Yellowstone – What Makes it so Spectacular…It’s History

My History with Yellowstone

A half century ago, or so, was the first time I experienced Yellowstone. I was young and the specific memories of the trip are vague, but I do remember it being something very special. Growing up in the city, the vast waters of Yellowstone Lake and the majestic mountains and lodgepole pines as far as the eye could see was something I rarely saw. Wildlife like bison, elk and bear was a far cry from the occasional stray dog running through the neighborhood. It is just one of those places you “can’t unsee.” It was many years before I got the opportunity to return and I have made several trips in the last decade, mostly driven by the passion for photography and the desire to attempt to capture some of that spectacular scenery and wildlife. But in the last year, the history and geology has become increasingly fascinating and now I see the park in a whole new light. My history in the park is but a blink of the eye in the history of this amazing park. It is the greater history of this area that brings millions of folks every year to experience this place. A fascinating history it is.

Geologic History of Yellowstone

500-65 Million Years Ago – The early years

While my history in Yellowstone is measured in weeks over a span of tens of years, geologic history is measured in tens of thousands, millions and billions of years. If you go back between 100-500 million years, you would have found Yellowstone, to be near sea level. Sometimes it would be above sea level and sometimes below. Up until around 300 million years ago, the area was south of the equator. It’s plate tectonic journey eventually arriving in it’s current northern latitude around 70 million years ago. Sometimes the area would be under water in shallow seas, sometimes beach front or coastal property. There were times when the climate was dry and desert-like and sometimes very humid with an environment resembling the Everglades in Florida. Starting around 100 million years ago, the area was flooded by seawater with the Western Interior Seaway which continued for around 25-30 million years. This older history is described an earlier post, Western Wyoming Rocks. Much of this older history has been what we say, “overcome by events.” Deposits from the Western Interior Seaway or often called the Cretaceous Seaway can be seen north on a peak north of the Mammoth Hot Springs Area of the park.

65-55 Million Years Ago – Two continental plates collide and the mountains emerge

Around 65 million years ago, plate tectonics brought a new dimension to Yellowstone impacting much of the Rocky Mountain area. This mountain building event, called the Laramide Orogeny, brought on by the collision between the North American Plate and the Farallon Plate in the Pacific. This event, lasting around 10 million years, uplifted the Wind River Range to the south, the Big Horn Mountains to the east and the Beartooth Mountains that form the northern border of Yellowstone National Park. The Beartooth Mountains are largely in Southern Montana and not shown in the Wyoming map below.

53-43 Million Years Ago – Absaroka Volcanics

Had we made a visit to Yellowstone around 55 million years ago, it might very well have looked like the Green River, Wind River or Big Horn Basin looks today dominated by erosional deposits coming off the recently-uplifted mountains. But, closely on the heels of the Laramide Orogeny, starting around 53 million years ago, significant volcanic activity began in what is now Northwest Wyoming and continued for around 10 million years. This volcanic activity impacted many areas within the Rocky Mountains. In the Yellowstone area, it formed the Absaroka Mountains we see today.

Geologists divided the Absaroka volcanic activity into three distinct groups, the earliest being the Washburn Group. The Washburn Volcano, or at least part of it, is shown on the map above within the park boundaries. Later, the Sunlight Volcano became active and the “cone” is located north of the highway connecting the east gate and Cody, WY. Finally, rocks from the Thorofare Creek Group can be best seen north of the highway between Moran Junction in Grand Teton National Park and the town of Dubois, WY as well as areas within the Yellowstone NP boundaries. The Absaroka Range is an old relic of geologic past that happens to grace eastern Yellowstone with it’s natural beauty, it is not the volcanic activity that defines the park today…more to follow on that.

One other relic of the Absaroka volcanic activity on display in Yellowstone is the remnants of an ancient forest of redwood, sycamore, magnolia, dogwood and other trees. Volcanic activity combined heated groundwater with silica-rich ash and lava to generate large mudflows. These mudflows, while destroying the existing forest, did preserve their history in the form of petrified wood which can be seen on Specimen Ridge overlooking Lamar Valley.

10 Million Years Ago – The crust is spreading and mountains are building on the western front

Around 18 million years ago, the tectonic forces affecting the Western North American plate began to change. The southern part of the Farallon Plate was fully subducted under the North American plate and the forces that created the San Andreas Fault in Southern California began to have an impact on Western Wyoming. The plate compression during the Laramide Orogeny had now shifted to extension associated with the Basin and Range activity primarily affecting Nevada and Utah. The faulting that formed the Teton Range south of Yellowstone starting around 10 million years ago associated with that Basin and Range extension is likely similar to the faulting the formed the Gallatin Range in the NW corner of Yellowstone. The north-south trending Bridger Rangefront Fault that separates the Gallatin Mountains to the west and the Gardner River Valley to the east closely resembles the fault that formed the Teton Range and Jackson Hole valley.

2 Million Years to 70,000 Years Ago – The volcanics return…with a vengeance

While the Teton and Gallatin Ranges were building, the destructive forces that would eventually define Yellowstone were brewing in the Snake River Valley of Idaho. The North American continental plate was slowly moving to the southwest over the large magma pool in the same way that the Hawaiian Island chain is moving over the magma pool in the Pacific. The McDermitt Caldera in the image below would eventually become the Yellowstone Caldera that defined what we see today.

A little over two million years ago the magma pool found itself below Yellowstone and things in and around Yellowstone began to change, and change dramatically. The magma chamber underlying Yellowstone erupted in Eastern Idaho, just west of Yellowstone in what is believed to be one of the most powerful eruptions in earth’s history, on the order of 1,000 times the force of the Mt. St Helens eruption. Whatever existed in the immediate area above the exploding magma pool was obliterated. Nearing the end of the eruption, the overlying rock above the magma chamber collapsed into the chamber forming a caldera likely similar to what we see at Crater Lake in Oregon. The impacts from volcanic debris and ash were extensive, likely impacting significant portions of North America. Had nothing changed from that point on, the caldera may have filled with water like what happened to Crater Lake in the image below but it didn’t.

Unlike Crater lake, the magma pool below Yellowstone did not remain dormant. In fact, there were two more major eruptions from this pool of magma lying 1-3 miles below the surface. The eruption around 2.1 million years ago deposited a layer of rock named the “Huckleberry Ridge Ash. The eruptions that occurred 1.3 million years ago left behind the “Mesa Falls Ash” and 630,000 years ago depositing the “Lava Creek Ash”. Note, sometimes the geologic term “tuff” is used in place of “ash.”

So, the next logical question, why doesn’t the Yellowstone Caldera look like Crater Lake. As a matter of fact, when you drive through Yellowstone, it looks nothing like Crater Lake. There is almost no obvious, visible, evidence that there ever was a crater there. It’s not visible in Yellowstone because while the last major explosive eruption occurred around 630,000 years ago, volcanic activity continued until around 70,000 years ago filling the caldera with younger volcanic Rhyolite and Basalt flows.

The Yellowstone brochure map indicates the location of the latest caldera boundary. Lewis Falls and Gibbon Falls are two places the caldera rim are exposed as water flows over the edge of the caldera rim. More dramatically, the southern half of the Washburn Volcano (Absaroka volcanics) collapsed into the caldera during the last major eruption 630,000 years ago.

Well, that’s a pretty amazing history…are we done yet? Not quite. What could easily be described as hell on earth for the last couple million years hasn’t frozen over yet, but it’s fixin’ to. Enter the ice ages.

The Ice Ages – Let the sculpting begin

Geologists refer to the time from 2.58 million years ago to 11,700 years ago as the Pleistocene Epoch…the Ice Ages. Since the last major volcanic eruption in Yellowstone, ice core records show many period of warming and cooling as depicted in the graph below. The red box on the right edge of the graph below indicates the temperature records since the last major glacial period which peaked around 20,000 years ago.

Evidence suggests that, in addition to the dramatic volcanic explosions, Yellowstone experienced the big chill and was likely blanketed by glaciers on multiple occasions in the last 400,000 years as illustrated below. These glaciers carved and shaped the basic landscape we see today.

A significant amount of evidence of glacial activity exists in the park. Sadly, I didn’t have this post in mind at the time and wasn’t looking to specifically capture that evidence. Having said that, here are a couple of images of classic glacial sculptures in the areas surrounding the park.

With elevations at or above 7,000′, Yellowstone gets plenty of snow throughout the year. We got snowed on in June, this year. Between the 1400s and 1800’s, the “Little Ice Age” formed glaciers in many surrounding mountain areas including the Tetons and Glacier National Park. It’s unknown how Yellowstone was impacted by this recent cooling event.

The Geologic Journey Continues

Yellowstone Lake is a natural lake, there are no dams or man-made features that control water flow in and out of the lake. Fishing Bridge on the north side of Yellowstone Lake is where the Yellowstone River begins it’s journey to join the Missouri River, then the Mississippi River to the Gulf of Mexico. After flowing north from the lake, it crosses Hayden Valley, drops over the Upper Falls, then the Lower Falls (seen below) into the Grand Canyon of the Yellowstone. The massive flow along this river is largely responsible for forming this spectacular canyon. The Rhyolite volcanic rocks on the canyon walls are part of the volcanic activity that occurred after the last major eruption, filling in the canyon. The unique yellow, red and orange coloring on the canyon walls resulted from the rock being hydrothermally altered, then oxidized as it was exposed to the elements…another way of saying hot water changed the rock and it got left out and rusted. 🙂

The hot springs in the Mammoth Hot Springs area are another place where you can see geologic change happen before your eyes. Rainfall gets into the groundwater system, sinks down through the underground piping system and gets heated and mixed with carbon dioxide from the underground magma system to form carbonic acid. The warm water then rises, dissolving some of the limestone from layers formed several hundred million years ago. The liquid, now kinda like hard water on steroids rises to the surface and once reaching the surface, flows over the thermal features. The carbon dioxide escapes into the air and the “hard water” deposits leave behind layers of the rock, Travertine, which is what we see forming these rock ledges. Tons of travertine are deposited each day. The colors we see are not the rock but rather the algae growing on the rock (color depends on the water temperature and heat tolerance of the various forms of algae).

The geysers, hot springs, mud pots and fumarole’s (steam vents). A massive underground water system just doing it’s thing. Geysers erupt when superheated water, under pressure, finally lets the pressure go. Beautiful hot springs, adorned with temperature sensitive algae. The smell of rotten eggs (it’s an acquired smell, by the way) as hydrogen sulfate escapes into the air from the mudpots, and the hissing sound of steam coming out of fumarole’s. It’s all what we go there to see!!

To give you an idea of the geologic diversity you will encounter. If you depart the Madison Junction and head towards Norris, you will follow the Gibbon River to Gibbon falls. Along that drive your will climb out of the caldera to top the rim at the Gibbon Falls. You will see the Lava Creek Tuff to the left deposited 630,000 years ago during the last major eruption, the younger Rhyolite lava that filled in the caldera to the right. The Norris Geyser Basin is like a “hot blister” on the surface and contains the current hottest and most active thermal features. As you head north from Norris to Mammoth, you will drive through the Lava Creek Tuff, be able to view obsidian rock (volcanic glass) at Obsidian Cliffs, relatively recent columnar basalt flows at Sheepeater Cliff. At the Swan Lake Pullout, you can look west across the Gardner River Valley to see layers of rock ranging from billions of years old through the time dinosaurs roamed the earth, uplifted by faulting 10 millions years ago. As you pass through the “Golden Gate,” you will be driving through layers of the Huckleberry Ridge Tuff (2.1 million year old volcanics) and view Bunson Peak to the right, a volcanic plug from the Absaroka Volcanics, 50 million years ago. As you drop down into the valley, you pass through large travertine blocks overlaying shales deposited 70+ million years ago when the interior of the continent was flooded by seawater. When you reach the Mammoth Hot Springs, you can watch rocks being formed right before your eyes….and that is just the start!!

Human History

Human history in Yellowstone likely goes no further back than around 11,000 years. Prior to that, the area was buried under massive glaciers for tens, if not hundreds of thousands of years. Native American tribes certainly spent time in the area but because of the extreme winter temperatures and snow fall, likely this was no more than a temporary summer home or hunting ground. Up until the early 1800’s, Native Americans are the only known humans to see the Yellowstone area with tribal backgrounds including; Shoshoni, Crow, Blackfeet in the immediate area and likely Nez Perce, Gros Ventre and Flathead in the surrounding areas.

In 1805, the Lewis and Clark Corps of Discovery Expedition passed north of the Yellowstone area heading westbound and passed again, headed eastbound in 1806. William Clark split off to follow the Yellowstone River eastbound through Montana on the return trip but the team never saw Yellowstone itself. One team member, John Colter, split off the expedition in the final stage. For the next few years, he explored the areas in and around Yellowstone. His description of Yellowstone was often referred to as “Colter’s Hell.” He is believed to be the first white explorer to ever lay eyes on what would become Yellowstone National Park over 60 years later.

For the next half century, the only people to spend time in Yellowstone were Native Americans and a handful of fur trappers and traders including; Jim Bridger, Hugh Glass, Joseph Meek, Thomas Fitzpatrick and the Sublette brothers, William and Milton. Jim Bridger, know for his wild tales (truth often measured in percentages) sparking interest in the area. The Homestead Act of 1862 sparked a large westward movement but the area surrounding Yellowstone was not conducive to farming nor an attraction to miners so it didn’t see a significant influx of homesteaders until the 1890s.

In 1869, the entrepreneurial spirit began to recognize the Yellowstone area and for the next few years, formal expeditions were formed to explore and document the area. Early expeditions including the Cook-Folsom-Peterson formed in the Montana Territory likely to find natural resources (gold mining was quite popular). It’s likely they found little mining opportunity since the following year the Washburn-Langford-Doane Expedition emerged with a slightly different story. On the Washburn Expedition, team member Nathaniel P. Langford was a businessman, connected to Jay Cooke of the Northern Pacific Railroad. Following the expedition, Cooke financed Langford to travel around telling the story of the grandeur he saw to entice people to visit the area…I assume by rail. One of those inspired was a geologist named Ferdinand Hayden who led the Hayden Expedition in 1872. His team included an artist Thomas Moran and a photographer, William Jackson. The art and photography that emerged, presented to congress, led to the formation of Yellowstone National Park in 1872. Interestingly, Wyoming became a state in 1890, 18 years later.

The National Park Service wasn’t created until 1916. Without any appropriation (money) or guidance, Yellowstone languished and began to feel the adverse affects of unrestrained tourism. General Phillip Sheridan recognized this natural treasure and stepped up with the U.S. Army to find a way to take care of Yellowstone. Today, people flock to see the park but back in the day, this wasn’t necessarily consider a desirable military assignment. The Army attended to the park for the next 32 years. One notable superintendent of Yellowstone was Horace Albright who, as an assistant to Stephen Mather, founded and built the National Park Service.

This historical overview above only scratches the surface of Yellowstone’s history and the people who made it famous. For fun, search Truman C. Everts and his time spent in Yellowstone, quite the story.

The Wildlife History

The formation of the national park put a strong emphasis on protecting the wildlife and help the millions of visitors that have visited the park from “loving it to death.” This is an amazing story and books have been written on this. They have done a great job and deserve many thanks! Without going into great detail, here are a few parting wildlife shots. Two safety tips; zoom lenses are a wonderful thing and don’t pet the bison! Maintain a safe and respectful distance!!

Thanks for reading! Enjoy your visit!!

P.S. I know the rock names make this harder to understand. If you are interested, this may help. Here’s a quick explanation of igneous rocks…they all formed from magma. There are two general types of igneous rocks. The first type is plutonic (intrusive) where the magma cools (rock formed) below the earth’s surface. Granite is a classic plutonic rock. The second type is volcanic (extrusive) where the magma makes it to the surface, becomes lava (or ash) and cools (becomes rock) at or above the earth’s surface.

Igneous rocks are generally classified based on the mineral composition and origin (intrusive or extrusive). When the magma crystallizes (cools) below the surface, it takes longer to cool and the crystals are larger, the quicker the cooling the smaller the crystals. Obsidian cools very rapidly, the crystals are microscopic. It’s kinda like wine. You have red wine and white wine. Within those basic classifications you have Cabernet Sauvignon, Merlot, Pinot Noir as reds, and Chardonnay, Riesling, etc. for the white wines. A “pink” wine might be considered an “intermediate” option. They are all made of grapes. Different grapes, different wines.

Here’s a chart of how igneous rocks are generally classified followed by a diagram of how the magma plumbing works. On the chart, notice Rhyolite is formed from a similar mineral composition as Granite. Granite cooled below the surface (and subsequently uplifted to be exposed), Rhyolite was magma that breached the surface to become lava (either blasted out or flowed out) then cooled above ground.

The minerals that make up igneous rocks. If you haven’t fallen asleep, this will do the trick!! 🙂

Good Day!! 🙂

References: Yellowstone, The Story Behind the Scenery by Roger Anderson and Carol Shively Anderson, Fourteenth Printing, 2006, KC Publications. “Earth Science” by Tarbuck, Lutgens, and Tasa, Twelfth Edition, 2009, Pearson Education, Inc. “Roadside Geology of Wyoming” by David R. Lageson and Darwin R. Spearing, Revised 2nd Edition, Mountain Press Publishing Company, 1998. Several internet sources including the NPS website Yellowstone National Park (U.S. National Park Service) (nps.gov)