Sunday, September 21, 2014

Field Trip to Grand Canyon's Trail of Time with Laura Crossey and Karl Karlstrom

Last week the joint meeting of the Arizona Hydrological Society (AHS) and the American Institute of Professional Geologists (AIPG) was held in Prescott, Arizona. The meeting was held at the Prescott Resort - a fantastic venue with a fabulous view of the Prescott area. On September 21 and 22, I led two different groups on a field trip to Grand Canyon's South Rim and the Trail of Time. The trip on the 21st was co-led by myself, Karl Karlstrom and Laura Crossey. This trip had about 25 participants from all parts of the United States. The trip on September 22 had 10 participants.

All of the photo's below were taken by Laura Crossey and are used with her permission.

View from the Prescott Resort to the northeast. The colorful, exposed rocks in the middle distance belong to the Dells Granite, a 1.4 billion year intrusive rock that is now fractured and beautifully sculpted. In the far distance and barely visible are the San Francisco Peaks near Flagstaff. This is a remnant stratovolcano with a collapsed top that forms the circular ring of peaks. Its former height before collapse may have been over 15,000 ft. St. Matthews Mountain (6,307 ft.) is visible on the left between these two features and is likely composed of volcanic rocks between 15 and 10 million years.

Karl Karlstrom getting the field trip started in front of the Bright Angel Hotel. Karl has done a lot of research in the Grand Canyon, beginning with the Precambrian basement rocks (Vishnu Schist and Zoroaster Granite), the Grand Canyon Supergroup, and recently ideas for how and when the canyon formed.

Karl and I in front of the portal at the Precambrian end of the trail. Here we discussed the origin of the idea for the Trail of Time and its uses in geologic education.

Karl and his team had brought most of the rocks out by boat on two different river trips. The Precambrian crystalline rocks shown here are from the Front Range of the Rockies however. They were easier to access there.

Participants viewing a sample of the oldest rock in the Grand Canyon, the Elves Chasm Gneiss.

James A. pondering what it all means.

Karl explaining the fossilized stromatolites from the Awatubi Member of the Kwagunt Formation.

The Trail of Time includes numerous places with newly installed viewing tubes that help viewers see the geology better. Tubes like these are a cherished tradition at Grand Canyon National Park.

Here I am explaining one of my favorite formations in all of Grand Canyon, the Tapeats Sandstone. It is a coarse-grained sandstone deposited in a near-shore, perhaps beach deposit.

Brass rings are found at every meter to mark one million years of time.

On the Kaibab Limestone at Grandeur Point.
Viewing the Bright Angel Fault that has offset the layers about 150 feet. The trail takes advantage of the fault break through the white cliff of Coconino Sandstone.

Our assistants on the trip, Kayla and Rylleigh from Columbus State University in Georgia.

At the one million year marker, the meters expand to cover on hundred million years, then 10,000 years, then thousands of years, hundreds of years, decades, and finally single years. For the last 140 meters, participants can see how time is relative between geologic time frames and human time frames.

It was a great day at the Grand Canyon! Thanks to all for participating and to the two professional organizations who sponsored us.

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