Yellowstone Elk: Conservation and Management

 Figure 1. Bull elk with cows (photo: Gallatin Wildlife Association).

ELK IN THE GREATER YELLOWSTONE

The Greater Yellowstone Ecosystem (GYE) is home to approximately 30,000–40,000 elk. Nine discrete herds, totaling 10,000-20,000 animals compose the Greater Yellowstone “superherd” whose summer range is in the core protected area of the GYE. Come winter, the majority of these animals will migrate to lower elevations, outside the park, while some will remain in the same area year-round. The timing and routes of elk migration closely follow the areas of seasonal vegetation growth and changes in snow depth. After winters with high snowpack, elk delay their vernal migration while in years with lower snowpack and earlier vegetation green-up, elk migrate earlier. There is growing evidence that elk are changing their migratory habits in response to predators: bears, wolves, mountain lions and human hunters. Figure 2 depicts the general location and migratory routes of the nine elk herds, each named for where they winter.

The dynamics of the Paradise Valley herd is highly dependent on private lands and its seasonal migrations have become more constrained. The Northern Herd is the best known and studied herd (along with the Jackson Herd), and the impact of wolves and hunting on population numbers continues to be sharply debated. The Madison Herd summers in and around the Madison Range, and winters in large groups on the high benchlands of the Madison Valley.

Figure 2. Nine distinct herds comprise the Yellowstone Superherd. Research by Arthur Middleton. Map by National Geographic (May 2016).

BIOLOGY/ECOLOGY

Elk (Cervus elaphus) are one of the most abundant large mammals found in the GYE, and they are a vital contributor to the ecology of the region: as prey for large carnivores, carrion for scavengers, and consumers of vegetation. Elk are also an economic mainstay for hunting and tourism in the states of Montana, Wyoming, and Idaho. It is not an overstatement that elk define and unify the GYE, both ecologically and culturally.

While North American’s elk is the same species as Europe’s red deer, the name “elk” is actually the European word for moose. Small wonder that European visitors can get confused on visiting Yellowstone. The species is perhaps better labelled “wapiti,” Shawnee for “white deer” or “white-rumped deer.”

Bull elk weigh about 700 pounds and stand some five feet high at the shoulder; cow elk weigh some 500 pounds and are slightly shorter. Calves are about 30 pounds at birth; born May to late-June, overlapping with periods of peak vegetation green-up and high-nutrition plant phases allowing mothers and calves to build up fat reserves. Elk feed on grasses, sedges, other herbs and shrubs, as well of aspen sprouts and bark, conifer needles, and aquatic plants.

In the fall, bull elk bugle to attract cows and challenge other bulls for dominance. The bugle is not so much a bugle coming from a brass horn as a bellow building to a squeal, terminating in a grunt (listen at https://elknetwork.com/elkfacts/). Dominant bulls gather cows and calves into small groups or harems and then aggressively guard these harems against all comers.

ANTLER MANIA

Bull elk grow massive racks which begin growing in the spring in response to a depression of testosterone levels and lengthening daylight. Yearling bulls grow antlers for about 90 days while healthy, mature bulls grow theirs over a +/- 140 day period. In the later stage of growth, antlers of a mature bull will grow 0.66 inches per day reaching 60” or more in length and weighing some 30 pounds per pair. During much of the summer, “velvet” covers the antlers -- a thick, fuzzy coating of skin, which nourishes and deposits the calcium that forms the antler. Antler growth typically ends in early August, and the bulls begin scraping the velvet off, polishing and sharpening the antler tines in preparation for the coming rut (mating season) in September and October.

Bulls retain their antlers through the winter. When antlered, bulls usually settle disputes by wrestling with their racks. When antlerless, they use their front hooves (as cows do), which is more likely to result in injury to one of the combatants. Because bulls spend the winter with other bulls or with gender-mixed herds, retaining antlers means fewer injuries sustained overall. Also, bulls with large antlers that are retained longer are at the top of elk social structure, allowing them preferential access to feeding sites and mates. Antlers are dropped annually, in March-April, and the process begins anew.

NORTHERN HERD DYNAMICS

The Northern Elk Herd is Yellowstone’s largest herd. Its summer range is centered in the area of the Lamar and Yellowstone river valleys, north of Yellowstone Lake, from Soda Butte to Gardiner, Montana. In winter the herd migrates north outside of the park into the Gallatin National Forest and the lower elevation private lands. With more moderate temperatures and less snowfall than the park interior, the Paradise Valley and surrounds supports large numbers of wintering elk. 

Figure 3. Winter counts of the Northern Elk Herd in Yellowstone National Park and adjacent areas of Montana, 1960–2016. Counts are not adjusted for elk sightability, and gaps represent years where no official count was conducted. Source: NPS.

For decades, debate raged over too many elk and the disappearance of willow and aspen from the Lamar Valley and elsewhere. Control of a burgeoning elk population was one of the main arguments for returning the gray wolf as it would provide a year-round predator to control elk numbers and keep them more dispersed across the landscape.

The winter count was approximately 17,000 when wolf reintroduction began in 1995. The number fell below 10,000 in 2003 and 3,914 were censused in 2013 -- the lowest since culling ended in the park in the 1960s. Decreased numbers are attributed to large carnivore recovery (wolf, bears, mountain lion), hunter harvest, and drought-related effects on pregnancy and survival. A total of 4,844 elk were counted in winter 2015 with the expressed hope that the elk decline has stabilized as efforts to maintain wolf numbers have also been implemented (Figure 3).

There is little doubt that the return of gray wolves have altered elk behavior -- group sizes, habitat selection, movements, distribution, and vigilance. There are some indications that elk–wolf interactions are contributing to a release of willows and other woody vegetation on the northern range. At the same time, the debate continues over the overall condition of the Northern Yellowstone range and its carrying capacity, with several range specialists continuing to point out that the range is seriously overstocked by bison and elk.

DISEASE

Many elk and bison in the Greater Yellowstone Ecosystem have been exposed to the bacterium that causes brucellosis. Brucellosis is a contagious bacterial disease that originated in livestock and often causes infected cows (cattle and elk) to abort their first calves. It is transmitted primarily when susceptible animals directly contact infected birth material. No cure exists for brucellosis in wild animals.

Because of their high densities, elk that are fed in winter have sustained high levels of brucellosis. Winter feeding on the Northern Range stopped more than 50 years ago but winter feeding of elk continues at the National Elk Refuge in Jackson, Wyoming, in addition to 22 Wyoming-run feed grounds. The feed grounds were created in the 1900s to maintain Wyoming’s elk herds and limit depredation as migratory routes from summer range to lower elevation winter ranges became blocked by settlement in the Jackson area. Transmission of brucellosis from feed ground elk, where an average of 30% have tested positive for exposure to the bacteria, was the apparent source of infection in Wyoming cattle in 2004.

Elk, deer, and moose in Greater Yellowstone are at moderate risk for exposure to chronic wasting disease (CWD). This fatal infection, transmitted by animal contact or through the environment, has spread to within 130 miles of the park from the southeast.

FALL HUNTING & SPRING SHED HUNTING

The “Welcome Hunter” banners hanging on the front of local taverns, gas stations and restaurants, and the “No Vacancy” signs at local motels in the fall signal the importance of big game hunters, both resident and non-resident, to Idaho, Montana, and Wyoming’s economy. In 2016, big game hunters in Montana spent an estimated $324 million and supported more than 3,300 jobs.

Elk Hunting by State, 2014, State-wide and in the GYE (National Geographic, May 2016)
	Idaho	Montana	Wyoming
Elk Population (state-wide)	105,000	160,000	114,600
Elk Harvested state/GYE	20,600/2,710	25,735/7,310	25,905/10,666
Hunters state/GYE	85,000/12,866	107,663/29,446	58,266/29,957
Elk License Fees*	$43.50/$571.50	$47.00/$860.00	$69.50/$603.50

Includes license, tags, and processing fees for 2016

Shed hunting, the hunting of the cast-off antlers of elk, deer, and moose, has become increasingly popular in recent years, leading to more competition among shed hunters, more conflicts with private land owners from trespass and vandalism, and more impact on big game herds. State Wildlife Management Areas and ranchers are reporting a growing number of incidences. There have even been reported cases where individuals have run antlered elk through trees in early spring in the hope of breaking off antlers.

Currently there are no seasons or required licenses for shed hunting. But that may change as many shed hunters take to the field to gather antlers during the worst time of the year for the animals themselves. Wintering big game animals are very susceptible to any kind of disturbance, especially in the late winter and early spring. At that time of year elk, deer and moose are just trying to hang on until spring green-up, drawing from their diminished body reserves and what little nourishment they can get from surrounding vegetation (like conifer needles and bark). Disturbance from passing motorists, snowmobilers, skiers, dogs, or shed hunters, who intentionally or unintentionally enter areas where elk are bedded down, depletes the little energy the animals have left. This stress and energy depletion leads to sickness and oftentimes death, especially for fawns and calves at this critical time of year.

Ethical shed hunting focuses on not disturbing big game animals on their bedding grounds, respecting public land closures and posted private lands, keeping dogs under control.

Antlers or Horns? Antlers, found on members of the deer family, grow as an extension of the animal’s skull. They are true bone, are a single structure, and, generally, are found only on males. Horns, found on pronghorn, bighorn sheep, and bison, are a two-part structure. An interior portion of bone (an extension of the skull) is covered by an exterior sheath grown by specialized hair follicles (similar to human fingernails). Antlers are shed and regrown yearly while horns are never shed and continue to grow throughout an animal’s life. One exception is the pronghorn, which sheds and regrows its horn sheath each year. Average, healthy, mature bull has 6 tines on each antler: a "six point" or "six by six." One-year-old bulls grow 10–20 inch spikes, sometimes forked. Two-year-old bulls usually have slender antlers with 4 to 5 points. Three-year-old bulls have thicker antlers. Four-year-old and older bulls typically have 6 points; antlers are thicker and longer each year. Eleven- or twelve-year old bulls often grow the heaviest antlers; after that age, the size of antlers generally diminishes.

RESOURCES AND REFERENCES

Yellowstone Elk Information. https://www.nps.gov/yell/learn/nature/elkinfo.htm

On the Path of Yellowstone’s Elk, Nathan Martin. The Atlantic, June 21, 2016.  https://www.theatlantic.com/science/archive/2016/06/on-the-path-of-yellowstones-elk/488063/

Yellowstone Resources and Issues Handbook. U.S. Department of the Interior, pages 200-204.

Yellowstone. National Geographic, May 2016

Elk Facts. Rocky Mountain Elk Foundation. https://elknetwork.com/elkfacts/

Quaking and Trembling

Perhaps no single element so eloquently captures the aesthetic appeal of the Rocky Mountains as the Quaking Aspen (Populus tremuloides). Their white barks with black accents, trembling leaves, and contrasting light green foliage exclaim themselves apart from the dark green of the surrounding pines, firs, and spruces. In the Fall, their presence is further punctuated by the aspen’s vibrant yellow leaves that turn to flecks of gold as the leaves take to the wind.

Aspen stand. Photo by Whitney Tilt

Prime Real Estate. Aspen is the most widely distributed tree species native to North America. In ecological terms, aspen have great “amplitude,” occupying a wide range of elevations, aspects, and soils. Along with riparian areas, aspen communities are considered the most biologically diverse ecosystems in the Intermountain West and critical wildlife habitats. Aspen provide forage for wildlife and livestock and their trunks provide a virtual apartment building for nesting and feeding, especially as they age. The open canopy of aspen stands allows sunlight to reach the forest floor supporting a diverse community of forbs that are also a wildlife magnet. Aspen prefer moist soils and their stands provide cool, shaded habitats. They are particularly adept at retaining water relative to other forest types. As a keystone species, their presence (or absence) significantly affects the survival and abundance of many other closely associated species.

A wide range of bird species, like the Red-naped Sapsucker, depend on aspen for food and nesting sites.
Photo by Mark Resendes.

Heavy Weight Champion of the World. Aspen also have the distinction of being the largest living organism in the known world, by weight. This is a result of aspen’s habitat of propagating primarily vegetatively rather than by seed. Groves of aspen trees are commonly clones, where adult trees are all genetically identical to each and connected by their root system. As adult trees die off, new sprouts, called "suckers", grow from the roots and the clone continues to survive. In some cases, these clones may be tens of thousands of years old. The Pando (Latin for “I spread”) Clone, in Utah’s Fishlake National Forest, is estimated to weight 13 million pounds, cover 106 acres, and have lived for 80,000 years.

Aspen in Decline. The aspen’s valuable contribution to the ecology and esthetics of the region, however, does not ensure its survival. Aspen stands are in significant decline from their historical abundance across the Rockies (Arizona -96%, Colorado -49%, Utah -51%, Wyoming -53%, Montana -64%).

As an early serial species, aspen require open canopies and continuing disturbance events, principally wildfire, windstorms, and/or disease, to maintain stand vigor, stimulate regeneration, and keep the surrounding conifer forest at bay. As aspen stands age and are not renewed by disturbance, conifer species (e.g., Douglas-fir, Engelmann spruce) encroach and overtop the aspen, ultimately crowding the aspen out of existence. Adding to their vulnerability, aspen are a relatively short-lived species (individual trees as opposed to the overall clone) living an average of 60-80 years while their thin, living bark make them susceptible to a host of insect pests and diseases. Add to these vulnerabilities, the fact that they are also tasty, marking young aspen shoots and saplings as a favorite browse for elk and other wildlife, as well as livestock. To add insult to injury, decades of drought and warmer temperatures in the Rocky Mountain West have taken their collective toll.

Managing for Aspen. In the absence of wildfire or wind-throw, several possible treatments are available for managers to improve aspen stand health and vitality. The primary management tools center on creating physical disturbance and managing herbivory.

1. Prescribed fire, wildland fire	Use fire to burn adult trees and encroaching conifers. Found to elicit best aspen regrowth, but comes with risks and liabilities as controlling prescribed fires or allowing wildfires to burn is difficult.
2. Dozing	Mechanically uproot adult trees and break apart root systems. Commonly generates high regeneration of stems, but eliminates adult trees until new growth matures.
3. Cut/Harvest	Cutting adult trees and encroaching conifers allows for more selective harvesting, and is effective at stimulating regrowth, although it may not yield the same kinds of stem densities as treatments 1 or 2.
4. Ripping	Physically breaking up root systems with a ripping blade in the stand. Stimulates regeneration without killing existing adult trees, but generally does not elicit same regeneration responses as methods 1-3.

Successful aspen regeneration at the High Lonesome Ranch, NW Colorado.
Note the remaining decadent stand in the background.

Managing to stimulate aspen regeneration is commonly the first step. In areas of livestock and wildlife use, however, the new growth will need some form of protection from critters. Methods range from herd management to physical barriers:

5. Limit Herbivory

a. Limit or reduce livestock in treatment areas, if possible or practical; not an option for wildlife. b. Erect barriers to fence out wildlife and/or livestock. Erect traditional livestock fencing or other barriers (e.g., jackstrawing felled trees). Fencing can be very effective, but costly and requires continued maintenance.

Aspen in their fall colors. Photo by Whitney Tilt

Resources

Blue Valley Ranch. Aspen Forest Management. http://bluevalleyranch.com/explore/aspen-forest/

Campbell, Robert B. and Dale Bartos. 2001. Aspen Ecosystems: Objectives for Sustaining Biodiversity. USDA Forest Service Proceeding RMRS-P-18.

Paige, Christine. 2017. Bring Back the Gold. 2017. Bugle Magazine, Rocky Mountain Elk Foundation, September-October: 104-112.

Shepperd, Wayne D.; Paul C Rogers; David Burton; and Dale L. Bartos. 2006. Ecology, biodiversity, management, and restoration of aspen in the Sierra Nevada. Gen. Tech. Rep. RMRS-GTR-178. Fort Collins, CO: U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Research Station 122 p.

Season of the Sting

Wandering around the Montana outdoors, whether on foot, horse, or bike is going to bring us into contact with our stinging insect neighbors, specifically bees and wasps. These include the bumblebees, sweat bees, mud-daubers, thread-waisted wasps, honey bees, paper wasps, bald-faced hornets, and yellowjackets. During the late summer and early fall yellowjackets become very active and aggressive in their search for food, increasing the likelihood of us getting stung. At best, such encounters are painful, at worst they can be life-threatening.

Photo: Pest Control Plus: https://www.pestcontrolplus.biz/

yellow-jackets-information/

Wasps and bees, along with ants, are insects in the order Hymenoptera (“membrane wing”). There are literally hundreds of thousands of known and undiscovered Hymenoptera species. Collectively these insects are beneficial pollinators, predators on other insects, and useful scavengers. These insects may be solitary, living and foraging alone without building nests or be social, living together in nests comprising thousands of workers and one queen, organized in a distinct caste system to cooperatively rear young and defend the nest.

The words wasp, hornet and yellowjacket are commonly used interchangeably, but this both confusing and inaccurate. The name “yellowjacket” properly applies to medium-sized black-and-yellow wasp species in the Vespula and Dolichovespula genus, such as the Western Yellowjacket (Vespula pensylvania). “Hornet” is properly applied to larger black-and-ivory species in the Dolichovespula genus, such as the Bald-faced Hornet (Dolichovespula maculate). The other common wasp is the paper wasp, such as the European Paper Wasp (Poliistes dominulus), whose appearance is similar to that of the yellowjacket but slimmer and more elongate. Humans commonly tangle with yellowjackets, hornets, and paper wasps when we inadvertently approach their nest, mistakenly trap them in our clothing, or get between them and their intended food.

Social Insects

The generalized life cycle of social insects is a lesson in evolutionary complexity. In the case of social wasps, young queens emerge from their overwintering sites emerge in the late spring/early summer and begin creating a colony by constructing a new colony. Built for wood fibers chewed from trees, fences, and even cardboard, they construct a small, papery, umbrella-shaped nest underground or in a tree, roof eve, or other site.. Yellowjackets commonly build subterranean nests in abandoned animal burrows, fallen logs, or crevices, while both yellowjackets and bald-faced hornets build aerial nests. After selecting a suitable site, the queen fashions 20 or more hexagon-shaped cells and lays an egg in each. In 2-3 weeks, dependent on temperature, the larva pupates, then emerges as a worker wasp. As their name suggests, these unfertile female “workers” are responsible for finding food, feeding the young, enlarging the nest and defending it. The queen stays in the nest getting fed and laying eggs.

In late summer or early fall, the queen lays a series of unfertilized eggs that grow into drones (fertile males) and fertile females (potential future queens) who remain in the nest, fed by workers until they’re ready to leave the nest in mating flights. Fertile females who have successfully mated with one or more drones overwinter underground or in logs and such to emerge the next year and start the cycle anew. All other members of the colony, including the founding queen, die as winter’s hard freeze arrives.

 Hornets, Yellowjackets, and Paper Wasps

Bald-faced Hornets. Relatively large (3/4”), heavy-bodied, ivory-and-black wasp. Build above-ground paper nests that can be as large as a football. May have leaves and twigs in outer nest wall. Feed on other insects (including yellowjackets) and not commonly a nuisance around human foods. When provoked, their sting is painful due to strength of their venom.

Photo: Bug Hunters Pest Control http://www.bughunterspestcontrol.com/montana-pests.html

Paper Wasps. Similar in overall appearance to yellowjacket but with a slimmer, elongate body, and longer legs that dangle in flight. Build open, down-pointed umbrella-shaped nests with no outer paper covering in protected areas. Feed on soft-bodies, leaf-feeding insects and nectar. Relatively docile but will sting in defense of nest or when found in close contact.

Photo © Derrick Ditchburn/ http://www.dereila.ca/bugs06/page1b.html

Yellowjackets. Medium-sized (1/2” long), black-and-yellow wasp. Nest built above-and below ground, not containing leaves or twigs in outer paper layer. Feed on other insects, carrion, nectar and fruits, and human foods. Most aggressive of the stinging wasps.

Photo: Creative Commons

Uninvited Picnic Guests

Unlike honey bees, yellowjackets do not produce honey or store floral nectar in the nest. They feed primarily on other living insects, killing them by bite or by stinger. As summer progresses, insect prey becomes scarcer, and the nest’s demand for food increases, yellowjackets become more scavengers, seeking out honeydew (the liquid secreted by aphids), fruits, nectar, carrion, and human foods. This scavenging behavior brings yellowjackets into close contact with humans. The incidence humans getting stung increases markedly as the wasps climb on picnic plates and enter open soda cans in search of sugary foods.

While wasps can both bite and sting, it’s the sting we remember. Located at the tip of the abdomen, the sting is a needle-like device that delivers a dose of venom. Only the female worker wasps have stingers, but that is small comfort since they are by far the most numerous and most likely encountered. The stingers of wasps are not barbed (like those of bees), allowing them to sting repeatedly. Wasps sting to kill their insect prey, in defense of their nests, and when otherwise provoked. An interesting evolutionary note is that the sting is a modified egg-laying tube evolved over time into a venom-delivery system. The queen retains the egg-laying ability while the infertile female workers got the sting.

Most of us react to being stung with a string of invectives, moderate-to-intense short-term pain, followed by a localized reaction to the venom consisting of itching, redness and swelling around the sting site. Some 1-3 percent of the human population, however, may experience a systemic (whole-body) reaction that may require emergency medical treatment.

Emergency Medical and First Aid Response

Immediately contact EMS support if the victim:

·         Has known allergic response to insect stings.

·         Cannot breathe easily, tightness in the throat, have difficulty swallowing, feel light-headed.

·         Changes to the skin such as breaking out into hives.

·         Is stung several times, or has been stung in recent days.

·         Is stung inside mouth, or around neck.

First Aid Relief Strategies:

·         Ice compresses to reduce swelling and associated pain.

·         Apply a paste of water and baking soda to sting site.

·         Use vinegar or anti-itch cream to treat itching,

·         Take OTC oral antihistamines and pain medicines.

·         Gently wash sting site with soap and warm water.

Resources

Homeowner Guide to Yellowjackets, Bald-Faced Hornets and Paper Wasps. Edward Bechinski, Frank Merickel, Lyndsie Stoltman, and Hugh Homan. University of Idaho Extension, Bulletin 852. http://extension.uidaho.edu/clearwater/files/2014/11/Homeowner-Guide-to-Yellowjackets-Bald-Faced-Hornets-and-Paper-Wasps.pdf

Montana Bee Identification Guide. Casey Delphia, Kevin O’Neill, and Scott Prajzner. Montana State University. http://www.pollinator.org/PDFs/MontanaBeeGuide-Final.pdf

Social wasps and Bees in the Upper Midwest. Jeff Hahn, Laura Jesse and Patrick Liesch. University of Minnesota Extension. https://www.extension.umn.edu/garden/insects/find/wasp-and-bee-control/

What to Do for Yellow Jacket Stings. Healthline.com @ http://www.healthline.com/health/yellow-jacket-stings#overview1

Fire and Ice - Paradise Valley Geology 101

 John Gillespie & Whitney Tilt

First Fire

Strata volcanoes erupted frequently 65-35 million years ago in Paleocene through Eocene times (Figure 1), leaving deposits of andesitic lava, lahar debris flows and petrified forests – forming the mountains of the Absaroka Volcanic Supergroup.  These volcanoes, part of a “ring of fire”, were caused by the subduction of the Pacific Plate under the North American Plate and a contemporaneous uplift called the Laramide Orogeny. Two northwest trending belts of eruptive centers, termed the Eastern Absaroka Belt and the Western Absaroka Belt, include well known peaks like Sunlight, Washburn, Electric, Emigrant and Hyalite.  The ancestral Yellowstone River drained the mountainous topography. Paradise Valley formed around during this time. 

35-25 million years ago during the Oligocene epoch the valley filled with sediments from the eroding mountains and the valley collected the fluvial deposits of the Renova Formation – much of which is now eroded.  

From 25 to 8 million years ago during Miocene epoch tuffaceous siltstones like those at Hepburn’s Mesa were deposited in shallow alkaline lakes and mudflats much like those seen at the Salton Sea today.   

First Hints of More Fire

Much of the volcanic ash within Hepburn’s Mesa siltstone originates from volcanic eruptions tied to the first arrival of the North American Plate over the mantle hot spot that dominates the active volcano at Yellowstone today. The track of the heat is along the Snake River Plain where the sheet-like edge of the North American Plate moves to the west-southwest at an inch or two a year over the relatively stationary propane torch of the hot spot, allowing super-heated magma to penetrate through the crust along its route. The 16.5 million year old white tuffaceous siltstone at Hepburn’s Mesa coincides with air-fall ash from the first eruption of the hot spot – the McDermitt caldera, which occurred soon after the deposition of the Columbia flood basalts in Washington State. The McDermitt ash-fall caused the death and preservation of a rich assemblage of Miocene mammal life at Hepburn Mesa – including Merychippus – the first equine to exhibit the head of today’s horses. Another of these ash-falls, tied to the Bruneau-Jarbridge caldera, ~12 million years ago, resulted in similar death and preservation at Ashfall Fossil Beds State Park in Nebraska where excellently preserved Teleoceras, a hippo-like ancestor of the rhinoceros, are stacked in layers of ash-rich siltstone.

Coming after the Miocene lakes the Yellowstone River dominates the return from lacustrine deposition to fluvial deposition.  At Hepburn’s Mesa and at many places in Paradise valley, a coarsely-sorted, mixed-grain, mixed-color conglomerate, deposited in the river bottom, can be observed immediately above white tuffaceous siltstone.

Red Hot Fire: Arrival of Yellowstone over the Mantle Hot Spot

2.2 million years ago, the waters of the Yellowstone River had formidable competition.  A lava flow, a precursor to the Huckleberry Ridge super eruption –one of the most cataclysmic volcanic eruptions in history, gravitated to the topographic low occupied by the river.  In a boiling battle with sound and light, hiss and sizzle beyond comprehension like can be seen where lava from Pu’u  O’o meets the ocean at Kilauea today, the lava bested the water as is documented by the thick black deposition of basalt that lies immediately above the river bed conglomerate.  The basalt originates from a local vent and can be traced down flow to a site where it pinches out just north of Emigrant.  The 2.2 million year radiometric age of this basalt matches that of Junction Butte in the national park, predating the 2.1 million year Huckleberry Ridge super eruption by 100,000 years.  Incongruently, there are glacial striations scratching the top of the basalt and a thin profile of sediment above the basalt is glacial till with glacial erratic boulders – hints of the ice that followed the fire.

Figure 1. History of the Yellowstone Hotspot – creating the Snake River Plain

A Geological Collision

Paradise Valley lies between the Great Plains and the edge of the Yellowstone volcanic plateau. According to the Montana-Yellowstone Geologic Field Guide Database, the valley shares basement rocks with the continental interior; Paleozoic and Mesozoic lithologies with the western interior, compressive tectonics with the Fold and Thrust Belt to the west; Basin and Range with the west and south; and Cenozoic volcanism with much of the surrounding region. The database describes the area as a “microcosm of the evolution of the geological understanding of the American West.”

While you may or may not understand the above, overly-technical description, here is a partial list of some of the geological highlights in the Paradise Valley. All are easily found and observed:

•         Landforms: Gallatin Range, Beartooth Range, Hepburn Mesa, Yankee Jim Canyon
•         Metamorphic basement rocks of the North Snowy Block, near Pine Creek
•         Paleozoic, Mesozoic, and Cenozoic sedimentary rocks
•         Hepburn’s Mesa Formation basalts
•         Point of Rocks volcanic/intrusive center (Absaroka Volcanic Field)
•         Travertine deposits at Gardiner and the Liberty Cap at Mammoth
•         Glacial deposits (Wisconsinan/Pinedale age) – more below
•         Devils Slide (Figure 2)
•         Giant Ripples flood deposits at Corwin Springs
•         Rangefront alluvial fans
•         Chico and La Duke Hot Springs hydrothermal features
•         Nelson and Armstrong Spring Creeks

Mountain Formation

Beginning some 65 million years ago, during the early Cenozoic, the Yellowstone region underwent periods of uplift and folding that alternated with periods of quiet and erosion. Volcanic activity, accompanied by uplift and folding, showered the landscape with volcanic ash, dust, silt and sand. Deluges of coarser debris flowed down the volcano flanks in lahars which became the volcanic breccias. Periods of quiet allowed semi-tropical plants and animals to flourish and nearly 200 fossil species have been identified in the Absarokas, perhaps the most diverse petrified forest in the world.  These include unexpected species like breadfruit, persimmon, magnolia and mangrove.  Resumed volcanism buried or transported entire forests into valleys as witnessed at Spirit Lake below Mount St. Helens and other places around the globe.

The Beartooth Plateau, forming the eastern boundary of Paradise Valley and consisting mainly of Precambrian basement rocks with a local veneer of Eocene Absaroka volcanic rocks, pushed its way upward through sedimentary rock during the Laramide orogeny (~70-45 million years ago).  It contains some of the oldest exposed rock on Earth. The Quad Creek Quartzite on Beartooth Pass has been radiometrically dated as 3.95 billion years old. Yankee Jim Canyon provides exposures of foliated crystalline metamorphic rock - granitic gneiss, micaceous schist, and pegmatite dikes formed miles below the surface.

Cinnabar Mountain, home to the Triassic Chugwater red bed of the Devil’s Slide, provides a view of remnants of the hanging wall of the Gardiner thrust fault exposing nearly vertical beds of Paleozoic and Mesozoic rock (Figure 2) and provides “hieroglyph-like” evidence of ~500 million years of Earth history.

The Gallatin Range, forming the western boundary of Paradise Valley, is generally lower in elevation and less vertical as compared to the Beartooths.  Now at ~10,000 elevation, many of the peaks are comprised of Paleozoic carbonates that were originally deposited in epieric oceans.   Paradise Valley is in a downthrown position relative to the Beartooths as a result of Basin & Range normal faulting that arrived about the same time as the Yellowstone Hot Spot and they were buried by younger volcanic rock after faulting occurred.  Paradise Valley is the easternmost expression of the Basin and Range province. The extensional tectonics, often described as a rift, are represented by the presence of scarps along the Deep Creek-Luccock Park-Emigrant fault.

As uplift continued across the region, the mountains and valleys grew in elevation and cooled. Increasing snowfall failed to melt as rapidly as it fell. The Ice Ages arrived.  

Figure 2. Devils Slide, Corwin Springs. Vertical bands with older (Paleozoic) rocks on right and younger (Mesozoic) rocks on left.  1- Pinedale glacial till; 2-Devonian-Mississippian undifferentiated limestone; 3-Triassic rock; 4-Cretaceous undifferentiated rock.

Ice Age Cometh

Beginning about two and a half million years ago, yesterday in geologic time, the Pleistocene epoch in the northern hemisphere has been characterized marked by advances and retreats of continental ice sheets. The Yellowstone region underwent a series of glacial stages. The earliest glaciations were largely bulldozed away by subsequent ones, removing evidence of their distribution.

The Bull Lake glaciation, ~200,000 years ago through 130,000 years ago, concurrent with the continental Illinois glaciation, created widespread valley glaciers including one that covered the northwest portion of Yellowstone Park, and flowed northward down the current course of the Yellowstone River. Overtopping lesser peaks like Cinnabar and Dome Mountain as it flowed northward, its width varied from 3-6 miles and it height estimated at 3,000 feet. Most of the landforms created by the Bull Lake glaciation are gouged and overprinted by the subsequent Pindale glaciation, but some good landforms are preserved in the Teton and West Yellowstone areas.

The region’s last glaciation, the Pinedale, occurred concurrent with continental Wisconsin glaciation began approximately 70,000 years ago and reached its maximum ~25,000 years ago.  It left the most visible record and its recession has been carefully studied by cosmogenic and other dating methods. The Beartooth Mountains, capturing precipitation from the caldera-rich lowland of the Snake River Plain, provided the incubator for the Yellowstone Outlet Glacier. From its source high in the Beartooths near Granite Peak to its terminus at the Eight Mile Moraine near the junction of the Yellowstone River and Mill Creek, it was nearly 70 miles long.   Based on eroded mountain tops and remnant horns and aretes, in some places towards its center the glacier was approximately 4,000’ thick. Tom Miner and Big Creek were both covered by Pinedale ice. Evidence of this glaciation can be seen in moraine remnants around Chico Hot Springs and the ice- margin channels and terraces on the mountain slopes between Big Creek and Fridley Creek on the west side of the valley. As the glacier receeded, much like the collapse of Glacial Lake MIssoula, ice dams broke in the Lamar Valley and catastrophically released massive volumes of impounded water. Enormous floods, some with headwalls estimated at 150-300’, ripped down the Black Canyon of the Yellowstone and deposited ripple marked flood bars of boulders as much as 50’ high near Gardiner.

Glacial ice left its signature on the Paradise Valley landscape in the form of moraines, glacial striations, moraines, ice marginal channels, kettles, polished sheepback hills, till and glacial erratics, including many along Big Creek.

In the blink of an eye (geologically speaking), plants and animals recolonized the landscape and humans arrived to hunt and forage the abundance of life at the ice edge. Along with sheep traps and bison jumps, lithic quarries, stone circles, fire pits and other artifacts of Clovis and other Paleo-Indian peoples are found in the area.

Hepburn’s Mesa

A glimpse of the geological history of the valley is on view at Hepburn’s Mesa (Figure 3), the bluffs dominating the east side of the Yellowstone River, opposite Mountain Sky Guest Ranch lands. At the bottom are the oldest rocks-light colored fine-grained sedimentary rocks formed from sediments deposited in an ancient lake that once occupied the site. Atop these rocks are the unconsolidated river bed gravels and conglomerates that are in turn capped by a basaltic lava flow, and lastly by glacial till. 

Figure 3. Aerial photo of Yellowstone River and Big Creek drainage, looking south. 1-Hepburn's Mesa; 2-Confluence of Big Creek & Yellowstone River; 3-Glacial till; 4-Sheep Rock; 5- Mountain Sky Guest Ranch.

The sedimentary beds contain abundant Miocene fossils, including ancient rodents, moles, and a proto-horse called Merychippus. The basalt lava flow erupted from a volcanic vent some 2.2 million years ago. It is of the same age as the Junction Butte basalt in Yellowstone Park and is a precursor lava flow to the Huckleberry Ridge super eruption at Yellowstone.  Its dark coloring is the result of high concentration of iron, including magnetite. On top of the mesa lies the youngest material, glacial till dating to the Pleistocene age. The surface of these deposits is hummocky and is littered with abundant glacial erratic boulders. For generations, Native Americans drove bison off the mesa’s cliffs and captured sheep in rock traps.

Hepburn’s Mesa is named for John Hepburn, a local rancher, rockhound and amateur paleontologist. He arrived in the Emigrant area in 1909 after working in Yellowstone National Park for many years. From 1935 until his death in 1959, he operated a museum displaying many of the geologic specimens and fossils he had found in this area. The museum still stands and is listed on the National Register of Historic Places.

Fire & Ice Talk

Fire (Volcanics). Volcanic activity arises from the Earth’s mantle as magma pushes its way up through fissures and other fractures in the overlying rock forming dikes, sills, caps, and flows. Sheep Rock is a volcanic dike – a vertical shaft of igneous rock (dacite) that has become exposed as the softer surrounding rock has weathered away. There are several types of volcanic rock including basalt, andesite, dacite, and rhyolite. Basalt and andesite are dark colored and fine-grained while dacite is quartz-rich and generally lighter in color. Rhyolite is silica rich and light-colored and it the “Yellowstone.” 

Glaciers are great rivers of ice formed by the accumulation and compaction of snow on mountains. During their residency in the region they sculpted mountains and carved out valleys. For thousands of years, snowfall accumulated and fed the river of ice as it flowed downslope from the mountain tops. Glaciers are frozen conveyor belts that take part of the surrounding land with it as it moves downslope. Rocks became entrained in its ice. As the ice moved, these rocks scoured away more of the underlying surface. Where the glacier’s forward-most process stopped, it discharged its melt water, dropped its rocks, and staged a series of retreats.

Looking across the Paradise Valley an irregular topography is evident including a series of hummocky hills, some shaped as linear ridges, some as flat-topped headlands above the Yellowstone River, and some as a series of gently rolling hills. These moraines and outwashes are the remnants of long-gone glaciers.

The landform of present-day Paradise Valley is the result of several large glaciers that flowed down the valley, from south to north, leaving a landscape shaped by moraines and outwash. The glaciers may be gone, but their influence is plain to see today.

Moraines are composed of glacial till, an unsorted mixture of silt, sand, pebbles, and boulders dumped directly from the glacial ice. Ground moraines accumulated as irregular blanket of till deposited under the glacier while terminal, recessional, and lateral moraines formed as retreating glaciers left a series of “windrows” at the terminus of the glacier, and alongside the ice mass. Collectively these moraines record the glacial record. In the Paradise Valley, terminal moraines are evident at the outlet of Pine Creek and most of the other creeks flowing from the Absaroka Mountains. Just south of Pine Creek on Highway 89, the road climbs up and over the terminal moraine of the Pinedale Glacial Stage, which reached its maximum northward extent some 16,500 years ago. To the south, the rolling hills area evidence of the ground moraine that covers the entire valley floor. The larger cross-valley ridges formed in front of the retreating glaciers while the lateral moraines formed alongside the ice forms. A definitive characteristic of a moraine is that its till is unsorted – sediment of all different sizes is found jumbled together with no layers evident. This characteristic helps distinguish materials deposited by glaciers from those deposited by running water which tends to deposit different sizes of rocks in different areas. Since the end of the last ice age, some 10,000 years ago, soil has developed on the moraines and trees have taken root.

Outwash is well sorted sand and gravel deposits delivered by the meltwater flowing from the end of the glacier. Outwash deposits are flat on top as compared to the hummocks of the moraines. Imagine 3,000 feet of ice on top of you. As the glacier flowed, its sheer weight ground the underlying rock surface and carried the debris along. The meltwater emerging from the foot of the glacier deposited its load of sediment over the outwash plain, with larger boulders being deposited near the moraines, and smaller particles travelling further downstream before being deposited. On either side of the Yellowstone there are prominent, tall, flat-topped benches formed by the outwash from the last glaciation. Over more recent time, the river has cut its course down through these sediments.

Figure 5. Pine Creek Drainage in background; Pine Creek terminal moraine in mid-ground, and Yellowstone River in foreground. Picture taken looking ENE from Mallard’s Rest Fish Access Site.

Sources and Resources

Berg, Richard B., Jeffrey D Lonn, and William W. Locke. 1999. Geological Map of the Gardiner 30’ x 60’ Quadrangle, South-Central Montana. Montana Bureau of Mines and Geology.

Fritz, William J. and Thomas, Robert C. 2011. Roadside Geology of the Yellowstone Country, Second Edition Missoula: Mountain Press Publishing Company. 149 pp.

Illustrated Glossary of Alpine Glacial Landforms.  https://www4.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary/index.html

Montana-Yellowstone Geologic Field Guide Database. http://serc.carleton.edu/research_education/mtroadlogs/logs/NWGeol-1995-SWMT-1.html

U.S. Department of the Interior. National Register of Historic Places Registration Form for the John Hepburn Place, September 5, 2005.