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HISTORY

 The Corp of Discovery led by Lewis and Clark were the first whites to explore the greater Yellowstone region among them was one of the most celebrated hunter and woodsman of that period, John Colter. On the return of the expedition in 1908, Colter returned to the Yellowstone and trapped this region and in doing so became the first white visitor to what is now Yellowstone National Park. Upon his return, his "tales" were so unbelievable that no author or mapmaker would publish it for fear of scrutiny amongst their peers.

Colter’s stories about the wonders and wildlife, led the fur traders to explore the Yellowstone regions. Most of the mountain men during that era were experienced in trapping and survival, they were also illiterate. Fortunately, Osborn Russell was unique, he knew how to trap, read and write and his journals are the earliest accounts of the Yellowstone region.

 

"There is something in the wild scenery of this valley which I cannot describe: but the impressions made upon my mind while gazing from a high eminence on the surrounding landscape one evening as the sun was gently gliding behind the western mountain and casting its gigantic shadows across the vale were such as time can never efface. For my own part I almost wished I could spend the remainder of my days in a place like this where happiness and contentment seemed to reign in wild romantic splendor" - Lamar Valley, Osborne Russell 1835

"I sat there in amazement, while my companions came up, and after that, it seemed to me it was 5 minutes before anyone spoke. Language is inadequate to convey a just conception of the grandeur and sublimity of this masterpiece of nature's handiwork" Artist Point - Charles Cook 1869

In the latter part of 1840 the fur trade was coming to an end. The trappers who remained in the region adapted and among them was the distinguished, Jim Bridger. Bridger, a natural born topographer, new the fur trade was over and became a guide, scout and legendary story teller. His knowledge of what is now Yellowstone National Park was unparalleled and he became the first "geographer" of the region and was summoned to guide Capt. W.F Raynolds including Dr. Ferdinand Hayden and the Raynold's Expedition of 1859. Due to the expeditions schedule and uncompromising weather this first organized exploration of the Yellowstone region was unsuccessful.

During the 1850's to 1870, miners inhabited the Yellowstone and in doing so helped to publicize the region however with not much more credibility than their trapper predecessors. In 1863, Walter Delacy and his party set out to prospect through the Yellowstone. Although the party was equipped with prospector tools and no survey equipment, his party made many new discoveries including Shoshone and Lewis Lake he also published the first map of the Yellowstone area. By 1870, gold fever was gone and the great Yellowstone expeditions began.

In 1869, D.E. Folsom, William Peterson and C.W. Cook completed the first successful privately organized Yellowstone expedition. After 36 days, they completed their quest and returned back to Helena, Montana to publish their findings only at first to receive the same response as John Colter and Jim Bridger, that their story was too risky. Eventually their exploits were published by the Western Monthly Magazine of Chicago.

One year after the Folsom-Cook party reported about the wonders of Yellowstone, Gen. Henry D. Washburn organized the next expedition into Yellowstone. His party included Nathaniel P Langford and a military escort led by Gustavus C..Doane. This Party was responsible in the early place names of Yellowstone National Park's most historical sites including Old Faithful, Castle Geyser, Giant Geyser and Grand Canyon of the Yellowstone. This was a successful expedition in terms of their credibility in verifying and naming early historic landmarks. The mission was not without hardship when one of the party members, Truman C. Everts became lost and endured a 37 day ordeal to finally be rescued by Jack Baronett. Upon the return of the Washburn-Langford-Doane Expedition, the leaders of the party set out in their own specific ways by lectures and print (no www.YellowstoneNationlPark.com back then). During one of Langford's lectures. Dr. Ferdinand Hayden was in attendance.

Hayden proceeded to capitalize on the current interest in the Yellowstone region by asking Congress for funds for an official expedition into the Yellowstone region. With influential friends seated in Congress at that time, it did not take long before he was granted appropriations for $40,000 for a geographical survey to investigate the Missouri and Yellowstone territories. Hayden assembled his dream team including James Stevenson, Albert Peale, William Jackson and Thomas Moran. The artists and photographer proved to be invaluable to the expedition for their paintings and photographs served as dramatic and effective testimonials in favor of establishing the park. Along with new discoveries and place names the party collected geological, botanical, zoological specimens, sketches, photographs and countless volumes of exploration notes. This collection of data was brought before the public and congress. The bill's chief supporters convinced their colleagues that the region's real value was as a park area, to be preserved in its natural state. On March 1, President Grant signed the bill into law, establishing the Yellowstone region as a public park and setting a major conservation precedent. The Nation had its first national park; an area of exceptional beauty was set aside for the enjoyment of generations to come, and a tradition of preserving similar areas was established.

Yellowstone Lake: Where Fire Meets Ice

Compared to Old Faithful, Yellowstone Lake seems fairly dull, but appearances can be deceiving. The bottom of Yellowstone Lake is hydrothermally active, and scientists are studying hydrothermal vents, spires, craters, domes, rhyolitic lava flows and other evidence of glacial, tectonic and sedimentation processes that created the Yellowstone Lake of today.

While millions of visitors view Old Faithful and the surface of Yellowstone Lake every year, only a handful of scientists and technicians know the bottom of the lake, among them Lisa Morgan, Ph.D., with the U.S. Geological Survey (USGS). Using multi-beam sonar mapping and seismic surveys, as well as a submersible craft, Morgan and her colleagues are gaining fresh insights into the geologic forces that are shaping this high-altitude lake that straddles the southeast margin of the 30- by 45-mile Yellowstone Caldera.

The caldera is the collapsed remains of a super volcano that erupted 640,000 years ago. Below the caldera is an underlying magma body that releases tremendous heat - the source of Yellowstone's hydrothermal features.

Generally, in Yellowstone Lake, lava flows lie within the caldera margin and have a thin veneer of glacial debris.

"This is where fire met ice," said Morgan.

Morgan helped map Yellowstone Lake from 1999 to 2003. The first time the lake was surveyed was the Hayden Survey in 1871, a 24-day effort that gathered 300 depth readings, or data points. Morgan's map project took four summers and generated 240 million data points, providing a much more detailed map that contains mountains of data yet to be fully analyzed.

Discoveries

In 1999, Morgan's research revealed a dome - the size of seven football fields - on the bottom of the lake. That got people excited for a while, amid fears of a hydrothermal explosion that made the CBS Evening News in 2004. No explosion yet, and no changes in the chemistry of hot waters that emerge from the north basin hydrothermal dome.

"A significant change, such as CO2 [carbon dioxide concentrations], might tell us something," said Morgan.

Her most recent research finds that the rhyolitic lava flows across the bottom of the lake help direct the flow of hydrothermal fluids underneath. The hydrothermal fluids either find their way to the edges of the lava flows or move upward through fractured, permeable zones.

About 200,000 years ago, said Morgan, post-caldera rhyolitic lava flows began moving into the lake-park-wide there were about 35 events. "We can see the record of that activity in the lake. It is a very big find. Prior to our recent mapping, no one had ever suggested lava flows in the lake."

Morgan theorizes that hydrothermal fluids come up along deep fractures through sediments, hit the base of the overlying lava flows, divert laterally and come up along edges of the lava flows. Fractures caused by inflation and deflation of the caldera also play a role.

Another discovery emerged from observations in late September 2002, when researchers were boating above the north basin hydrothermal field. Morgan said there was a strong scent of rotten eggs in the air, as well as rising bubbles from the bottom and a plume of fine sediments. These events weren't noticed in early summer but were noticed in late summer and early fall in subsequent years.

"We attributed this with a drop in lake level in late summer and early fall," said Morgan. Apparently, water levels and water pressure declined enough to increase flow rates from active hydrothermal vent systems.

This actually ties in with what other scientists have observed in the Norris Geyser Basin - a "fall disturbance" that produces sudden changes in thermal springs, temperatures and water chemistry. That fall disturbance is likely due to a slight but critical drop in the water table of Norris Basin.

Boom!

Morgan is also studying large hydrothermal explosion craters in and around Yellowstone Lake. Unlike volcanic explosions characterized by super-heated pyroclastic flows (hot gas, ash, rock and lava), hydrothermal explosions result from magma-heated water and steam building pressure underground. If pressure can be released by geysers or hot springs, nothing happens. But if the pressure builds up too far, the results can range from a hearty burp to a deadly explosion of steam and shattered rock.

Explosions can result in pits or craters that range in size from a few yards to hundreds of yards, tossing debris miles away.

The last really big hydrothermal explosions were 3,000 and 14,000 years ago, based on radiocarbon dating of wood fragments found in the debris. The largest hydrothermal explosion crater is Mary's Bay, said Morgan. Since 1872, there have been 20 minor blowouts. In 1989, the Pork Chop Geyser in Norris Basin got clogged. When the pressure broke loose, rocks rained around tourists some 200 yards away.

Sites around Yellowstone Lake that were formed by hydrothermal explosions include Indian Ponds, Evil Twin over in West Thumb and Duck Lake - a crater on the edge of West Thumb Geyser Basin.

"These are relatively shallow systems," said Morgan. "In Yellowstone, there's no evidence for a volcanic eruption triggering a hydrothermal eruption and vice versa. Heat from the magma chamber (4 to 5 miles below) is providing the energy for heating the water in the hydrothermal systems."

Big, powerful and deadly hydrothermal explosions are rare, said Morgan, but are more frequent than volcanic eruptions in Yellowstone.

A powerful earthquake and a big landslide could displace enough water in Yellowstone Lake to uncork a hydrothermal explosion, said Morgan. "We know we have lots of landslide deposits along the shores of the lake," said Morgan. "We don't know if there was just one or a series of landslides. It makes a big difference in understanding hazards associated with the lake."

Bugs 'n' stuff

Morgan has also found time to work with microbiologists, taking the remotely operated submersible down to collect bacteria mats growing around hydrothermal vents.

"There's about 200,000 years of history locked up in the sediment of Lake Yellowstone," said Morgan. Sediment could tell Morgan what was happening locally, or even provide perspective on volcanic activity in the Cascade Range, by looking at ash deposits. Biologists could look at the pollen in the lake's sediment, she added.

Morgan is finishing a map of the lake this summer, showing the geologic forces contributing to shaping the current lake, from fire to ice. She's also working on a history of Yellowstone Lake, including a map of large hydrothermal explosions - most of which should be posted on a USGS web site by next fall.

Should research appropriations increase, Morgan would like to work more on the seismic data she's accumulated, and possibly start a coring program collecting cores at selected sites in Yellowstone Lake.

Brodie Farquhar is a writer living in Lander, Wyoming. He is the contributing editor of Yellowstone Journal.

Geology: Calderas

Just a few years after Boyd's paper appeared, the U.S. Geological Survey mounted an extensive investigation of Yellowstone's geology, assigning some of its brightest young scientists to the task. Among them was Bob Christiansen, who studied the young ash flow tuffs in great detail. What follows is based on his research and that of his co-workers, including geologists, chemists, and geophysicists, some of whom continue their studies of Yellowstone today.

Christiansen and his team recognized that not one but two welded tuffs rimmed the plateaulava flows; one was 2.1 million years old (Huckleberry Ridge Tuff ) and the younger 0.65 million years (Lava Creek Tuff ). A third tuff, to the west in Idaho, was 1.3 million years old (Mesa Falls Tuff). Together they form the Yellowstone Group of tuffs.

These tuffs demonstrated conclusively that the volcanic events forming Yellowstone were not the products of many million years of geologic change ending many millions of years ago. Rather, their time scale was compressed into only the last two million years. A long geologic history would have allowed a more leisurely progression of events—a lava flow here, then a million years later another flow there. A longer geologic history would also have called for intermittent periods of magma (molten rock) formation separated by periods of volcanic quiescence. Instead, this short time scale compressed the sequence of explosions and flows and required a heat source much larger and younger than ever before imagined.

Calderas are large basin-shaped volcanic depressions more or less circular in form. Caldera eruptions on the Yellowstone scale have a worldwide frequency of perhaps once every hundred thousand years. Somewhat smaller eruptions, on the scale of Crater Lake-Mount Mazama in Oregon, are more frequent, perhaps every 1,000 years or less. Such explosive eruptions were not isolated events. Rather, they were climactic stages of magmatic processes that extended over hundreds of thousands of years.

No one has ever seen a volcanic explosion on the scale of the Yellowstone eruptions, but smaller explosions have been observed and their activity described. Consider Mount Tambora, on the island of Sumbawa, Indonesia to grasp some idea of what's involved when a caldera forms during or just after an ash flow eruption. For about three years the volcano rumbled and fumed before a moderate eruption on April 5, 1815 produced thundering explosions heard 870 miles away. Next morning volcanic ash began to fall and continued to fall though the explosions became progressively weaker,

On the evening of April 10 the mountain went wild. Eye witnesses 20 miles away described three columns of flame rising from the crater and combining into one at a great height. The whole mountain seemed to be covered with flowing liquid fire. Soon these distant viewers were pelted with 8-inch pumice stones hurled from the volcano. Clouds of ash, borne by violent gaseous currents, blasted through nearby towns blowing away houses and uprooting trees. The village of Tambora was destroyed by rolling masses of incandescent, hot ash.

On April 16, booming explosions loud enough to be heard on Sumatra, 1600 miles to the west, continued into evening. Mount Tambora, still covered with clouds higher up, seemed to be flaming on its lower slopes. For a day or two, skies turned jet black and the air cold. When the eruption ended, the ash cloud drifted west and settled on all islands downwind. With the expulsion of so much magma, the mountain collapsed, unsupported from within, forming a great caldera. Lombok, 124 miles to the west, was covered by a blanket of ash two feet thick. Tidal waves crashed on islands hundreds of miles away. Waves and ash falls killed more than 88,000 people.

Ash blasted into the stratosphere circled the earth several times causing unusually beautiful sunsets in London early that summer. In 1816, mean temperatures in the northern hemisphere dropped by half to more than 1° E Farmers in Europe and America called this the year without a summer.

Tambora's eruption was the largest and deadliest volcanic event in recorded history. How does it compare with the Yellowstone caldera eruptions? If we reduce all the ash from Tambora to dense rock equivalents and include all ash flow tuffs that formed at the same time, we come up with about 36 cubic miles of rock. Quite a bit compared with the destructive U.S. eruptions of Mount St. Helens in 1980 that produced about 1/4 cubic mile.

Both of these shrink to insignificance when compared with Yellowstone. The volume of volcanic rock produced by the first Yellowstone caldera eruption was about 600 cubic miles—about 17 times more than Tambora, and 2,400 times as much as Mount St. Helen's, an almost incomprehensible figure. One more statistic: Ash from Tambora drifted downwind more than 800 miles; Yellowstone ash is found in Ventura, California to the west and the Iowa to the east. It is likely the earth has seldom in its long history experienced caldera explosions on the scale of those that created Yellowstone.

Three gigantic caldera eruptions rocked the Greater Yellowstone Ecosystem. The first and largest, Huckleberry Ridge caldera, blew up about 2.1 million years ago. Its center was in western Yellowstone National Park, but it extended into Island Park, Idaho. Welded tuff from this cycle is called the Huckleberry Ridge Tuff. The yellow rocks along the road in Golden Gate between Mammoth Hot Springs and Swan Lake Flats are Huckleberry Ridge Tuff. So are the tuffs that hold up much of Signal Mountain in Grand Teton National Park, and that crop out along the west side of the Teton Range, in Idaho.

The second great explosion formed the Island Park caldera 1.3 million years ago. This caldera, the smallest of the three, lies just west of Yellowstone in Idaho, within the western part of the Huckleberry Ridge caldera.

The youngest caldera, Lava Creek, erupted the Lava Creek Tuff, 0.65 million years old. It overlaps the Huckleberry Ridge caldera, but its eastern margin is about 10 miles farther east. Because it is the youngest, its tuffs and associated lava flows are best exposed and its history best known. Its eruption may have destroyed the south part of the Washburn Range.

Although the Lava Creek Tuff is 0.65 million years old, its caldera began to evolve about 1.2 million years ago when rhyolite lavas flowed intermittently onto the surface of the Yellowstone Plateau from slowly forming, crescentic fractures. Over a period of 600,000 years these ring fractures grew and coalesced to form a system of fractures enclosing the part of the plateau that later collapsed into the Lava Creek caldera.

The ring fractures were a surface expression of a huge body of magma or molten rock, forming in upper levels of the earth's crust. As the magma chamber grew in volume, it stretched and bulged the crust above it. The upper crust was rigid and brittle; it fractured more easily than it bent; thus fractures, or faults, developed around the bulge. As the bulge rose higher, the ring fractures propagated downward toward the magma chamber.

In the magma chamber itself, the molten material was evolving chemically. Less dense materials were concentrating in the upper part of the chamber, including the more silica-rich magma, various gases, and water. Then, with maximum segregation in the magma chamber, volatiles concentrating in its upper part, and ring fractures propagating downward, the gun was loaded and ****ed. What actually triggered the caldera-forming explosions is hard to say, but the pressures in the magma chamber must have exceeded the gravitational pressures of the overlying rocks.

Imagine a bottle of carbonated water lying in the sun. Pick it up, shake it vigorously, maybe tap the cap...boom, it blows off. Instantly the pressure in the bottle drops, the dissolved carbon dioxide exsolves into bubbles and an expanding mass of bubbles and water jets into the sky. In a few seconds, the event is over. Wipe off your face and check the bottle; some of the water remains, but most of the gas is gone. This simple scenario is a scaled-down analogy of what happened 600,000 years ago in Yellowstone when the volatile-rich upper part of the magma chamber vented and erupted the Lava Creek Tuff. The exolv-ing gas expanded in the magma, making a much larger volume of frothy fluid. This expanding, low-density hot gas and magma mixture rose rapidly. It vented at the surface as a sustained explosion of white-hot froth. A scene from the depths of Dante's Inferno.

Driven by hot vapors, giant fountains of incandescent ash at temperatures near 1,800° F burst from the ring fractures. Plumes of ash jetted into the stratosphere where planetary winds carried it around the world blanketing tens of thousands of square miles with thin coverlets of volcanic dust. Nearer the vents, fiery clouds of dense ash, fluidized by the expanding gas, boiled over crater rims and rushed across the countryside at speeds over one hundred miles per hour, vaporizing forests, animals, birds, and streams into varicolored puffs of steam. Gaping ring fractures extended downward into the magma chamber providing conduits for continuing foaming ash flows.

More and more vapor-driven ash poured from the ring fractures, creating a crescendo of fury. As the magma chamber emptied, large sections of the foundering magma chamber roof collapsed along the ring fractures, triggering a chain reaction that produced a caldera 45 miles long and 28 miles wide.

Hot ash flows are fascinating. Driven by expanding gas, they are really clouds of hot glass shards and pumice plus expanding gas whose turbulence keeps everything flowing like water. But as the gas escapes, the viscosity increases, motion ceases, and the ash settles into a layer more than one hundred feet thick. This deposit is still extremely hot, and as it compresses under its own weight, the sticky glass shards fuse into a welded tuff. The upper part of the ash cools too rapidly to weld and is either unconsolidated or weakly cemented by vapors of escaping gas.

The engine of destruction didn't take long to run down, just a few hours or, at most, a few days. Hours? Days? Yes, incredible as it may seem. Evidence for the astonishing rapidity of this eruption is found in detailed study of the tuff. Eruptions that are separated by any significant period of time have discernible boundary effects that clearly separate one tuff from another. Runoff water, for example, would erode small channels in the surface of a flow or the chilled tops of separate flows would mark the emplacements of separate cooling units. No evidence exists to suggest such a cooling history in Yellowstone. Rather, the caldera venting appears to have developed in two separate parts of the magma chamber simultaneously and been continuous over a very short time. In a period of time reasonably inferred to be hours, more than 240 cubic miles of Lava Creek Tuff was emplaced around the caldera rim and within the caldera itself.

The explosions died away. A complex ecosystem was snuffed out and replaced by a sterile, steaming moonscape where hardly a living thing survived. The Yellowstone Plateau, the Teton Range, and thousands of surrounding square miles of Wyoming, Montana, and Idaho were barren and nearly lifeless for the third time in two million years.

The caldera-forming magma chamber, however, like our fizzed-out soda bottle, was far from empty. In fact, it may have contained 90 percent of its original magma volume. No sooner did the magma chamber roof collapse, than it began to rise again owing to pressures from underlying magma. Two resurgent domes soon began to form near the center of the elliptical caldera, one near Le Hardy Rapids on the Yellowstone River, and another east of Old Faithful.

The rejuvenated magma chamber also sent rhyolite to the surface where its eruption formed lava flows that buried part of the western resurgent dome and completely buried the caldera's western rim. Three such eruptive pulses about 150,000, 110,000, and 70,000 years ago produced about 240 cubic miles of rhyolite.

Because rhyolite lavas are rich in silica and poor in water, they tend to be quite viscous. Instead of flowing easily and rapidly as does Hawaiian basalt, rhyolite lava form piles of taffy-like incandescent rock whose margins will advance so slowly that observers will have to watch closely to see them moving.

Young rhyolite flows provide much of central Yellowstone's beauty; its lakes, waterfalls, and stream courses. For example, Yellowstone Lake fills a basin in the southeast part of the 600,000 year-old caldera between the east rim of the caldera and rhyolite flows on the west. Shoshone and Lewis lakes fill basins formed between adjacent flows. The Upper and Lower falls of the Yellowstone River tumble over resistant layers in caldera-filling flows. Nez Perce Creek, from its headwaters to its junction with the Firehole River, flows along a seam between lava flows. So does the Firehole River itself to its junction with the Madison River. The Gibbon River is pinched between younger flows and the Lava Creek Tuff through much of its course.

Driving west from Canyon Village you climb the steep eastern front of the Solfatara flow, drive miles across its rolling top, then descend its western slope to Gibbon River. Similarly, the drive from West Thumb to Old Faithful crosses several young rhyolite flows.

Silica, the primary constituent of rhyolite, provides a relatively sterile soil environment that is unfriendly to most living things. But not lodge pole pine. These hardy trees, pine grass, and fire-weed love such inhospitable sites. Their adaptability is why you see so many miles of boring lodge pole forest along Yellowstone roads.

In summary, three caldera eruptions and associated lava flows produced about 1,600 cubic miles of rhyolite in the last 2.1 million years. This staggering figure requires rates of magma production comparable to the most active volcanic regions on earth, such as Iceland and Hawaii. As we shall see, the processes that produced this enormous amount of magma also uplifted significant portions of northwestern Wyoming, southwestern Montana, and southern Idaho.

The Caldera Today

Is Yellowstone's history of volcanic activity at an end? Has time tamed its explosive violence, leaving only a heritage of aging geysers and eroding lava flows? Has the magma chamber beneath Yellowstone exhausted its supply of molten rock? Is it now incapable of producing more lava flows or explosions? Well, let's consider these questions; questions that have intrigued scientists ever since Yellowstone was discovered.

Anyone who has seen a geyser or hot spring immediately thinks of heat. Early geologists speculated that the heat in geyser waters came from the cooling of young lava flows beneath the geyser basins. They speculated that rain and snow melt water percolated into gravels and sands of the basins and into the young lava flows where it was heated before rising to the surface via geysers and hot springs. The lava flows were thought to be young, but even the most daring geologist tucked them well back in time. As we learned in Chapter 4, however, U. S. Geological Survey studies that dated the lava flows found some of them to be rather young, indeed.

Given that the youngest lava flows are only 70,000 years old, yesterday in geologic time, might not there still be molten magma beneath Yellowstone today? Direct methods, such as deep drilling, have not been employed to test this possibility, but other methods suggest magma exists beneath Yellowstone.

The earth's interior is warmer than its surface causing heat flow outward to the surface. The flow of heat in geyser basins is hundreds of times greater than normal heat flows. If the total conductive heat flow of major hydrothermal basins is averaged over the 965 sq. miles of the Yellowstone Caldera, we find flow levels that are 60 times greater than mean global rates.

Geophysical studies monitor the caldera and its magma body indirectly. From seismic studies we learn that shock waves from earthquakes and man-caused explosions traveling through the earth's crust are slowed significantly as they pass beneath the caldera. Material with a seismic velocity that is slower than normal underlies the caldera at depths as shallow as I mile. This may indicate local zones of molten magma in the upper crust. Near the northeast part of the caldera, seismic velocities are even lower to within about 2 miles of the surface; this may indicate a more continuous magma body that extends from the northeastern part of the caldera to about 10 miles beyond it. Down below the crust and in the mantle at depths of 100 miles, lower than normal local seismic velocities may indicate thin rising columns of magma.

Earthquake data also suggest that soft or molten rock is close to the surface of Yellowstone. Minor earthquakes jiggle Yellowstone hundreds of times each year, but above the caldera the foci of these quakes are extremely shallow, less than three miles below the surface. These clues suggest that the material underlying Yellowstone is still very hot and ductile, as would be expected if a magma chamber still exists.

Gravity studies back up conclusions drawn from seismic data. We know that gravity values across the Yellowstone Plateau are much lower than normal, and low gravity values are associated with low rock densities. In Yellowstone the low densities imply molten, thermally expanded material. As you might expect, the lowest gravity anomalies are found in the same place where seismic velocities are slowest—under the northeast caldera rim and beyond.

Local uplift and subsidence within Yellowstone are fast enough to be measured by surveying techniques. Benchmarks, points of precisely measured altitude, were established along the road systems of Yellowstone in 1923. One center of uplift on these surveys is at Le Hardys Rapids in the central part of the Yellowstone caldera and 3 miles down the Yellowstone River from its outlet from Yellowstone Lake. Until 1985, these surveys showed uplift at a rate of about V^ inch a year centered on Le Hardys Rapids, with total uplift since 1923 of about 3 feet. The profile of the Yellowstone River on both sides of Le Hardys Rapids suggests this uplift has been going on for a much longer time. Upstream from Le Hardys Rapids, the Yellowstone River is remarkably tranquil with a low gradient, whereas downstream it is many times steeper. Carbon dating of muds in the drowned channel of the Yellowstone River upstream from Le Hardys Rapids shows this overall uplift cycle had started by 3,000 years ago. Surveys in 1986 and later show this pattern of uplift has changed to subsidence, also at a rate of about 1/2 inch a year. We do not know if the change after 1985 represents the start of a major interval of subsidence or a minor reversal in a longer interval of uplift, but surveys as recent as 1993 show subsidence.

These various investigations of hydrothermal features, heat flow, seis-micity, earthquakes, gravity, and historic altitude change give us an interesting picture of what underlies the Yellowstone Plateau. These conditions are consistent with a large, partly molten magma body at shallow depth that extends northeast of the caldera rim. Although rocks underlying the rest of the caldera have low densities and low seismic velocities, the variations are less extreme, so the rocks there may be very hot but not necessarily contain much molten magma.

Thus we see that Yellowstone's fires are only banked, not out. Geologists don't expect another caldera explosion any time soon, but sometime new lava flows quite likely will once again consume lodge pole forests, and a new generation of geysers will burst forth, perhaps in Hot Springs Basin.

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Grand Teton National Park
John D. Rockefeller, Jr. Memorial Parkway

Located at the heart of the Greater Yellowstone Ecosystem, the Rockefeller Parkway connects Grand Teton and Yellowstone National Parks. The late conservationist and philanthropist John D. Rockefeller, Jr. made significant contributions to several national parks including Grand Teton, Acadia, Great Smoky Mountains, and Virgin Islands.
In 1972 Congress dedicated a 24,000 acre parcel of land as John D. Rockefeller, Jr. Memorial Parkway to recognize his generosity and foresight. Congress also named the highway from the south boundary of Grand Teton to West Thumb in Yellowstone in honor of Rockefeller.
The parkway provides a natural link between the two national parks and contains features characteristic of both areas. In the parkway, the Teton Range tapers to a gentle slope at its northern edge, while rocks born of volcanic flows from Yellowstone line the Snake River and form outcroppings scattered atop hills and ridges.
Grand Teton National Park administers John D. Rockefeller, Jr. Memorial Parkway.

Grand Teton National Park was established in both 1929 and 1950? The original 1929 park protected the mountain peaks and the lakes near the base. The boundaries were later expanded in 1950 to include much of the adjacent valley floor.

Grand Teton National Park is a United States National park located in northwestern Wyoming south of Yellowstone National park. The park is named after Grand Teton, which at 13,770 feet (4,197 m), is the tallest mountain in the Teton Range.
The mountains were named by a French trapper who viewed them from the Idaho side of the range and called them tétons, the French word for "nipples" or "teats" (presumably referring to the shape of the peaks). It was established as a national park on February 26, 1929. The park covers 484 Miles(1,255 km²) of land and water.
There are nearly 200 miles (320 km) of trails for hikers to enjoy in Grand Teton National Park.
Part of the Rocky Mountains, the north-south-trending Teton Range rises from the floor of Jackson Hole without any foothills along a 40 mile (65 km) long by 7 to 9 miles (11 to 15 km) wide active fault-block mountain front system. In addition to 13,770 ft (4,197 m) high Grand Teton, another eight peaks are over 12,000 ft (3,660 m) above sea level. Seven of these peaks between Avalanche and Cascade canyons make up the often-photographed Cathedral Group.

Jackson Hole is a 55 mile (90 km) long by 6 to 13 mile (10 to 20 km) wide graben valley that has an average elevation of 6,800 ft (2,070 m) with its lowest point near the south park boundary at 6350 ft (1,935 m). The valley sits east of the Teton Range and is vertically displaced downward 30,000 ft (9,100 m) from corresponding rock layers in it, making the Teton Fault and its parallel twin on the east side of the valley normal faults with the Jackson Hole block being the hanging wall and the Teton Mountain block being the footwall. Grand Teton National Park contains the major part of both blocks. A great deal of erosion of the range and sediment filling the graben, however, yields a topographic relief of only up to 7,700 ft (2,350 m).
The glaciated range is composed of a series of horns and arêtes separated by U-shaped valleys headed by cirques and ended by moraines, making the Tetons a textbook example of alpine topography. Rubble piles left by ice age alpine glaciers impounded a series of interconnected lakes at the foot of the range (Jackson, Leigh, String, Jenny, Bradley, Taggart, and Phelps). The largest lake in the valley, Jackson Lake, was impounded by a recessional moraine left by a very large valley glacier as it retreated north out of Jackson Hole. Jackson Lake covers 25,540 acres (103.4 km²) and has a maximum depth of 438 feet (134 m). There are also over 100 alpine and backcountry lakes.

Just to the south is Burned Ridge, the same glacier's terminal or end moraine, which runs down the center of Jackson Hole roughly perpendicular to the range and cut in two by the Snake River. After exiting its dammed outlet at the southeast corner of Jackson Lake, the Snake runs down the valley and through the 10 mile (16 km) long glacial outwash plain south of Burned Ridge. The river's headwaters are in a part of the Teton Wilderness a short distance north in Yellowstone National Park and its destination is the Columbia River far to the west, which in turn empties into the Pacific Ocean. Terraces have been cut by the river into the moraines and outwash plain in the valley. About 50 miles (80 km) of the 1,056 miles (1,699 km) mile long Snake River winds through the park where it is fed by three major tributaries; Pacific Creek, Buffalo Fork, and the Gros Ventre River.
The local climate is a semi-arid mountain one with a yearly extreme high of 93 °F (34 °C) and extreme low of −46 °F (−43 °C). Average annual snowfall is 191 inches (490 cm) and average rainfall is 10 inches (250 mm). The coldest temperature ever recorded in Grand Teton National Park was −63 °F (−52 °C), and snow often blankets the landscape from early November to late April.

Geology
The rock units that make up the east face of the Teton Range are around 2500 million years old and made of metamorphosed sandstones, limestones, various shales, and interbeded volcanic deposits. Buried deep under Tertiary volcanic, sedimentary, and glacial deposits in Jackson Hole, these same Precambrian rocks are overlain by Paleozoic and Mesozoic formations that have long since been eroded away from atop the Tetons.
The Paleozoic-aged sediments were deposited in warm shallow seas and resulted in various carbonate rocks along with sandstones and shales. Mesozoic deposition transitioned back and forth from marine to non-marine sediments. In later Mesozoic, the Cretaceous Seaway periodically covered the region and the Sierran Arc to the west provided volcanic sediments.
A mountain-building episode called the Laramide orogeny started to uplift western North America 70 million years ago and eventually formed the Rocky Mountains. This erased the seaway and created fault systems along which highlands rose. Sediment eroded from uplifted areas filled-in subsiding basins such as Jackson Hole while reverse faults created the first part of the Teton Range in the Eocene epoch. Large Eocene-aged volcanic eruptions from the north in the Yellowstone-Absaroka area along with later Pleistocene-aged Yellowstone Caldera eruptions, left thick volcanic deposits in basins (see geology of the Yellowstone area).
The Teton Range started to grow along a north-south trending fault system next to Jackson Hole some 9 million years ago in the Miocene epoch. Then starting in the Pliocene, Lake Teewinot periodically filled Jackson Hole and left thick lakebed sediments. The lake was dry by the time a series of glaciations in the Pleistocene epoch saw the introduction of large glaciers in the Teton and surrounding ranges. During the coldest ice age these glaciers melded together to become part of the Canadian Ice Sheet, which carried away all soil from Jackson Hole and surrounding basins. Later and less severe ice ages created enough locally-deposited dirt in the form of moraines and till to repair much of this damage. Since then, mass wasting events such as the 1925 Gros Ventre landslide, along with slower forms of erosion, have continued to modify the area. On the floor of the Jackson Hole valley rise several landforms, one of the most conspicuous being Blacktail Butte.

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Somehow.. "I though I might find you here, staring at the mountains."

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