Nature News from GYE #15 Oct 18, 2020

Nature

The upswing in visitation to Yellowstone NP is starting to wane.  Nights are long, days are cooler and some travelers are returning home. Some are heading south.   2 months this summer Yellowstone experienced record visitation. The entire ecosystem was full of “covid refugees”.  People took advantage of this time to explore the country and many of the National Parks that did not close were on their travel agenda.  Some discovered locations within these parks they were not aware of.  One location in Yellowstone Park that surprises and delights travelers is the Grand Canyon of the Yellowstone River. 

The river flows to the north where it exits Yellowstone Lake at Fishing Bridge.  It winds its way through an area (called the Sour Creek Dome)  that is affected by the volcanically driven pressure.  This area has had measurable rising and subsiding at the surface for as long as USGS has recognized this activity.  It is not the only place in Yellowstone where this occurs.

Grand Canyon of the Yellowstone River, Steve Dolberg

The Yellowstone River continues north through the Hayden Valley and eventually enters an area where 3 ancient lava flows have solidified through time.  This is the location of the Grand Canyon.  The geologic history here is complex and not entirely understood as so many processes have played a role in the creation of this feature through time. One of these processes is volcanism which resulted in caldera formation (huge crater) that ultimately filled with magma.  At the same time, faulting occurred and some of this molten rock poured out of the fault lines to cover the surface of the canyon area in 8-10 different eras.  This is just a small percentage of lava flows occurring in the entire Yellowstone Ecosystem over the last 2 million years.

Fracturing and mineralization due to hydrothermal alteration, Tom Nicholls

Another result of the volcanic nature of this area, hydrothermal fluids (hot water) moving through fractures in the layers of rock were altering the hardness of the rock and encouraging formation of certain minerals that are seen on the surface today. (see above) Fracturing associated with these processes has encouraged the rock change more quickly. The erosion that has occurred in the hydrothermally altered rock is most visible today in the canyon walls below the Lower Falls of the Yellowstone. These 5 miles of the canyon are wider and deeper and more mineralized than anywhere else along the river’s path.  The canyon in total is over 20 miles in length, 1500-4000 ft wide and over 1000 feet deep.

Hashim Kindu, one of our long time guides on Tanzania trips, on his visit to Yellowstone, photo by Tom Nicholls

Prior to this, much longer ago, the Yellowstone River flowed in different locations.  The current drainage pattern of the river has been impacted by all the forces I have mentioned as well as glaciation. Glaciation has occurred probably 10 different times in the same time period.  The depth of this ice ranged from 11,000 feet to 7,000 feet.  As we know, glaciers are master sculptures and deposit much of what they pick up in locations far away from the origin. Most of the GYE has been altered due to  periodic ice ages.   Immediately following the last regional ice age (the Pinedale Glaciation ending approximately ending15,000 years ago) a significant amount of water, much more than today, was “ponding” ( being dammed up by glacial ice remnants or landslides)  and flowing in Yellowstone. 

Imagine of all this happening in geologically short period of time.  Eventually the location of the Grand Canyon today was impacted by immense amounts of water flooding through this area.  Water eroded the canyon as we see it today.  Some of the most exquisite and deepest and portion of the canyon below the Lower Falls is younger than the last glacial period!  Think about the idea that less than 15,000 ya the initial erosional process were beginning to carve this portion of the Grand Canyon in Yellowstone!

Lower Falls of the Grand Canyon, Steve Dolberg

The 308-foot Lower Falls formed where the river flows over volcanic rock more resistant to erosion than the downstream rocks, which are hydrothermally altered. Above is a photo of Lower Falls taken from Artist’s Point. This is a name given after a painting done by landscape artist, Thomas Moran who was with the 1871 Hayden Expedition. His many field sketches and later large paintings were some of the images that told the story of the magnificence and significance of Yellowstone as a unique place worthy of National Park Status. These images helped convince Congress to pass the Yellowstone Park Act, March 1, 1871 creating the “world’s first National Park”.

Lower Falls of Yellowstone by Thomas Moran

This painting is not an exact replica of what he saw, but created back in his studio to represent what he experienced at this place, after he returned from the journey. Below are a couple images of the Upper Falls of the Yellowstone River. The Upper Falls drop 109 feet and are located upstream of the Lower Falls.

Brink of Upper Falls from view point
The 109-foot Upper Falls flows over a similar type of more resistant or harder rock. 

July 13th “nature news” discussed Yellowstone as the source of large and mighty rivers. Located across the Continental Divide, the Park feeds two of the most extensive drainage systems in the nation; the Missouri River system (and ultimately the Mississippi River) on the Atlantic side, via the Yellowstone, Madison, and Gallatin Rivers, and the Columbia River system on the Pacific side, via the Snake River   With all this surface water flowing over a landscape impacted by volcanism and glaciation, the perfect conditions for waterfalls exist.

Many stretches of the main river valleys in Yellowstone are broad and flat bottomed. However, throughout the ecosystem streams and rivers often encounter corridors between the many lava flows.  These flows are different ages and some of them bumped into previously hardened flows.  Some bumped into glacial ice, and some have been altered by hydrothermal activity. All of this creates a perfect scenario for surface water running to find its way through the corridors between flows. When it encounters rock of different hardness, a waterfall or cascades begins to form. 

Yellowstone park reports at least 50 waterfalls that occur within the park, 25 of them fall over 100 feet.  One of your future trips to Yellowstone, consider exploring some of these waterfalls!  Snowmelt in the spring is the time the highest flows and drama occurs.  Each season has its own beauty, however.  Below are some other images of beautiful falls in Yellowstone. As you enjoy all of this, imagine, if you live anywhere in the Missouri River watershed or the Snake River, ultimately Columbia River watershed, these are all upstream from your home!

Fairy Falls in winter found in the Central Basin Lava flows
Gibbon Falls where the Gibbon River falls over the caldera rim
Firehole Falls seen along the Firehole Canyon drive

Firehole River and falls runs between 2 lava flows of 2 different ages. Below is the falls that occur at a “knickpoint” . A knickpoint is “part of a river or channel where there is a sharp change in channel slope, such as a waterfall or lake. Knickpoints reflect different conditions and processes on the river, often caused by previous erosion due to glaciation or variance in physical characteristics of rock.”

Kepler Cascades

Lastly is a view of Kepler Cascades which is a series of waterfalls that drop over 3 different benches of rhyolite rock between 100-150 feet. This is located in the Upper Basin Lava flow. Kepler Falls is named for Kepler Hoyt, the son of Governor John Hoyt. They visited this together in 1881 with some enlisted men and packers looking for a suitable route between Wyoming territory and this part of the recently formed Yellowstone Park.

So many lava flows with so much water and hence, so many waterfalls to explore. I have just scratched the surface.

Thanks for reading these. Wishing you all good days and good health. If you’d like to contact me, email me at lesliehstoltz@gmail.com.

Leslie

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