Monday, July 16, 2018

Rafting the Geology of the Canyon of Lodore, Colorado

The Set-Up - Dinosaur National Monument and the Douglass Quarry 'Wall of Bones'


Use this map to orient yourself. The monument is located in northeast Utah and northwest Colorado near Vernal Utah. You can also access this map online here to view at a larger scale.

Dinosaur National Monument was created in 1915 because of an upturned bed of rich, fossil-bearing sandstone discovered by paleontologist Earl Douglass in 1909. The monument was enlarged in 1937 to include two long sections of impressive river canyons along the Green and Yampa rivers. I recently led a group of 24 people on a five-day raft trip through Lodore, Whirlpool and Split Mountain canyons along the Green River. My explorations began at the Quarry Exhibition Hall near Vernal Utah, where this life-size model of a Stegosaur is on display.

Visitors take a shuttle bus from the Visitor Center to the recently renovated Quarry Exhibit Hall. Along the way, exposures of the Morrison Formation are evident and this is the rock unit that holds the fossils here. The Morrison Formation is a fluvial (river) deposit from the Late Jurassic (160 to 145 million years ago) with the bone bed having been dated precisely at 149 Ma.

The upturned bed of sandstone is within this building, housing one of the more unique fossil sites in the world.

The discoverer of the bone bed was very keen that the site could be made into a public display and his wishes came to fruition by the National Park Service.

Here is a small section of the wall which stretches over 100 meters in length and 15 meters in height. Twenty complete skeletons were found, along with nearly 1500 individual bones. In 1909 when the site was first discovered only eight bones at the top of the ridge were exposed. As layers were peeled away downslope, more bones came into view. The site is a mass grave of animals!

Many of the bones belong to the huge Sauropods that dominated Late Jurassic landscapes. The climate was semi-tropical and humid but subject to drought and even wildfires.

Allosaurs are also well-represented at the site. This animal is the state fossil of Utah.

An artists scientific take on how the bone bed came to be. The sediments that contain the fossils are known to be fluvial in origin and the direction of the rivers can also be known using the architecture of the sediment body. Using modern coordinates, the rivers flowed northwest to southeast. Since both complete skeletons and disarticulated bones are found here, geologists suggest that during an extreme drought, the river may have gone dry with animals dying next to the drying waterhole over a period of time. Then a large flood moved the bones a short distance downstream where they piled up on the outside bend of the river in a giant bone jam (similar to a log jam after a flood).

The Big Picture - Harper's Corner Road and the View from the Top

A 26-mile long road takes one from the valley floor to the top of Blue Mountain (actually a plateau). With friends and fellow river runners Howard and Ed in tow, we head up the road to see the canyons and landscapes we will be floating through for the next five days. This view is to the east along a fault-lined valley.

Looking down into the canyon of the Yampa River from the Harper's Corner Road.

On top, we found exposures of the Bishop Conglomerate, a course boulder and cobble deposit that accumulated between 25 and 30 Ma on top of a nearly flat, eroded surface. The conglomerate is extensive in this area but is now only found as remnants on top of plateaus. Note the flat-topped surface in the background - it too has the conglomerate on top. The ancient surface is known as the Gilbert Peak erosion surface and was a region-wide erosion surface before the cutting of the canyons commenced.

I couldn't resist and hollered tot Howard to stop the car! A herd of cows were wallowing lazily next to a restricted watering hole. The present-day drought does not allow them to venture too far away. I could not help but think of our morning visit to the quarry, where a similar scene played out 149 million years ago, only with large reptiles instead of large mammals. It seems, the more things change, the more they stay the same!

The Canyon of Lodore - To the Confluence of the Yampa River

This is northwest Colorado and it is BIG country with very little population. The Gilbert Peak erosion surface is clearly seen in the distance. The valley is called Browns Park and formed about 20 million years ago when the crest of the Uintah anticline collapsed into a graben. The Green River likely followed this down-dropped depression east toward the North Platte River and onto the Great Plains before it attained its present course. This is then, an abandoned river valley.

When the Green River abandoned its easterly course through Browns Park, it instead was directed to the south. At the time of the drainage readjustment, the rocks shown in the distance were buried within the Brown's Park Formation. The river at that time had no idea it was being directed on top of a resistant quartzite rock. But as the river whittled away at the Browns Park Formation, it slowly encountered the buried Uintah Mountain Group rocks. It then carved the Gates of Lodore, the site of our river put-in!

After passing the Gates of Lodore, we entered the Canyon of Lodore. The walls were spectacular!

The Uintah Mountain Group is composed of sandstone, quartzite, and minor conglomerate, all fluvial in origin. Detective work reveals that these ancient rivers delivered their load of debris from north to south, during the break-up of the supercontinent Rodinia. This supercontinent began to fragment about 1,100 Ma. A reconstruction of Rodinia is shown below.


Note the positions of the various continents at this time, with eastern Australia right next to western North America, known as Laurentia for this time period. The Uintah Mountain Group was deposited just above and to the left of the letter "L" in Laurentia. (1.1 Ga means 1.1 Giga-annum or 1.1 billion years ago; belts means mountain chains; craton means an undisturbed continental center).

Running Winnie's Grotto Rapid.

Running the upper part of Disaster Falls, where the John Wesley Powell party lost a boat in 1869.

 Lower Disaster Falls.

The Uintah Mountain Group is on average between four and seven kilometers thick! That's about 24,000 feet. It certainly was a consistently subsiding basin during this time, likely the result of Australia pulling away from Laurentia.

As we progressed downstream, younger rock units descended down toward us. Our river journey was across the southern flank of the east-west trending Uintah upwarp. About midway through the red cliff is the contact with the Lodore Sandstone. This unconformity represents about 600 million years of time where no rocks are preserved. Unconformities are like pages ripped out the center of a book.

The upper part of Hell's Half Mile, a rapid also named by John Wesley Powell.

A stately juniper tree with its roots firmly set in the Uintah Mountain Group.

Although very similar in color, note the difference in bedding characteristics between the lower Uintah Mountain Group (blocky) and the overlying Lodore Sandstone (horizontally bedded). The next day, we would climb to the top of the back side of this cliff for a view upstream on the river.

There were dozens and dozens of Bighorn sheep seen on our trip and this individual was found resting in the sun next to our camp.

Sunset on the limestone cliffs above our camp at Limestone Draw. The upper cliff and intermediate slope are part of the Pennsylvanian age Morgan Formation (about 300 Ma) and the lower, partly shadowed cliff is in the Madison Limestone.

Bioturbation in the Lodore Sandstone looks similar to vertical worm burrows observed in the Tapeats Sandstone farther south. In fact, the Lodore Formation is a dead ringer for the Tapeats Ss. and in fact the two units are correlative, meaning they are the same age and deposited in the same depositional setting.

Note the angle of the beds in this north view, exposing the southern flank of the Uintah upwarp.

We are now almost on the brink of the overlook at the north end of the Limestone Draw campsite.

Voila! The Green River in all of its glory inside the Canyon of Lodore. Note the erosional remnant of Lodore Sandstone making a rectangular cap on top of the underlying Uintah Mountain Group just below and to the right of the photo center. This was an awesome hike!

On the way back someone found a coral fossil, likely eroded from the Madison Limestone above.

Nearing the Mitten Park fault, where beds of the Morgan Formation are upturned against the upthrown side (right). This signals our imminent arrival to Echo Park.

John Wesley Powell named this monolith Echo Rock, composed of Permian age Weber Sandstone. Today it is called Steamboat Rock. Desert tapestries cascade down the rock surface, forming when water drips down from above causing bacteria and lichens grow on the watered surface.

The confluence of the Yampa River, looking east. We were supposed to float the Yampa on this trip but the lack of a winter snowpack made the river unrunnable for our 18-foot rafts. This concludes the first half of the river trip.

Wednesday, June 27, 2018

Raft Trip in Dinosaur National Monument, Utah and Colorado Begins


I am up in Vernal Utah to begin a five-day float trip through the Canyon of Lodore, Whirlpool Canyon, and Split Mountain Canyon on the Green River. I'll be posting pictures and stories after I return on July 4.

Today I toured the Douglas Dinosaur Quarry, site of the 1909 discovery of a fabulous bone bed in the Morrison Formation and drove the Harpers Corner Road on top of Dinosaur. More pictures to follow after the trip.

The mouth of Split Mountain Canyon.

The Nugget Sandstone (bottom white bed) is the time equivalent of the Navajo Sandstone, is capped by a thin red deposit of Carmel Formation and an upper cliff of Estrada Sandstone on the way up the Harpers Corner Road.

Saturday, June 16, 2018

The 2018 AAPG Geosciences in the Media Award, Salt Lake City, Utah

On May 20, 2018, the American Association of Petroleum Geologists (AAPG) held their annual meeting in Salt Lake City, Utah. As I mentioned in a post previously (December 2 , 2017), the AAPG has granted the AAPG 2018 Geosciences in the Media Award to me for a lifetime body of work. What an honor it is to receive this award from such a prestigious organization.


A partial listing of past awardees in this category is shown below. What an impressive list and I am deeply humbled to become a part of this group:

John McPhee (1982 and 1987)
James Michener (1984)
Rod Redfern (1983 and 2003)
David Attenborough (1986)
Stephen Jay Gould (1993)
Jack Horner (1994)
Wallace Hansen (1995)
Donald Baars (1997)
Walter Alvarez (1998)
Sarah Andrews (1999)
Simon Winchester (2003)
Bill Bryson (2005)
Michael Crichton (2006)
Ron Blakey (2011)
Ben Gadd (2016)
Michael Collier (2017)

You can view all of the past awardees since the awards' origin in 1972 here.

I wish I could have accepted the award in person but was flying back home from Europe on May 20. Nevertheless, I am honored to receive this award. In 2014 and 2016 I received a similar award in the same category from the Rocky Mountain Association of Geologists for two of my books, Ancient Landscapes of the Colorado Plateau and Carving Grand Canyon.

More than viewing this simply as a personal award, I would like to thank the two organizations above who place high value in our field for recognizing professionals who choose a career path centered on the sharing of geology to a wider, public audience. Many awards , rightly go to those who perform original research. Yet our society benefits when they become better informed about all aspects of Earth's natural systems.

Geology surrounds each and every one of us, every day of our lives. Being better informed and in awe of the magnificent palette of geologic wonders makes for a more wholesome, adaptable and accepting society. Personally, I could have chosen the research path in geology as I loved field mapping. But my heart has always moved toward a path that involved sharing the wonders of earth history and earth processes with those who did not have the good fortune (as I have had) to study geology formally.

I would also like to thank my professors at Northern Arizona University who gave me the tools to think geologically. And to the many current researchers who share their findings with me. You are too numerous to mention here but I have learned from your results, incorporated them into my thinking and crafted them into a narrative that "regular" people find fascinating. Thank you one and all for your gifts!





Thursday, June 14, 2018

Comparing and Contrasting the June Hawai'i and Guatemala Volcanic Events

Eruption from Fissure 8 on June 10, 2018. Photo courtesy of County of Hawai'i Civil Defense Agency
Volcanic eruptions on the Big Island of Hawai'i and in Guatemala have recently taken center stage not only on the geologic front but in the national news as well. How do these two geologic settings compare and contrast?

Both locales are located in active volcanic zones and so eruptions are nothing new here. They both produce eruptions of lava and scoria (ash, pebble and boulder-size particles) that originate from magma within the crust. The term magma is used for melted rock still residing in the interior of the earth and the word lava is used when it finally erupts to the surface. That is the difference between those two words although occasionally you may hear reporters use each term in the opposite way.

Eruptive column from Volcano Fuego on June 3, 2018, image from Strange Sounds web site.
Guatemala

While the Hawai'ian eruptions are relatively gentle, the event that occurred in Guatemala on June 3, 2018 was quite explosive. To explain the difference between these two types of eruption styles, we need to look no further than the silica content contained in the different magma bodies. When more silica is contained in the melted rock, the more explosive eruptions can be. Silica adds viscosity (resistance to flow) to magma and the only way escape  route for the included gases found in all magma bodies is to explode violently. As the magma reaches near the surface, the gas expands, reaching a threshold and the only to escape the viscous substance is to explode outward. Thus the eruption on Fuego that sent a scoria cloud nearly 10 miles high.

Chart showing magma chemistry and resulting rock types, original from Wayne Ranney lecture slide 
The web site, Volcano Discovery has good, up-to-date information on Fuego's current activity. I also monitor the Smithsonian Global Volcanism Program for science information. These are both excellent sources but the Smithsonian site contains more detailed information. Check out the general information link on Fuego's home page for an interesting history of this volcano, including a reference to an earlier edifice that began growing on the same spot 230,000 years ago which collapsed in a massive debris-flow avalanche that ran 30 miles out into the Pacific Ocean! Check out this video from Knut Eisermann on FB for excellent footage of the June 3 eruption which, fortuitously for photographers, occurred around noon local time. The explosive eruption emitted ash and lava with a silica content of no less than 65% and as much as 75%. The rocks created from such chemistries are called dacite or rhyolite, respectively.

Three part diagram showing the assembly of the Central American microplate at 20 Ma, 12 Ma and 0 Ma (the present)
The setting of Guatemala is along the Pacific Ring of Fire, where ocean crust beneath the Pacific Ocean is sinking (geologists say subducting) beneath the edge of the Central American microcontinent. When this slab of ocean crust descends to between 60 and 100 miles, it begins to melt and then rises buoyantly through the crust. The subducting plate, called the Cocos plate, is rather long and melting along its edge causes these types of eruptions that occur from a line of volcanoes that stretch from central Mexico to northern South America. In reality, this geologic setting stretches intermittently from Alaska to Tierra del Fuego! Another great site to peruse about the scene in Guatemala on June 3 is called Strange Sounds and you can view images of it here.

Photo of Vulcan Fuego in January 24, 2017 from an area near the village of Esquintla, destroyed by the pyroclastic flow on June 3.  Photo by Don Webster
As a result of nearly 10-mile high scoria column, a deadly pyroclastic flow caused more than 100 human casualties and destroyed many villages around the perimeter of the volcano. Pyroclastic flows (literally fire fragments) are some of the most dangerous aspects from eruptions such as these. They form when rocks are blasted high into the atmosphere and then as they fall back to earth can be dense enough to trap escaping gases. The falling fragments, still glowing red hot, then ride downslope on a cushion of gas which lessens friction and the flows can reach speeds over 100 miles. See this NASA Earth Science web site that depicts the damaged areas as surveyed on June 4, 2018. This is part of their disaster program. One of the pyroclastic flows came through the valley where this photo was taken by a friend of mine in January 2017.

Kilauea

The Kilauea eruptions by contrast have become a rather benign spectacle because these eruption types are much less explosive. They issue  lavas with a lower silica content of around 45 to 55%. This is why we are all treated to fantastic images from helicopters and ground-based photographers who can approach the flows more closely and more readily. The rocks formed by magmas with this chemistry are called basalt and the many picturesque photos and videos of red-flowing lava rivers will ultimately cool to create basalt lava rock. (Basalt is the most common rock type on Earth's surface, covering up to 62% mostly on the ocean floors of the planet).

Hot spot track in cross-section, by Joel E. Robinson, USGS, via Wikimedia Commons
Hawai'i is situated over a hot spot in the mid-Pacific (see diagram above). The Pacific plate is slowly drifting northwest over this comparatively stationary hot plume, causing eruptions in Hawai'i to shift through time in the southeast direction. Think of a smoke stack at a factory as the stationary hot spot and the wind-drifted smoke column as the chain of volcanoes through time. Around 5 million years ago, the island of Kaua'i was positioned right over the current eruptive center. But as time has passed, this area has drifted northwest about 300 miles, riding on top of the Pacific plate. One day, the Big Island will also become volcanically dormant and new islands will be present to the southeast. In fact another volcano is nearing sea level from below and is already 13,000 feet high (but still about 3,000 feet below sea level). It is called Lo'ihi and can be seen on the far right in the diagram above. Lo'ihi will likely merge with the Big Island, or it could become a separate island.

Space view of Kilauea volcano and the newly formed Fissure 8. From Nature Journal, June 9, 2018
The modern hot spot resides beneath the Kilauea volcano on the Big Island. The nearby Mauna Loa volcano is not quite inactive yet, but has moved far enough away that eruptions today typically come from the Kilauea cone. Three other volcanoes exist to the northwest on the Big Island and are considered inactive due to plate drift away from the hot spot. Anyone who lives on the flanks of the Kilauea volcano knew that they were rolling the dice with respect to life and property. Whereas the Guatemala eruption killed over 100 people, no one had died from this eruption in Hawai'i. The relative lack of silica in these lavas is the reason. However, rivers of lava have destroyed over 700 homes and the pain and suffering involved with this natural event cannot be discounted.

Map of lava flow paths from Fissure 8, depicting the extent of lava flows on June 11.
 Note the new land that has formed as a result of this event. From
Lava flows from Fissure 8 entering the sea. From Dr. Larry Freisen, Santa Barbara City College.

A well-known coral reef was destroyed here in Kapoho Bay. From Dr. Larry Freisen, Santa Barbara City College.
Tools

There are incredible videos to watch and a few are listed here.

To see a live stream video linked to the website of the US Geological Survey, with real time images of the lava flow click this link here.

A helicopter overflight of Kapoho Bay from the USGS on June 5, 2018 around 5 PM HST can be seen here.

Really good helicopter photos of the lava overtaking roads, and homes being engulfed here.

Don't miss this one! A 15 minute video of driving to the lava front on the day 500 homes were lost in Kapoho Bay. Incredible footage here!

Also, friend Nancy from the Big Island sent a link to a blog from a local there who describes many of the included photos in native Hawai'ian themes here. Updated regularly.

Geology is dynamic as these two events show. All of these kinds of events have happened millions of times in the past and will continue into the future. Knowing how the earth works can help our society prepare for future perturbations in a world that we would like to be predictable. Geology informs society.