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Yellowstone Caldera

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Yellowstone Caldera, also known as the Yellowstone Plateau Volcanic Field, is a Quaternary caldera complex and volcanic plateau spanning parts of Wyoming, Idaho, and Montana. It is driven by the Yellowstone hotspot and is largely within Yellowstone National Park. The field comprises four overlapping calderas, multiple lava domes, resurgent domes, crater lakes, and numerous bimodal lavas and tuffs of basaltic and rhyolitic composition, originally covering about Template:Convert.

Volcanism began 2.15 million years ago and proceeded through three major volcanic cycles. Each cycle involved a large ignimbrite eruption, continental-scale ash-fall, and caldera collapse, preceded and followed by smaller lava flows and tuffs. The first and also the largest cycle was the Huckleberry Ridge Tuff eruption about 2.08 million years ago, which formed the Island Park Caldera. The most recent supereruption, about 0.63 million years ago, produced the Lava Creek Tuff and created the present Yellowstone Caldera. Post-caldera eruptions included basalt flows, rhyolite domes and flows, and minor explosive deposits, with the last magmatic eruption about 70,000 years ago. Large hydrothermal explosions also occurred during the Holocene.

From 2004 to 2009, the region experienced notable uplift attributed to new magma injection. The 2005 docudrama Supervolcano, produced by the BBC and the Discovery Channel, increased public attention on the potential for a future catastrophic eruption. The Yellowstone Volcano Observatory monitors volcanic activity and does not consider an eruption imminent. Imaging of the magma reservoir indicates a substantial volume of partial melt beneath Yellowstone that is not currently eruptible.

GeologyEdit

The Yellowstone Plateau Volcanic Field lies at the eastern end of the Snake River Plain and disrupts the continuity of the Laramide orogenic belt, which formed during the Late Cretaceous.Template:Sfn From about 53 to 43 million years ago, this area experienced significant andesitic volcanism exceeding Template:Convert in total volume, forming the Absaroka Volcanic Supergroup. Prominent peaks such as Mount Washburn and Eagle Peak are eroded remnants of these earlier stratovolcanoes.Template:Sfn Before the formation of the Yellowstone Plateau, the Teton Range and Madison Range were likely structurally continuous, as were the Red Mountains and Gallatin Range.Template:Sfn

Current Yellowstone volcanism is not a continuation of Laramide tectonism or the Absaroka volcanic province.Template:Sfn Instead, it is the most recent part of a linear age-progression of rhyolitic complexes along the Snake River Plain, extending at least 16 million years to the McDermitt caldera complex.Template:Sfn Large rhyolitic tuff supereruptions occurred at these older eruptive centers.Template:SfnTemplate:Sfn One is the 12.1 million-year-old Ibex Hollow Tuff from the Bruneau-Jarbidge volcanic field in southern Idaho, burying herds of Nebraska mammals under volcanic ash.Template:Sfn Older volcanics proposed to be part of this hotspot track include the 56 million-year-old Siletzia oceanic plateau and the 70 million-year-old Carmacks Group.Template:SfnTemplate:Sfn

The cause of the northeastward progression of volcanism is debated. Some models invoke only upper-mantle processes, such as mantle pushed upward by the leading edge of the subducting Farallon plate,Template:Sfn slab rollback,Template:Sfn a propagating rift,Template:Sfn or mantle convection driven by abrupt changes in thermal layer thickness at the continent–ocean boundary.Template:Sfn A proposed lower-mantle origin suggests a fragment of the subducting Farallon slab penetrated the [[transition zone (Earth)|Template:Convert discontinuity]], pushing up the lower mantle and triggering melting of water-rich transition zone beneath the western United States.Template:Sfn Alternatively, a long-lived mantle plume rooted at the core–mantle boundary has been proposed. The plume erupted the Columbia River Basalt Group and is now feeding the Yellowstone hotspot.Template:Sfn Seismic tomography has revealed a Template:Convert wide, cylindrical thermal anomaly extending from the deepest mantle to just beneath Yellowstone, supporting the mantle plume origin.Template:Sfn In this model, the North American Plate moves southwest at about Template:Convert per year over the relatively stationary plume, creating the observed age-progression of eruptive centers.Template:Sfn

Structure of calderasEdit

The northern and eastern extent of the first-cycle caldera are unknown due to burial, although it likely reached into the third-cycle caldera, perhaps east of the Central Plateau.Template:Sfn The Huckleberry Ridge Tuff in the Red Mountains is interpreted as thick intracaldera fill of the Island Park Caldera,Template:Sfn and Big Bend Ridge at the southwestern edge of the volcanic plateau is inferred to be part of its caldera wall.Template:Sfn A fault along the Snake River and Glade Creek, bounding the northern end of Teton Range and Huckleberry Ridge, is also thought to be part of the Island Park ring-fault.Template:Sfn It is not known whether any of the first-cycle caldera segments was resurgent.Template:Sfn

The second-cycle caldera is known as the Henry's Fork Caldera. Thurmon Ridge at the northwestern edge of the volcanic plateau is inferred to be its northern caldera wall.Template:Sfn The fault along Big Bend Ridge was reactivated, collapsing again during the second-cycle caldera formation.Template:Sfn Although basalt flows bury its southern and eastern boundary, a positive gravity anomaly indicates a circular caldera about Template:Convert in diameter, with its southern boundary in the middle of the Island Park basin.Template:Sfn

Robert L. Christiansen inferred that the Yellowstone Caldera is a compound caldera comprising two partially overlapping ring-fault zones, centered on the resurgent Mallard Lake dome and Sour Creek dome.Template:Sfn The southwest boundary is unconstrained due to post-caldera rhyolite burial, but he proposed that the south flank of Purple Mountain and the Washburn Range, along with the west flank of the Absaroka Range, mark the caldera boundary on the north and east sides.Template:Sfn Lewis Falls, Lake Butte, and Flat Mountain Arm of Yellowstone Lake are also part of the Yellowstone caldera rim.Template:Sfn However, the purported Sour Creek ring-fault zone and the location of the eastern caldera boundary have been challenged. More recent field mappings suggest the eastern ring-fault lies west of Sour Creek dome, closely following the Yellowstone River.Template:SfnTemplate:Sfn

The most western portion of Yellowstone Lake is the elliptical Template:Convert West Thumb Basin, which includes one of the lake’s deepest areas. It is interpreted as a fourth caldera, formed by a third-cycle post-caldera explosive eruption.Template:Sfn

File:Yellowstone Major Calderas Map.jpg
Yellowstone sits on top of four overlapping calderas (U.S. National Park Service).

Eruption historyEdit

A total of Template:Convert of rhyolite and Template:Convert of basalt were emplaced over three volcanic cycles between about 2.15 million and 0.07 million years ago.Template:Sfn Each cycle lasted roughly three-quarters of a million years. The sequence of events in each cycle is similar: a catastrophic rhyolitic ash-flow sheet and caldera collapse, preceded and followed by eruptions of rhyolitic lavas and tuffs and basaltic eruptions near the caldera margin.Template:Sfn Ash-flow sheets account for more than half of the total volcanic volume of the Yellowstone Plateau.Template:Sfn

First-cycleEdit

File:Map Volcanic Ashes Yellwostone Eruptions color.png
Map of the known ash-fall boundaries for major Pleistocene eruptions in Southwest US. By Volcano Hazards Program

The first-cycle lasted from about 2.15 million to 1.95 million years ago, spanning approximately 200 kyr.Template:Sfn The only known pre-collapse rhyolitic unit is the Rhyolite of Snake River Butte, located just north of Ashton and dated at Template:Value,Template:Sfn roughly 60–70 kyr before the caldera-forming Huckleberry Ridge Tuff.Template:Sfn Its vent lies near the eventual first-cycle caldera margin close to the Big Bend Bridge.Template:Sfn Additional rhyolite flows may have erupted along the incipient ring-fault,Template:Sfn but the pre-collapse rhyolite history likely spans no more than ~70 kyr.Template:Sfn Another pre-collapse unit is the Template:Convert-thick Junction Butte Basalt on the northeastern margin of the plateau,Template:Sfn dated at Template:Value.Template:Sfn The Overhanging Cliff basalt is a flow of this unit.Template:Sfn

The first-cycle caldera-forming event was the eruption of the Huckleberry Ridge Tuff at Template:Value ago, during transitional magnetic polarity.Template:Sfn Its thickness exceeds Template:Convert in the Red Mountains area.Template:Sfn The initial Plinian phase deposited up to Template:Convert of fallout ash at Mount Everts before transitioning to ash-flow tuff.Template:SfnTemplate:Sfn Early Plinian activity was intermittent, sourced from multiple vents, probably lasted a few weeks and evacuated about Template:Convert of magma from four magma bodies,Template:Sfn triggering caldera collapse at the onset of transition to ash-flow.Template:SfnTemplate:Sfn The ash-flow tuff is a composite sheet consisted of three intermittent members, with a total magma volume of about Template:Convert.Template:Sfn Member A likely vented from the plateau's central areaTemplate:Sfn and tapped nine magma bodies.Template:Sfn After a hiatus of a few weeks or more,Template:Sfn the most voluminous Member B erupted from north of Big Bend Ridge.Template:Sfn After another extended break of years to decades,Template:Sfn part of the Member A magmatic system was rejuvenated to feed Member C.Template:Sfn The least voluminous Member C might have source area near the Red Mountains, where it is about Template:Convert thick.Template:Sfn Some outcrops of Member A and Member C have been misidentified as Member B, complicating volume estimates of individual ash-flow unit.Template:Sfn Glen A. Izett estimated that an additional Template:Convert of ash was dispersed as fallout across North America.Template:Sfn Tephra fallout from this event is known as the Huckleberry Ridge ash bed (formerly "Pearlette type B"). Its area covered exceeds Template:Convert.Template:Sfn. It is widely distributed and has been identified in the Pacific Ocean at Deep Sea Drilling Project Site 36, about Template:Convert from Island Park Caldera,Template:Sfn as well as in the Humboldt and Ventura basins of coastal California,Template:Sfn near Afton in Iowa, Benson in Arizona, and Campo Grande Mountain in Texas.Template:Sfn

One lava flow near the Sheridan ReservoirTemplate:Sfn and two flows at the north end of Big Bend RidgeTemplate:Sfn are post-collapse rhyolites of the first-cycle volcanism. The Sheridan Reservoir Rhyolite, dated at Template:Value,Template:Sfn if vented from the Island Park ring-fracture, required a flow distance of at least Template:Convert.Template:Sfn Its volume is estimated to exceed Template:Convert.Template:Sfn The other two flows, the Blue Creek flow and the overlying Headquarters flow, have a combined volume of Template:ConvertTemplate:Sfn and erupted respectively at Template:Value and Template:Value ago.Template:Sfn

Second-cycleEdit

After ~500 kyr of quiescence,Template:Sfn a new magmatic system formed north of Big Bend Ridge. It erupted the Bishop Mountain Flow at Template:Value and the Tuff of Lyle Spring at Template:Value.Template:Sfn The Bishop Mountain Flow is a rhyolite with an exposed volume of about Template:Convert and reaches a thickness of Template:Convert along the inner caldera wall. The Tuff of Lyle Spring is a Template:Convert, composite ash-flow sheet consisting of two cooling units.Template:Sfn Both eruptions appear to have originated from an isolated, highly evolved local magma chamber distinct from the second-cycle magma source.Template:Sfn Tiffany A. Rivera et al. (2017) suggest these two eruptions should not be assigned to the second cycle but instead represent the separate Lyle Spring magmatic system.Template:Sfn The next pre-collapse rhyolite eruption is the Green Canyon Flow in the north of Big Bend Ridge, with a mapped volume of about Template:Convert, dated at Template:Value.Template:Sfn Its age is indistinguishable from that of the subsequent Mesa Falls Tuff, but the Henry's Fork Caldera fracture truncates the Green Canyon Flow, indicating it predates the second-cycle caldera.Template:Sfn

The second-cycle caldera-forming eruption was the Mesa Falls Tuff, dated at Template:Value.Template:Sfn Its exposed thickness exceeds Template:Convert on Thurmon Ridge, though it is likely much thicker within the caldera.Template:Sfn During the initial Plinian phase, about Template:Convert of ash and pumice were deposited around the Ashton area, while much of the vitric ash dispersed to more distant regions, as inferred from the high crystal content of the local deposit. This airfall is overlain by a Template:Convert pyroclastic surge layer also enriched in crystals.Template:Sfn A single cooling unit of ash-flow tuff followed, covering about Template:Convert with an estimated volume of Template:Convert.Template:Sfn The Mesa Falls ash bed (formerly "Pearlette type S") is the distal ash-fall of this eruption, found in Brainard and Hartington in Nebraska, and in the southern Rocky Mountains of Colorado.Template:Sfn

Post-collapse eruptions included the Moonshine Mountain domeTemplate:Sfn and five rhyolite domes collectively known as the Island Park Rhyolite.Template:Sfn The Moonshine Mountain dome, with an estimated volume of Template:Convert, erupted at Template:Value.Template:Sfn While its age is indistinguishable from the Mesa Falls Tuff, field evidence indicates it formed after the collapse of the Henry's Fork Caldera.Template:Sfn The dome's magma source is likely the same region that supplied the Bishop Mountain Flow.Template:Sfn The Island Park Rhyolite comprises five bodies: Silver Lake dome, Osborne Butte dome, Elk Butte dome, Lookout Butte dome, and Warm River Butte dome.Template:Sfn These domes collectively have a total volume of Template:Convert.Template:Sfn All five erupted within a few centuries, around Template:Value, during a single eruptive episode.Template:Sfn While Lookout Butte is located on the rim of Big Bend Ridge caldera wall, the vents for the other four domes align along a northwest-trending, structurally controlled linear vent zone about Template:Convert long and no more than Template:Convert wide.Template:Sfn

Third-cycleEdit

Pre-collapse third-cycle silicic rocks are broadly divided into the Mount Jackson Rhyolite and the Lewis Canyon Rhyolite,Template:Sfn which vented along what later became the ring-fracture zone of the third-cycle caldera.Template:Sfn The earliest known lava in this cycle is the Wapiti Lake flow of the Mount Jackson group, dated at Template:Value,Template:Sfn exposed near the Grand Canyon of the Yellowstone and likely vented near Wapiti Lake.Template:Sfn Another flow, the Moose Creek Butte flow (Template:Value), also belongs to the Mount Jackson group.Template:Sfn Although younger than the Island Park Rhyolite, its geochemical similarity has led some researchers to propose it as a second-cycle post-collapse eruption.Template:Sfn Pumice of an unknown tuff unit at Broad Creek has an age range from Template:Value to Template:Value.Template:Sfn Later Mount Jackson eruptions include the Flat Mountain Rhyolite (Template:Value)Template:Sfn and the Harlequin Lake flow (Template:Value).Template:Sfn The Lewis Canyon Rhyolite group contains lavas dated to Template:Value,Template:Sfn though Robert L. Christiansen suggests they could be late-stage first-cycle eruptions.Template:Sfn A recently discovered ash-flow unit is dated to Template:Value.Template:Sfn An explosive eruption deposited pumiceous fallout near Harlequin Lake,Template:Sfn which is immediately overlain by the Mount Haynes lava (Template:Value).Template:Sfn An ash bed from a Yellowstone eruption was deposited in the Great Salt Lake approximately Template:Value ago.Template:Sfn The age of the Big Bear Lake flow is uncertain, but it lies beneath the third-cycle caldera-forming Lava Creek Tuff.Template:Sfn Additional Mount Jackson flows may be buried within the Yellowstone caldera, inferred from intracaldera topography.Template:Sfn

The climatic ash-flow eruption of the third cycle was the Lava Creek Tuff, dated at Template:Value,Template:Sfn during a glacial–interglacial transition in the Marine Isotope Stage.Template:Sfn This composite tuff sheet consists of at least two members, distinguishable by a widely occurring welding intensity decrease between them,Template:Sfn and represents a total ash-flow volume of about Template:Convert.Template:Sfn Member A likely erupted south of Purple Mountain, where it reaches its greatest thickness of Template:Convert and exhibits maximum welding.Template:Sfn The Purple Mountain to Gibbon Canyon segment of caldera wall collapsed after the emplacement of Member A but before it completely cooled.Template:Sfn A Template:Convert loose crystal ash unit separates Member A from Member B, indicating a break in the eruption sufficiently long for cooling of thick ash-flows.Template:Sfn A Template:Convert thick pumiceous ash-fall deposit underlies Member B and probably marks its initial phase.Template:Sfn Member B ash-flows extends radially outward along paleovalleys and more extensive plateau segments. The eruptive center for Member B appears to be situated farther east compared to that of Member A.Template:Sfn However, this simplistic eruptive sequence has been challenged.Template:Sfn An additional Template:Convert ash-flow unit (informally named unit 2) has been identified, venting from around Bog Creek. Unit 2 erupted some decades after Member A had cooledTemplate:Sfn and overlies tuff fragments from Member A.Template:Sfn Two additional rhyolite ash-flow units (unit 3 and unit 4) have been recognized, erupting from a vent near Stonetop Mountain and are previously undocumented parts of the Lava Creek Tuff.Template:Sfn An unknown welded tuff underlying Member B at Flagg Ranch, not attributed to Member A, was emplaced shortly before the initial ashfall of Member B and is considered part of the early Lava Creek eruption.Template:Sfn Rather than having the simple structure of just two ignimbrite sheets, the Lava Creek Tuff may consist of multiple ash-flow lobes from distinct magma bodies.Template:Sfn The ash fallout from the Lava Creek Tuff eruption is known as the Lava Creek ash bed (formerly "Pearlette type O"),Template:Sfn covering an area exceeding Template:Convert.Template:Sfn Perkins and Nash (2002) estimated that the volume of this ash bed is greater than Template:Convert.Template:Sfn It has been identified in the Gulf of Mexico,Template:Sfn near Regina, Saskatchewan,Template:Sfn in Ventura, California,Template:Sfn and in Viola Center, Iowa.Template:Sfn

Post-collapse rhyolitesEdit

Post-collapse rhyolites likely erupted shortly after the Lava Creek Tuff.Template:Sfn The subaerial post-collapse silicic rocks are collectively referred to as the Plateau Rhyolite,Template:Sfn which primarily consists of lava flows.Template:Sfn Plateau Rhyolite is divided into three intracaldera members—Upper Basin Member, Mallard Lake Member, and Central Plateau Member—and two extracaldera members—Obsidian Creek Member and Roaring Mountain Member.Template:Sfn It is likely that rhyolitic pumice and ash were erupted during the opening of vents for each of these lava flows.Template:Sfn The earliest intracaldera rhyolite, the East Biscuit Basin Flow of the Upper Basin Member, is dated to Template:Value, followed by felsic lithic clasts of an unknown unit (Template:Value) in Yellowstone Lake,Template:Sfn and the North Biscuit Basin Flow (Template:Value).Template:Sfn The earliest extracaldera rhyolite is the Riverside Flow (Template:Value) of the Roaring Mountain Member,Template:Sfn broadly contemporaneous with the Middle Biscuit Basin Flow (Template:Value).Template:Sfn Two ash-flow tuff units of the Upper Basin Member include the Template:Convert-thick Tuff of Uncle Tom’s TrailTemplate:Sfn and the Template:Convert-thick Tuff of Sulphur CreekTemplate:Sfn, the latter dated at Template:Value.Template:Sfn Tuff of Sulphur Creek is at least Template:Convert.Template:Sfn These tuffs were deposited on the north flank of the Sour Creek dome.Template:Sfn The Canyon lava flows of the Upper Basin Member erupted immediately after the Tuff of Sulphur Creek, as the ash-flow was still hot at the time of emplacement.Template:Sfn Both the Tuff of Sulphur Creek and Canyon flows originated from a vent near Fern Lake.Template:Sfn The two tuffs and Canyon flows have a combined magma volume of Template:Convert.Template:Sfn The Dunraven Road Flow (Template:Value) of the Upper Basin Member overlies the Canyon flowsTemplate:Sfn and may have had an extracaldera vent.Template:Sfn The Cougar Creek lava dome of the Roaring Mountain Member erupted Template:Value north of the caldera.Template:Sfn Four additional lava flows of the Obsidian Creek Member—Willow Park dome, Apollinaris Spring dome, Gardner River complex, and Grizzly Lake complex—erupted between Template:Value and Template:Value,Template:Sfn in the vicinity of Norris Geyser Basin northward toward Mammoth Hot Springs.Template:Sfn The South Biscuit Basin Flow of the Upper Basin Member erupted Template:Value ago.Template:Sfn The Scaup Lake Flow of the Upper Basin Member is dated to Template:Value,Template:Sfn while the Landmark dome of the Obsidian Creek Member is Template:Value.Template:Sfn

Non-explosive eruptions of lava and less-violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The most recent lava flow occurred about 70,000 years ago, while a violent eruption excavated the West Thumb of Lake Yellowstone 174,000 years ago. Smaller steam explosions occur as well. An explosion 13,800 years ago left a Template:Convert diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Currently, volcanic activity is exhibited via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser, plus recorded ground-swelling indicating ongoing inflation of the underlying magma chamber.Template:Citation needed

HazardsEdit

EarthquakesEdit

File:Yellowstone earthquakes history.svg
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Volcanic and tectonic actions in the region cause between 1,000 and 2,000 measurable earthquakes annually. Most are relatively minor, measuring magnitude 3 or weaker. Occasionally, numerous earthquakes are detected in a relatively short period of time, an event known as an earthquake swarm. In 1985, more than 3,000 earthquakes were measured over a period of several months. More than 70 smaller swarms were detected between 1983 and 2008. The USGS states these swarms are likely caused by slips on pre-existing faults rather than by movements of magma or hydrothermal fluids.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="volcanoes.usgs.gov">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In December 2008, continuing into January 2009, more than 500 earthquakes were detected under the northwest end of Yellowstone Lake over a seven-day span, with the largest registering a magnitude of 3.9.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Another swarm started in January 2010, after the Haiti earthquake and before the Chile earthquake. With 1,620 small earthquakes between January 17, 2010, and February 1, 2010, this swarm was the second-largest ever recorded in the Yellowstone Caldera. The largest of these shocks was a magnitude 3.8 that occurred on January 21, 2010.<ref name="volcanoes.usgs.gov"/><ref>Template:Cite news</ref> This swarm subsided to background levels by February 21. On March 30, 2014, at 6:34 AM MST, a magnitude 4.8 earthquake struck Yellowstone, the largest recorded there since February 1980.<ref>Template:Cite news
Template:Cite news</ref> In February 2018, more than 300 earthquakes occurred, with the largest being a magnitude 2.9.<ref>Template:Cite news
Template:Cite magazine</ref>

VolcanoesEdit

File:Yellowstone Caldera.svg
Diagram of the Yellowstone Caldera

The Lava Creek eruption of the Yellowstone Caldera, which occurred 640,000 years ago,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> ejected approximately Template:Convert of rock, dust and volcanic ash into the atmosphere. It was Yellowstone's third and most recent caldera-forming eruption.

Geologists closely monitor the elevation of the Yellowstone Plateau, which has been rising as quickly as Template:Convert per year, as an indirect measurement of changes in magma chamber pressure.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite press release</ref><ref>Template:Cite journal</ref>

The upward movement of the Yellowstone caldera floor between 2004 and 2008—almost Template:Convert each year—was more than three times greater than ever observed since such measurements began in 1923.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> From 2004 to 2008, the land surface within the caldera moved upward as much as Template:Convert at the White Lake GPS station.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> In January 2010, the USGS stated that "uplift of the Yellowstone Caldera has slowed significantly"<ref>Current Alerts for U.S. Volcanoes. volcano.wr.usgs.gov</ref> and that uplift continues but at a slower pace.<ref>GPS Station: WLWY – Data Products – Time Series Plots. unavco.org</ref> USGS, University of Utah and National Park Service scientists with the Yellowstone Volcano Observatory maintain that they "see no evidence that another such cataclysmic eruption will occur at Yellowstone in the foreseeable future. Recurrence intervals of these events are neither regular nor predictable." This conclusion was reiterated in December 2013 in the aftermath of the publication of a study by University of Utah scientists finding that the "size of the magma body beneath Yellowstone is significantly larger than had been thought". The Yellowstone Volcano Observatory issued a statement on its website stating:

Although fascinating, the new findings do not imply increased geologic hazards at Yellowstone, and certainly do not increase the chances of a "supereruption" in the near future. Contrary to some media reports, Yellowstone is not "overdue" for a supereruption.<ref>Template:Cite press release</ref>

Media reports were more hyperbolic in their coverage.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

A study published in GSA Today, the monthly news and science magazine of the Geological Society of America, identified three fault zones where future eruptions are most likely to be centered.<ref name="NG">Template:Cite magazine</ref> Two of those areas are associated with lava flows aged 174,000–70,000 years ago, and the third is a focus of present-day seismicity.<ref name=NG />

In 2017, NASA conducted a study to determine the feasibility of preventing the volcano from erupting. The results suggested that cooling the magma chamber by 35 percent would be enough to forestall such an incident. NASA proposed introducing water at high pressure 10 kilometers underground. The circulating water would release heat at the surface, possibly in a way that could be used as a geothermal power source. If enacted, the plan would cost about $3.46 billion. Brian Wilcox of the Jet Propulsion Laboratory observes that such a project could incidentally trigger an eruption if the top of the chamber is drilled into.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

According to analysis of earthquake data in 2013, the magma chamber is Template:Convert long and Template:Convert wide. It also has Template:Convert underground volume, of which 6–8% is filled with molten rock. This is about 2.5 times bigger than scientists had previously imagined; however, scientists believe that the proportion of molten rock in the chamber is too low to allow for another supereruption.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In October 2017, research from Arizona State University indicated prior to Yellowstone's last supereruption, magma surged into the magma chamber in two large influxes. An analysis of crystals from Yellowstone's lava showed that prior to the last supereruption, the magma chamber underwent a rapid increase in temperature and change in composition. The analysis indicated that Yellowstone's magma reservoir can reach eruptive capacity and trigger a super-eruption within just decades, not centuries as volcanologists had originally thought.<ref name="may erupt sooner">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="seek clues">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Hydrothermal explosionsEdit

Template:Further

File:HotspotsSRP update2013.JPG
Path of the Yellowstone hotspot over the past 16 million years

The volcanic eruptions, as well as the continuing geothermal activity, are a result of a great plume of magma located below the caldera's surface. The magma in this plume contains gases that are kept dissolved by the immense pressure under which the magma is contained. If the pressure is released to a sufficient degree by some geological shift, then some of the gases bubble out and cause the magma to expand. This can cause a chain reaction. If the expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very large gas explosion.Template:Citation needed

Studies and analysis may indicate that the greater hazard comes from hydrothermal activity which occurs independently of volcanic activity.Template:Citation needed Over 20 large craters have been produced in the past 14,000 years, resulting in such features as Mary Bay, Turbid Lake, and Indian Pond, which was created in an eruption about 1300 BC.Template:Citation needed

In a 2003 report, USGS researchers proposed that an earthquake may have displaced more than Template:Convert of water in Yellowstone Lake, creating colossal waves that unsealed a capped geothermal system and led to the hydrothermal explosion that formed Mary Bay.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite news</ref>

Further research shows that very distant earthquakes reach and have effects upon the activities at Yellowstone, such as the 1992 7.3 magnitude Landers earthquake in California's Mojave Desert that triggered a swarm of quakes from more than Template:Convert away, and the 2002 7.9 magnitude Denali fault earthquake Template:Convert away in Alaska that altered the activity of many geysers and hot springs for several months afterward.<ref>Template:Cite news</ref>

In 2016, the USGS announced plans to map the subterranean systems responsible for feeding the area's hydrothermal activity. According to the researchers, these maps could help predict when another eruption occurs.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Cultural significanceEdit

IUGS geological heritage siteEdit

In respect of it being "well-known for its past explosive volcanic eruptions and lava flows as well for its world class hydrothermal system", the International Union of Geological Sciences (IUGS) included "The Yellowstone volcanic and hydrothermal system" in its assemblage of 100 geological heritage sites around the world in a listing published in October 2022. The organization defines an IUGS Geological Heritage Site as "a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history".<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

See alsoEdit

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ReferencesEdit

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SourcesEdit

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Further readingEdit

External linksEdit

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