Sunday, September 16, 2018

2018 Grand Canyon Association Field Institute 10-Day Colorado River Trip

Every year for the last six years I have served as a geologic interpreter on a 10-day motorized river trip for the Grand Canyon Association Field Institute. The trip is meant to share the geologic wonders of the great gorge with GCA members who support the mission of the Association. By their nature, GCA members come to the trip already in love with the landscape of Grand Canyon but may want to delve deeper into its fascinating origin.

This year I did not take any of my own photographs. So what you will see here are a selection of photos I am using from two participants, Patrick and Barbara McGuffey. I thank them both for allowing me to use their photos in narrating this posting.

We often stop on the east side of Navajo Bridge (completed in 1929) which is now used as a viewpoint of the river 400 feet below. The new bridge (barely visible on the far left) was completed in 1995, making the old bridge accessible for pedestrians. I remember how for twenty years we drove across this narrow (18 feet) patch of concrete.

View upstream from Navajo Bridge. At this location, the river has incised down through the Kaibab Limestone (upper cliff) and the Toroweap Formation (lower, talus covered slope). Directly beneath the bridge (not seen here) are the first exposures of the Coconino Sandstone, only about 20 feet or so thick in this location. The Coconino thickens to the south and thins to the north.

While on Navajo Bridge, someone in our group spied California condor #54, roosting on one the bridge struts. What a treat.

We began our river trip - with a hike! This is a downstream view of the Colorado River at Lees Ferry. We are standing on the Shinarump Conglomerate Member of the Chinle Formation (foreground). The same stratum is also visible across the river as the short, shadowed cliff in the photo center. The tilt in the strata is attributable to the Echo Cliffs monocline, which is over 100 miles long and passes beneath this area. The deep red Moenkopi Formation lies beneath the Shinarump cliff down to the rivers' edge, while the slopes above that cliff are composed of the remainder of the Chinle Fm. and the Moenave and Kayenta formations. All of this is capped by the Navajo Sandstone on the far left. Note the large debris fan entering the river at right center. This is from the Paria River, which enters the Colorado on the far right. It is one of only five streams that enter the Grand Canyon from outside of it.

Just a little more than 12 miles into the canyon, the river has sliced into the Kaibab, Toroweap, Coconino, Hermit and Supai** formations. The top of the Supai is within the cross-bedded sandstone at river level on the right center. (** I have increasingly been a proponent of returning to the original name of the Supai Group back to Supai Formation. The individual formations within the Group are difficult to differentiate and unnecessarily confuse the stratigraphic column for educators and students. We'll see if this attempt will take hold with other interpreters in the canyon).

A Common side-blotched lizard (Uta stansburiana) perches on a rock in the mouth of North Canyon.

Sacred datura (Datura wrightii) was blooming just about everywhere we stopped on this trip. I have noticed it blooming frequently at the end of the monsoon season. Guests have mentioned to me that they appreciate my occasional musings into the extra-geologic aspects of the canyon's natural history. I attribute my interest in the plants and reptiles of the canyon to my years serving as a backcountry ranger and trail guide. However, if I don't get many questions, my tendency is to revert to exclusive geologic commentary.

A typical river camp with tables in the kitchen and chairs for guests to enjoy the view.

Hiking in the Grand Canyon is a different beast and river guides are often at a loss to describe the nature of hikes away from the river. Most hikes do not involve a lot of miles but there is extremely varied terrain that is often in and out of water. Short and steep rocky sections are the norm. Sometimes, these short but difficult stretches turn away the otherwise interested hiker. But if one perseveres through no more than 5 or 10 or 15 minutes of "pain" (typically) the rewards are great.

Our head guide with Arizona Raft Adventures (AzRA), Laura Fallon, showed me this fossil in the Supai on the hike up North Canyon. There are many root casts to be seen in this canyon but she showed me this one that was described to her by another geologist as possibly being a horse-tail (Equisetum). These plants have been around since the Devonian some 375 million years ago (375 Ma) and the Supai here is no older than 316 Ma. It was segmented like Equisetum.

The "narrows" in North Canyon. Note the exfoliated shape in the textures of the canyon walls. As the rocks were progressively removed by countless flash floods, the pressure that once kept them tightly packed was also removed. What follows are fractures that develop parallel to the open space.

Slicing downwards into the Mississippian Redwall Limestone, a dissected cavern system is exposed. Directly opposite this cave on the opposite bank is another cave with similar dimensions. The idea is that the cave system was formed before the river exposed it. Note the lens-shaped light patch on the far right. This is a cave that is choked with Redwall Ls. rubble.

Stanton's Cave was named for Robert Brewster Stanton who was the first person after J.W. Powell to complete a Grand Canyon river trip. In 1889 three members in his party were drowned before they were 25 miles into the Grand Canyon. So the next year in 1890, Stanton returned to finish the surveying through the entire canyon for the proposed Denver, Colorado Canyons, and Pacific Railroad. Thankfully, it never was built.

Note the dark and light-colored banding in the Redwall near South Canyon. Our assistant raft guide, Elisabeth McGuirk, shared with me a paper she obtained from Dr. Gary Gianniny of Ft. Lewis College in Durango. Colorado. He made numerous thin sections of the rock, (where slices of rock only 3/1000s of an inch thick are studied under polarized and unpolarized light to determine their make-up). He found that the dark bands were composed very porous dolomite mudstone layers having up to 35% porosity (average 18%) with the lighter bands being less porous and composed of crinoidal and oolitic calcite grainstone. His work shows that the Redwall trends from deeper water settings below and grades upwards into shallower environments.

We saw many Desert bighorn sheep (Ovis canadensis nelsonii) on this trip, as the rams were busy assembling their autumn harems. Here a big ram (center) leads four ewes up the slope.

Our green water trip ended when we encountered the Little Colorado River at River Mile 62. Recent rains had turned the LCR a chocolate brown color and later on our trip became even more muddy, or as we say, sediment rich.

Just downstream from the LCR.

Looking up nearly 1,000 feet to the contact of the dark Precambrian crystalline rocks (below) with the light brown, Cambrian Tapeats Sandstone capping it. In the Grand Canyon, this is known as The Great Unconformity. I typically tell guests to strain their necks to look up and see the contact so far above their heads, since the contact will eventually return back to river level in a day or two. This is an educational technique I use to explain warping in the layers.

Near River Mile 108, pink intrusive dikes of the Zoroaster Granite penetrate the dark Vishnu Schist. The Great Unconformity caps it all.

This double rainbow signaled the end of a two-day period of summer rain we enjoyed while traveling down the river. It was spectacular.

The Powell Plateau receives morning light as our group enjoys breakfast by the river. We spent the entire day meandering around this isolated spur in the heart of the Grand Canyon.

To explain the previous caption and photo, I include this section of the geologic map of Grand Canyon. The yellow arrow denotes the direction of the previous photo and the two circles denote the two camps. Note how the river makes huge, sweeping loops around the Powell Plateau. One night we looked west to the east side of the Plateau; the next we looked east to its west side! The river flows 28 miles in this stretch.

With the river flowing south here near River Mile 114, it moves around the eastern side of the Powell Plateau.

At last! The Great Unconformity is attained at River Mile 121 in Blacktail Canyon. Here Liz's hand is on the Tapeats Sandstone with her foot near the Prescambrian crystalline rocks.

Another guest, Ann, has her finger right on the contact. 1,200 million years of the rock record is missing at this contact. However, something can be known about what happened during this long span of geologic history (more than 1/4 of all Earth history). That is because isolated remnants of a thick stack of sedimentary rocks escaped complete erosion and destruction in other parts of the Grand Canyon. Because of that fortuitous preservation we know what happened during large portion of this history.

Real men (well, at least the older ones) wear sarongs on these river trips. It helps keeps the intense sun off of ones legs.

Entering "the Ice Box", a section of the river trip where limestone and sandstone walls rise nearly 3,000 feet vertically to block out much of the sun in this stretch. This is a downstream view.

And an upstream view where Laura and Lis converse about the river. Or our schedule. Or the beauty of the Grand Canyon.

Within the Ice Box, there are many seeps and springs that harbor endemic species of plants and animals. This one was at our Ledge Camp at River Mile 152.

One of the joys I have experienced in leading these trips is running into other guides whom I know from guide gatherings and lectures. It is wonderful to meet friends in the middle of nowhere.

Barry has found a comfortable seat in an eroded patch of travertine in Havasu Canyon.

Trip leader Laura Fallon giving one of her readings during an especially quiet stretch of the river.

On the horizon in the distance is Toroweap Point on the North Rim. I will be leading two trips to Toroweap in October traveling overland across the famous 62 mile-long road.

The Red Slide is a curiosity at River Mile 175. Huge pillars of loose rocky debris are capped by boulders all seemingly derived from the Supai Formation cliff above. There doesn't appear to be much (if any) Redwall debris in the mix - although a Redwall cliff is also exposed upslope. I have noticed there may be two different deposits here of different ages, with one sitting on top of the other. Someone will have to figure out the sequence of events here one day.

Vulcan's Anvil signals our arrival to the 'recent' lava section of the river trip. This remnant is interpreted as the site of a volcanic vent - right in the river corridor! A nearby dike and sill suggest that the volcano that grew within the channel of the river may have been quite high. It boggles the mind!

Downstream from Lava Falls, a side canyon in the south wall is filled with hardened basalt rock. Note the new canyon being carved to the right of the black fill. If the Colorado River had a motto, it would be, "No obstacles allowed!".

I snapped this picture of our group (sans guides, who were busy with camp chores) with Patrick's camera. Thank you all for being such wonderful river mates! And thank you for supporting the Grand Canyon Association! Thanks also to AzRA and Laura and Lis for giving us an excellent trip! Write me at wayneranney17@gmail.com if you are interested in any of my upcoming river trips or visit www.wayneranney.com.

Wednesday, September 12, 2018

Hurricane Florence



Check out the graphics within this Washington Post story from September 12, 2018. The video that shows the birth of Hurricane Florence off the western Sahara Desert is amazing! Note that two other systems follow Florence - Issac and Helene. Their ultimate destinations are as yet unknown but a triple whammy is not out of the question.

PS - For some reason, the video loop that shows the track of Hurricane Florence across the whole Atlantic within this article is not displaying in the link provided. Hope you can see it though when you click on the link.

Sunday, August 26, 2018

Icelands North and West Coasts

On a trip like this, I usually take hundreds and hundreds of photos and going through them afterwards are both rewarding and time-consuming. Most often I choose only photos that are well composed and exposed to include in a blog posting. However, other times I want to express a particular thought or emotion from the trip. In this posting, there is a combination of the two. And I sometimes question why I lug around 8 pounds of camera gear repeatedly to the same place. To which a ready answer does come to mind - it is never the same! Time of day, time of year, time of life. It's always different.

I just love boiling mud pots! Maybe it is the boy in me wanting to get dirty. Here at Namafjall, the Icelandic rift creates near surface geothermal heat that boils groundwater, which in turn chemically weathers the silica rock below. The result is silica and clay mud mixed with boiling water.

The gurgling and plop of the mud creates an another world feeling in the observer. Plus the smell of the Earth's interior! Our local guide warned us of the rotten egg smell, to which I added, some overcooked hard-boiled eggs have the same smell of the interior of the earth - breathe deep and enjoy its exotic nature! Okay, I go overboard sometimes. But no need to hate it off the bat without first giving it a chance to thrill the soul.

You have to take a lot of pictures to get the four boils going up at once.

A steam vent adds a sense of motion to the scene.

Up close the steam is hot to the touch. Ones skin could not take more than two seconds exposed to its heat and speed. It hisses loudly as the steam escapes.

Note the yellow sulphur deposits that precipitate near the vent.

Next stop was Dimmuborgir near the shores of Lake Myvatn. Dimmu (dark) borgir (cities of castles) literally means the dark castles. It is a fantastic area that never ceases to amaze. But the geologic story is the true champion here. About 2,300 years ago (i.e. not that long ago but before people lived in Iceland) a lava flow came to rest on top of a shallow basin that held marsh, water forming a large lava lake about 30-40 feet deep. The top of the lava pool cooled forming a rocky crust. But on the inside, red hot lava was still heating the marshy ground below until steam began to shoot upwards through the hot lava. The vertical steam vents caused nearby portions of the lava lake to cool more quickly. Without warning, the lava drained away, collapsing the roof and leaving the steam vents standing like dark castles. An amazing place and story to go with it.
I had never noticed it before this trip but we saw a vertical steam vent in the middle of one of the "castles." It is just below the rounded pinnacle on the right and trends downward into the top of the trees.

Numerous windows are carved into the castles as well.

Leaving Lake Myvatn, we passed Godafoss, another impressive Icelandic waterfall.

The parking area has been recently upgraded here from a muddy pit to a nicely paved lot with wide, meandering trails to the falls. As this is right on the Ring Road and lies between Akureyri and Lake Myvatn, Godafoss sees a lot of visitors. Note the small lava tube across the way.

Zooming into the wall near the lava tube across the way (I have a 300 mm lens), I spied a very interesting set of textures. You will note two different textures are present - an upper regular set of vertically oriented columns, and a lower irregular oriented set of columns. The upper textures form what is called the colonnade and the lower part is called the entablature. The colonnade textures form in the absence of water while the entablature textures form when water seeps into and interacts with the cooling lava. But I never before noticed where a colonnade rests on top of the entablature. What could this be?

An even closer view reveals a possible explanation. Note the way the entablature fractures seem to emanate from a single central vertical fracture. I presume that when this lava flow came to rest here, it did so on top of wet ground. As the lava heated the water below, it formed steam which rose upwards. The steam channel started the cooling process in the lava - the fractures always form perpendicular to the cooling surface. It looks like the steam eventually was all "used up," allowing a colonnade to form on top. I'm telling you, stay here long enough and many insights begin to reveal themselves. It is a natural laboratory for earth processes! Although the above description is pure speculation on my part, I have been learning more such features in my travels here.

On the road in the afternoon sun near Akureyri along the east side of Eyjafjörđur (Island Fjord). This is one of my favorite drives in Iceland as the sun always seems to be not far away.

Leaving Akureryi and driving up into the mountains.

In Iceland in the summer, one sees many of these plastic wrapped bales of hay for winter silage. The bales are wrapped in different colors.

This is the Öxandalur Valley, birthplace of the famous Icelandic poet Jonas Hallgrimsson. Actually "dalur" means valley in Icelandic (dalur equals "dale" in English) so it is redundant. Note the sharp mountain peak in the background.

This is Hraundrangi. It is an iconic mountain in Iceland but is usually in cloud. This was the best view I ever had of it. A quick glance might suggest that the peak formed as a cirque from glacial times. However, a wider view shows evidence for a catastrophic landslide here since the end of the Ice Age and what we are seeing the photo here is the headwall of the landslide.

Here is the rubble field to the south of Hraundrangi. Wow! What a difference the sun can make.

Although not native to Iceland, these daisy's were a welcome sight!

We spent the night in place not known for tourists - Sauđárkrókur. It is located along the Skagafjordur. This view is to the north toward the Arctic Circle.

The black sand beach at Sauđárkrókur.

Another location where we saw the debris field of a gigantic, post-glacial landslide. On the 8th of July this year, a very large landslide occurred in Iceland. Check out the AGU web site here for some incredible photos. These are still a very real thing in Iceland. I found a seven minute video that shows drone footage of this slide here. There may be a short ad to watch in Icelandic but you'll see the command in the lower right to skip after a few seconds. Wow!

What a day! August 11, 2018.

I had never before seen Eíriksjökull - it always so gray and cloudy in this part of Iceland. But look at this view.
Next was a visit to Grábrók, found right along the Ring Road. After making the short climb to top of Grábrók (on a constructed trail), we could see one of the other two nearby volcanoes, Grábrókarfell.

Birch twigs were recovered from inside the flows here in the early 2000s and they revealed a radiocarbon age of about 1,800 years ago - still about 670 years too early for people to have witnessed these erupting.

This is where a lava flow emanated to the surface from inside the cinder cone. Note the extent of the flow in the right distance - evident from the lighter-colored moss covering it. The trail to the top takes advantage of this lava flow, switchbacking up its spine.
Another amazing stop along the way is Hraunfossar (literally, Lava Falls). Hundreds of springs flow to the surface here into the Hvítá River, made blue from glacial flour (ice-pulverized rock).

Note how the springs all come from the same horizon. About 2,000 years ago a very porous aa lava flow covered an older, more dense flow below. The pre space in the upper flow acts as a conduit for Hvítá River water from farther upstream, where the river flows up against the young lava flow. The upper flow becomes saturated with water, creating the falls. The falls erupt here because the upper flow is nearing its distal end and the water is forced out.

Iceland is a land of tunnels! Tunnels under basalt ridges, mountain, fjords. Yes fjords. This tunnel, the Hvalfjörđur Tunnel, is almost 4 miles long and is about 540 feet below sea at its deepest point. The minimum amount of rock covering is 130 feet.

I had never before noticed so many landslides in Iceland. Perhaps it was the clear weather (likely). Or perhaps it tis my growing awareness of their ubiquity upon earth's landscapes (definitely). This may or may not be a landslide scar - it is very close to the sea and so may be a place where waves once washed against and eroded the cliff. Isostatic rebound has now caused the beach terrace to rise about 30 feet above the old seabed.

Guđaberg on the Snæfellsnes Peninsula is a favorite stop of mine.

Recent cinder cone formation left this impressive cone and flow to the east of it.

Note how the waterfalls just seem to appear our of nowhere in this view. The lighter-colored slopes are from mosses growing on quite recent lava flows. Like at Hraunfossar above, this flows were porous and act like sponges for water. When they encounter more dense flows below, the water is forced out suddenly. One can imagine how ancestral peoples would be baffled by such "magic." It doesn't take much more to understand the roots of some of our ancestral beliefs.

Iceland is a land of waterfalls, basalt lava, sea cliffs, and nature. I highly recommend a visit - just do not expect great weather at any time of year. For the geologist, it is a 'must see' place.

The old church at Buđir. Thank you as always for reading!