NAU however, has been slow in developing a bond with its former geology graduates but that is quickly changing. Paul Umhoeffer, Professor of Geology at NAU since 1992 and current Director of the Environmental Program, is welcoming back past graduates by arranging an annual three day event in September with gatherings and field trips. This year is the the 3rd ever event with a field trip to Meteor Crater located east of Flagstaff.

This trip was led by Tenielle Gaither (BS, 2008; MS 2011) now working for the Astrogeology Division at the USGS in Flagstaff.

Twenty five of us walked the entire perimeter of the impact crater on a hot September day. We had alumni attend from as early as 1972 and as recently as June of this year!

Location map for Meteor Crater 40 miles east of Flagstaff (copied from Tenielle Gaither's field trip guide).

 Gene Shoemaker's 1959 geologic map of Meteor Crater (copied from Tenielle Gaither's field trip guide).

I had never walked the entire perimeter of the crater so this was a special treat for me. I did once hike to the bottom of the crater with my friend Drew Barringer and you can read about that trip here.

The impact is known to have occurred around 50,000 years ago, an age based on post impact erosion rates and two more tightly constrained dates using surface exposure dating techniques.

This is Whale Rock on the eastern rim of the crater where our first stop was made. The sheer size of some of the ejecta clasts was astounding. This rock is about 30 feet tall as shown with more of its mass beneath the nearby rubble.

More ejecta on the southeast rim of the crater

Some of the old works left by Danial Barringer as he searched for the elusive iron meteorite in the pit of the crater. Scientists now know that most of the bolide was vaporized upon impact with perhaps only 20% of it existing as small fragments.

It was a surprise for me to see so much Coconino Sandstone lying as ejecta on the south rim of the crater as it is located in place in the bottom of the crater. Since some of the bottom-most matrial is lying on the south rim, Barringer suspected that the impactor collided with the earth from a northern trajectory. Other studies yield evidence for impact from the southeast or south, suggesting that it likley impacted at a high angle.

Eolian sand on the south rim

Close-up view of the tear fault located on the north rim of the crater. Whether this is a preexisting fault or one initiated by the impact is not yet known.

Dr. Paul Umhoeffer at Meteor Crater during the 3rd Annual NAU Geology Alumni Reunion

Close-up of the ejecta blanket on the southwest wall of Meteor Crater. It is intriguing to think how high this material might have been lifted upon impact.

Photo of overturned beds within the Moenkopi Formation on the south rim of the crater. See the following image for descriptions, however the light orange sandstone in the left center is the overturned equivalent of the light orange sandstone at right center.

Essentially the same view as above but with annotations showing the location of overturned beds in the Moenkopi Formation. These beds were thrown backwards out of the crater area upon impact. All deformations exposed in the crater occurred within about 10 seconds.

Wide angle view of Meteor Crater from the south side looking north.

Cross-section through Meteor Crater showing elevations above sea level, upturned edge of crater rim, and thickness of breccia in the floor of the crater (copied from Tenielle Gaither's field trip guide).

This is the largest fragment of the meteorite ever recovered from Meteor Crater and is called the Holsinger meterorite. The original bolide was about 100 feet in diameter.

Scenic view of the crater from the south rim

Beds of Kaibab Limestone are progressively oversteepened from bottom right to upper center (beneath the people standing on Barringer Point, the highest point on the rim of the crater).

More massive ejecta boulders from the west rim of the crater

This bench mark has the word METEOR stamped in it

Awesome summertime clouds over northern Arizona

Same, same

Stephen Lang was our Meteor Crater Enterprises guide along the trip. He is not formally trained as a geologist but his knowledge of the crater and the processes that created is astounding and was a special highlight on the trip for me. A job well done Stephen! We need more local guides like you in Arizona!
My friend and colleague Marvin G. (NAU Geology BS, '79; MS '85) stands in front of one of the historic buildings located on the southwest corner of the crater. Marvin has also been instrumental in making these geology reunions fun and welcoming!

View to the south of the silica pits, where silica was mined

Close-up of a wall in the silica pits exposing two large red clasts from the Moenkopi Formation. Many thanks to the folks at Meteor Crater Enterprises for hosting the 3rd Annual NAU Geology Reunion Field Trip!

Wednesday, September 02, 2015

Scenes from the August 9, 2015 Vermilion Cliffs and Highway 89A Flood Event

On August 10 of this year, a large storm cell dumped significant moisture on the south facing Vermilion Cliffs near the small settlement of Cliff Dwellers. A passing motorist shot this video which shows huge rooster-tail waves running over the highway. A local news report had this to say about the large runoff event.

On August 22 I was  at the site of the flood, preparing for an 8-day river trip in Grand Canyon. I drove to the culvert area for this unnamed wash and shot pictures of the debris that was still present near the roadway.

Flaggers Wesley and Aaron work from 7 PM until 8 AM directing traffic to one lane across the damaged portion of the road (shown).

Bulldozers have been here in the ensuing 12 days since the flood, moving rocks off of the highway. They are quite large for the relatively shallow gradient of the stream here.

The dozers have cleared away much of the debris on this, the upstream side of the culvert. But the infilling inside the culvert is impressive.

Damaged fence post near boulders

Some boulders were too large to move and so they were cracked into smaller pieces

Vermilion Cliffs in the background is where the storm dumped its load. The edge of the cliff is a drainage divide and so here is the extent of the drainage area of the flood.

The downstream side of the culvert beneath US Highway 89A, four miles west of Cliff Dwellers

The main stem of the flooded wash, which is a tributary to Soap Creek Canyon. Later in the day, we ran Soap Creek Rapid and saw a few new boulders in the channel of the Colorado River, but these were from the opposite tributary, Jack Ass Canyon.

The culverts size simply could not handle the water an debris in this event and so the flood water jumped the channel. This is an undisturbed portion of the debris fan.

Another view of the waterway of the flood

Boulders casting an early morning shadow across the mud laden floodplain. It's been a great summer for monsoon rain and floods in the Southwest but perhaps just normal with respect to other seasons. What is different is that people are traveling with video cameras now and so once far away events are recorded and put on the web. On August 7, Diamond Creek flooded in Grand Canyon and you can read a boatman's account of the 10,000 cfs flood here.

Tuesday, August 18, 2015

Petrified Forest National Park Begins Its Own Field Institute

Photo courtesy of Petrified Forest Field Institute
Petrified Forest National Park is initiating its own Field Institute that will allow visitors and patrons of the park to get a more in-depth experience in this iconic landscape. Following the lead of many other nearby parks and monuments, Field Institutes have become a fantastic way for people to interact with the cultural and natural histories by utilizing the experiences of local experts.

I will be teaching a one day course on October 16 called Geology of the Painted Desert - Blue Mesa Area (it is pictured above). We'll be wandering around the Chinle Formation looking for the evidence that these colorful deposits were brought in here by ancient rivers - and we may find evidence for some of the life forms that lived along these rivers. If you are local to northern Arizona, please consider joining me on this fun day in one of the most beautiful parts of this underrated National Park. If my class does not fit your schedule, please consider joining another class on a different date.

Use the link to sign up! and see in October!

Photo by Wayne Ranney

Friday, August 07, 2015

Alaska's Tatshenshini and Alsek Rivers

In July, I participated in a wilderness river trip that began in the Yukon Territory of Canada and then entered British Columbia and Alaska. The trip was run through Colorado River and Trail Expeditions - CRATE - the outfitter I use in the Grand Canyon. To call this a "vacation" would convey a sense of easiness that seemed to elude us. We had great weather as you will see. Yet the specter of bad weather, bears, rain and cold were never far away. The trip was enjoyable nevertheless, dare I say, fantastic.

 I had never before set foot in the Yukon Territory so this was a treat

Note the canyon of the Tatshenshini River below the mountain peaks. These mountains are part of Wrangellia - an exotic terrane formed about 225 Ma. It later drifted in from the Pacific Ocean and attached itself to North America by about 120 Ma.

Here is a map of the various exotic terranes that are now part of North America. Our river trip is shown as the yellow line - the Denali fault separates Wrangellia from other rocks near the trips beginning.

 The put-in at about 2,500 feet in elevation. We would end up at sea level in 136 miles.

 And we are underway downstream with about 5,000 cfs. We would end up on about 130,000 cfs. 

Entering the first canyon with oxidized rocks in the canyon walls

It is a pretty narrow passage here

This is Bear Bite Rapids. The rapids on this trip were Class III only.

Exiting the first canyon at the end of day 1, the rocks ahead are part of the Alexander terrane

Wolf tracks on a beach...

...and bear tracks

Colorful rocks of the Alexander terrane

Entering the second canyon

These are glacial debris deposits which we saw along the river corridor from time to time

Dewey and John cooking up some illegal eggs (Canada restricts egg importation due to Bird Flu concerns.

On our first hike up Sediments Creek

Bear claw marks on an Aspen tree

Looking south along the course of the Tatshenshini River

And back to our camp at the confluence of Sediments Creek and the river

Howard and Chris yuking it up around the fire

This is Dryas, a widespread Arctic plant. There is a glacial stadial (shorter time period) called the Younger Dryas, when planet Earth went from relatively warm glacial conditions back to glacial conditions between about 12,900 and 11,500 years ago. It is believed that the onset of the Younger Dryas occurred over a short 10-12 year period and that it ended over an equally short 40-50 year period.

Leaving Sediments Creek, we were treated to sunny skies

Awesome weather

A relatively fresh wolf trackway

On a hike along Alkie Creek

Patterns in tundra vegetation

Sunny skies and warm temperatures cause the snow to melt and the rivers to rise quickly, cloudy conditions reverse this just as fast. We saw many areas where the side streams had risen and overtopped their banks just days prior to our arrival.

An unnamed peak at nearly 9,000 feet

Alkie Creek from the river

Monkey Wrench Rapid

Tilted sedimentary rocks...

...and folded sedimentary rocks - this area has it all

Howard and Ed enjoying the ride with Gregg

I personally saw only one bear but cumulatively there were four spotted. The salmon were not yet running upstream and so the bears were likely still upslope eating berries.

This is a crop of the previous picture

 Amazing dikes running through the thin bedded limestone

Approaching the Fairweather Range mountain front near Towagh Creek

Lunch stop

This is a sediment rich river basin and the rocks on the river bank  provided wonderful collecting opportunities.

Floating down to the Fairweather Range

Camped near the confluence with the Alsek River at Melt Creek

Ed, John and Gerry, and Howard on a day hike

On Melt Creek

Fireweed at Melt Creek

I watched this eagle go about its business all day, flying across the river for food from the nest

And he had some luck

Late evening light on the Fairweather Range

In camp

A beautiful evening

Last light to the east of Melt Creek

Fairweather Range

It never got very dark at these northern latitudes

The next day was clear as well

This the junction with the Alsek River looking north, where the discharge is tripled
A slight variation color between the two systems. We are on the Alsek River from here on out.

The Noisy Range rises near the junction of the two rivers

Glaciers are found in most of the tributaries down here near the high standing Fairweather Range

Fantastic U-shaped valley

In the glacier in the background you can see the rim around the ice where recent recession has occurred.

The river is quite wide in this reach

Can you see the international boundary between Canada and the US, slashing through the forest in the center of the picture. This is where the trees were cut in 1910 during the survey days.

We gathered firewood each night for our camps

Black bear print in the mud


This is Walker Glacier where we did a layover camp. We had four layover camps in 11 days of rafting.

The following day we rowed the boats into the pro-glacial lake and then hiked up on top of the glacier.

It was obvious that this glacier is receding considerably with many melt water streams and lakes on its surface.

 The ice front at Walker Glacier

Rowing home at the end of the day

Ptygmatic folds in the schist rocks

The next day we said goodbye to the Walker Glacier

This is the Sapphire Glacier

It rained most of this day but by the time we arrived at Alsek Lake, we could see the icebergs

View from the hill above Alsek Lake

Iceberg jam in Alsek Lake

Mike, Debbie, Gerry, John, Les, Chris, and Dewey near Alsek Lake

Lush vegetation of the temperate rain forest

This is the delta of the Alsek River where it spills into Alsek Lake. The scale of things here is astounding. The Novatak Glacier can be seen upstream in the far distance to the north. The line of mountains on the left is called the Brabazon Range and it is being uplifted along the Fairweather fault, a northern extension (sort-of) of the San Andreas fault.

Novatak Glacier through the telephoto lens

On our last morning the Fairweather begins to reveal itself from beneath the cloud cover

Morning light on icebergs

Back on the river after our lake interlude

The Fairweather Range

Bald eagle hunting on the bank of the river

Spectacular last look at the Fairweather Range

At the take-out we must de-rig everything and put it on a cart to the airstrip four miles away

Then this refurbished single Otter takes everything back to Haines Alaska. We were ferried later to Yakutat and then a commercial flight to Juneau.

From the air we could see the mouth of the great Alsek River emptying into the Pacific

On the commercial flight to Juneau, the Tatshenshini River made an appearance (top) as we flew over the Fairweather Range.

The mountains at Glacier Bay National Park. This was a difficult trip in some respects but a fantastic one after it is all said and done.