USGS/Cascades Volcano Observatory, Vancouver, Washington
DESCRIPTION:
Yellowstone Caldera, Wyoming
- Yellowstone Caldera
- Yellowstone Plateau
- Snake River Plain - Yellowstone Volcanic Province
- Yellowstone Hydrothermal Systems
- Yellowstone "Hot Spot"
- Yellowstone's Eruptive History
- Supervolcano
-
[Image,60K,JPG]
Yellowstone Falls, Yellowstone Caldera, Wyoming
-- USGS Photo by David E. Wieprecht
Compiled From:
1
Smithsonian Institution - Global Volcanism Program Website, 1998,
and 2 Wright and Pierson, 1992, Living With Volcanoes, The U. S. Geological Survey's Volcano Hazards Program: USGS Circular 1073
- Yellowstone Caldera
- Location: Wyoming, Montana, Idaho
- Latitude: 44.43 N
- Longitude: 110.67 W
- Height: 2,805 Meters
- Type:
Calderas
- Number of eruptions in past 200 years: 0
- Latest Eruptions: 70,000 years ago
- Present thermal activity: Numerous hydrothermal activity
- Remarks:
Numerous hydrothermal explosions, geysers, geothermal activity; currently restless, shown by seismicity and ground deformation 2
From: U.S. National Park Service Website, Geology Fieldnotes -
Yellowstone National Park, April 2000 - At the
heart of Yellowstone's past, present, and future lies volcanism. Catastrophic eruptions occurred here about 2 million years ago, then 1.2 million years
ago, and then 600,000 years a
go. The latest eruption spewed out nearly 240
cubic miles of debris.
What is now the park's central portion then collapsed,
forming a 28- by 47- mile
caldera
(or basin). The magmatic heat
powering those eruptions still powers the park's famous geysers, hot springs,
fumaroles, and mud pots. The spectacular Grand Canyon of the Yellowstone River
provides a glimpse
of Earth's interior: its waterfalls highlight
the boundaries of lava flows and thermal areas.
Rugged
mountains flank the park's volcanic plateau, rewarding both eye and spirit.
From: Brantley, 1994, Volcanoes of the United States:
USGS General Interest Publication
-
Yellowstone Caldera
is one of the largest and most active
calderas
in the world. The spectacular
geysers, boiling hot springs, and mud pots
that have made Yellowstone famous -- and even the strikingly beautiful
Grand Canyon of Yellowstone through which the Yellowstone River plunges --
owe their existence to the tremendous volcanic forces that have affected
the region during the past 2 million years.
Cataclysmic eruptions 2.0, 1.3, and 0.6 million years ago ejected huge
volumes of rhyolite magma; each eruption formed a caldera and extensive
layers of thick pyroclastic-flow deposits. The youngest caldera is an
elliptical depression, nearly 80 kilometers long and 50 kilometers wide,
that occupies much of
Yellowstone National Park.
The caldera is buried by several extensive rhyolite lava flows erupted between
75,000 and 150,000 years ago.
-
The Earth's crust beneath Yellowstone National Park is still restless.
Precise surveys have detected an area in the center of the caldera that rose
by as much as 86 centimeters between 1923 and 1984 and then subsided slightly
between 1985 and 1989. Scientists do not know the cause of these ups and
downs but hypothesize that they are related to the addition or withdrawal of magma
beneath the caldera, or to the changing pressure of the hot groundwater system
above Yellowstone's large magma reservoir. Also, Yellowstone National Park and the
area immediately west of the Park are historically among the most seismically
active areas in the Rocky Mountains.
Small-magnitude earthquakes are common beneath the entire caldera,
but most are located along the Hebgen Lake fault zone that extends into the
northwest part of the caldera. A magnitude 7.5 earthquake occurred along this
zone in 1959
[Map,20K,InlineGIF].
From: Newhall and Dzurisin, 1988, Historical Unrest at Large Calderas in the World:
USGS Bulletin 1855
-
The Yellowstone region has produced three
caldera-forming eruptions
in the past 2 million years, two of those among the largest eruptions
known to have occurred on Earth (each more than 1,000 cubic kilometers).
Yellowstone's
hydrothermal system
is among the largest and most active in the world, and its historical seismicity and
uplift are comparable to those at the most active
calderas ...
From: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.263-267, Contribution by R. L. Christiansen
- The Yellowstone Plateau spans the continental divide between the
Northern and Middle Rocky Mountains, at an average elevation of around 2,400 meters.
The
plateau
lies at the center of one of the Earth's largest volcanic fields, entirely post-dating
2.5 million years ago. The major eruptions of the volcanic field were exceedingly
voluminous, but their products are only surficial expressions of the emplacement of a
batholithic volume of rhyolitic magma to high crustal levels in several episodes.
The total volume of magma erupted from the Yellowstone Plateau volcanic field
since 2.5 million years ago probably approaches 6,000 cubic kilometers.
- This great magmatic volume and the enormous
calderas
produced by the largest pyroclastic eruptions are associated with a surprisingly
subtle morphology. The Yellowstone caldera,
the youngest of three nested and overlapping calderas, is filled by younger rhyolitic lavas,
and is readily recognizable in only one or two sectors.
The two older, nested calderas, however, form part of a conspicuous
circular basin at the west edge of the volcanic field, called Island Park
which is enclosed along its eastern margin by a younger constructional lava platform
at the west edge of the Yellowstone Plateau.
Snake River Plain - Yellowstone Volcanic Province
|
From: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.149-150, Contribution by Charles A. Wood.
-
An 80-kilometer-wide swath of basaltic and rhyolitic volcanism cuts across southeast
Idaho
for 450 kilometers. This
Snake River Plain-Yellowstone (SRPY) volcanic province
is the most dynamic area of volcanism in North America.
This is not because of abundant historic eruptions -- there have been none --
but rather because of its rapid motion. SRPY is propagating to the northeast
at 3.5 centimeters per year (Armstrong, et.al., 1975);
it will slice through Montana and be at the Canadian border
in approximately 20 million years. If past activity is a guide, SRPY
doesn't simply cover terrain with volcanic rocks, but rather the pre-existing
ground subsides up to 6 kilometers (Braile, et.al., 1982) between major faults
(Sparlin, et.al., 1982) and is further churned up by the transit of magma
and the formation of magma chambers. SRPY is a geologic roto-tiller.
-
According to the radiometric dating of Armstrong, et.al. (1975),
SRPY activity began approximately 15 million years ago with
silicic volcanism in southern Idaho. A series of now buried rhyolitic
calderas
formed in a northeast progression, with abundant basaltic volcanism lagging
behind by 2-5 million years. Island Park and the two Yellowstone calderas
Island Park is now being colonized by the basaltic wave of magma. ...
Yellowstone Hydrothermal Systems
|
From: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.263-267, Contribution by R. L. Christiansen
- The Yellowstone caldera region hosts the world's largest know
hydrothermal system,
highlighted by numerous geysers. This hydrothermal system accounts for an
average heat flow from the caldera area 40 times greater than the global average.
Although the latest eruptions were approximately 70,000 years ago, the immense
hydrothermal system and a variety of geophysical characteristics indicate that
magma still underlies the Yellowstone caldera at a shallow depth.
A large negative gravity anomaly, low magnetic intensity, high electrical
conductivity, shallow swarm seismicity, and large delays and high attenuation of
seismic waves are all consistent with this inference.
-
Yellowstone is the oldest
national park
in the world and one of the leading tourist attractions in North America.
U. S. Highways 16, 212, and 289 go through the Park. Many hydrothermal and volcanic
features are marked.
From:
Dzurisin, Christiansen, and Pierce, 1995, Yellowstone:
Restless Volcanic Giant: VOLCANO HAZARDS FACT SHEET:
USGS Open-File Report 95-59
-
Scientists have traced Yellowstone's origin to a
hot spot
in the mantle, one of a few dozen such hot spots on Earth. Buoyant material from a hot spot rises through the upper mantle, bringing heat from the Earth's interior closer to the surface. The Yellowstone hot spot impinges on the base of the North American plate, one of several rigid plates that make up the Earth's crust. These plates move a few inches per year with respect to the stationary hot spots and each other, sometimes causing great earthquakes as the plates collide, grind past one another, or split apart.
From: Newhall and Dzurisin, 1988, Historical Unrest at Large Calderas in the World: USGS Bulletin 1855
-
Yellowstone lies at the intersection of the Basin and Range tectonic province,
dominated by E-W extension, and the eastern
Snake River Plain,
a linear downwarp or graben that has been a locus for basaltic volcanism since middle
Miocene time.
According to one popular model, the rhyolitic Yellowstone Plateau
marks the current location of a
"hotspot"
or melting anomaly in the upper mantle, and the basaltic Snake River Plain
records the hotspot's northeastward track across the mobile North American Plate. ...
From: Kious and Tilling, 1996, This Dynamic Earth: The Story of Plate Tectonics:
USGS Special Interest Publication
-
A few hotspots are thought to exist below the
North American Plate.
Perhaps the best known is the hotspot presumed to exist under the continental crust in the region of
Yellowstone National Park
in northwestern Wyoming. Here are several calderas
(large craters formed by the ground collapse accompanying explosive volcanism)
that were produced by three gigantic eruptions during the past two million years, the most recent of which occurred about 600,000 years ago. Ash deposits from these powerful eruptions have been mapped as far away as Iowa, Missouri, Texas, and even northern Mexico.
The thermal energy of the presumed Yellowstone hotspot fuels more than 10,000 hot pools and springs, geysers (like Old Faithful), and bubbling mudpots (pools of boiling mud). A large body of magma, capped by a hydrothermal system (a zone of pressurized steam and hot water), still exists beneath the caldera. Recent surveys demonstrate that parts of the Yellowstone region rise and fall by as much as 1 cm each year, indicating the area is still geologically restless. However, these measurable ground movements, which most likely reflect hydrothermal pressure changes, do not necessarily signal renewed volcanic activity in the area.
Yellowstone's Eruptive History
|
From: Newhall and Daniel Dzurisin, 1988, Historical Unrest at Large Calderas of the World:
U.S. Geological Survey Bulletin 1855
-
Yellowstone lies at the intersection of the Basin and Range tectonic province, dominated by E-W extension, and the eastern
Snake River Plain,
a linear downwarp or graben that has been a locus for basaltic volcanism since
middle Miocene
time. According to one popular model, the rhyolitic Yellowstone Plateau marks the current location of a
"hotspot"
or melting anomaly in the upper mantle, and the basaltic Snake River Plain records the hotspot's northeastward track across the mobile
North American Plate.
-
Focal mechanisms of a magnitude 7.5 earthquake and its aftershocks (Hebgen Lake, 1959) suggested N-S extension near Hebgen Lake (about 70 kilometers northwest of Yellowstone) and radial compression near the caldera. Focal mechanisms of more recent earthquakes and geologic mapping in the caldera suggest dominant ENE-WSW or E-W extension.
-
Three times in the past 2 million years, large reservoirs of rhyolite magma have accumulated in the upper crust at Yellowstone, triggering cataclysmic eruptions and
caldera collapses
2.0, 1.3, and 0.6 million years ago. The first great eruption (2.0 million years B.P.)
produced the
Huckleberry Ridge Tuff (more than 2,450 cubic kilometers) and a composite caldera
more than 75 kilometers long, extending from Island Park on the west to central
Yellowstone Park on the east. The second eruption (1.3 m.y. B.P.) produced the
Mesa Falls Tuff (more than 280 cubic kilometers) and the Island Park Caldera
west of Yellowstone Park; the third (0.6 m.y. B.P.) produced the Lava Creek Tuff
(more than 1,000 cubic kilometers) and the present Yellowstone Caldera.
Rhyolitic volcanism resumed within the Yellowstone Caldera after structural
resurgence formed the Sour Creek and Mallard Lake
resurgent domes.
Renewed doming in the western caldera culminated with extrusion of 1,000 cubic
kilometers of intracaldera rhyolite flows between 150,000 and 75,000 years ago.
-
There is abundant geophysical evidence for residual partial melt beneath
Yellowstone Caldera, and the consensus among those who have studied
the area is that the Yellowstone magmatic system will likely erupt again.
-
Deformed terraces along the shore of Yellowstone Lake and the
Yellowstone River record a complex history of
Holocene
deformation that has continued to the present. Based on studies of the terraces,
Hamilton (1985) proposed that intracaldera subsidence totaling more than 80 meters
occurred in stages during the early Holocene, and Meyer and Locke (1986) inferred
net uplift of about 10 meters in the northern Yellowstone Lake area
during the late Holocene. The latter authors also cited geomorphic evidence
that during the past several thousand years the lake fell to a level near the
present, rose 6-7 meters, fell to the present level or below, and now is rising
again to differential uplift of its outlet.
- Yellowstone Caldera
currently contains one of the largest and most active
hydrothermal systems
in the world, and hydrothermal activity probably has been relatively constant for at
least the past 10,000 years. The contemporary heat output of the Yellowstone
magmatic system is 4 x 10^16 cal/yr, or 5,500 MW
From: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.263-267, Contribution by R.L.Christiansen
-
The Yellowstone Plateau spans the continental divide between the
Northern and Middle Rocky Mountains, at an average elevation of around 2,400 meters.
The plateau lies at the center of one of the Earth's largest volcanic fields,
entirely post-dating 2.5 million years ago. The major eruptions of the
volcanic field were exceedingly voluminous, but their products are only
surficial expressions of the emplacement of a batholithic volume of rhyolitic
magma to high crustal levels in several episodes. The total volume of
magma erupted from the Yellowstone Plateau volcanic field
since 2.5 million years ago probably approaches 6,000 cubic kilometers.
-
This great magmatic volume and the enormous
calderas
produced by the largest pyroclastic eruptions are associated with a
surprisingly subtle morphology.
The Yellowstone caldera, the youngest of three nested and overlapping calderas,
is filled by younger rhyolitic lavas, and is readily recognizable in only one or two sectors.
The two older, nested calderas, however, form part of a conspicuous circular
basin at the west edge of the volcanic field, called Island Park
which is enclosed along its eastern margin by a younger constructional
lava platform at the west edge of the Yellowstone Plateau.
-
The Yellowstone Plateau volcanic field erupted a bimodal assemblage of
basalt and rhyolite in three cycles of activity. Each cycle began with eruptions
of both basalt and rhyolite; with time, the largest volume of rhyolite vented as
lavas from developing ring-fracture systems. The climax of each cycle was marked
by extremely rapid and voluminous eruptions of rhyolitic magma as
ash flows
from the ring-fracture system -- hundreds to thousands of cubic kilometers
being ejected in a few hours or days -- and by collapse of the source area to
form a large caldera. Post-collapse volcanism in each caldera has tended to fill it with rhyolitic lavas. Throughout each cycle of mainly rhyolitic volcanism, both basaltic and some rhyolitic lavas continued to erupt on the margins of the volcanic field, but no basalts erupted within the major active rhyolitic source are
as.
- The ash flows erupted at the climax of each cycle
form the three largely welded cooling units of the Yellowstone group, providing a framework for the
stratigraphy of the volcanic field. The 2,500-cubic-kilometer
Huckleberry Ridge Tuff erupted at 2 million years ago, the
280-cubic-kilometer
Mesa Falls Tuff at 1.3 million years ago, and the
1,000-cubic-kilometer
Lava Creek Tuff at 0.6 million years ago.
Each of these great eruptions
produced fallout ash deposits over large parts of the western United States,
leaving recognizable remnants as far east as the Mississippi River.
The first and third cycles were sustained by enormous bodies of rhyolitic
magma that accumulated to batholithic size, the highest parts of each intruding
and deforming its roof to form compound ring-fracture zones. When a major
eruption began from one of these high-level portions of the batholithic chamber,
the violent degassing triggered contemporaneous or successive eruptions from the
adjacent or overlapping ring-fracture zones, producing composite ash-flow sheets
and compound calderas that embrace the cluster of ring-fracture zones.
-
The compound caldera that formed during the climactic first-cycle Huckleberry Ridge eruption -- largest of the three -- spanned at
least 80 kilometers from
Island Park (at the margin of the basalt-covered Snake River Plain,
west of Yellowstone National Park), past the northern Teton Range
and Jackson Hole on the south, to the center
of the Yellowstone Plateau.
The second-cycle Henrys Fork caldera is the smallest of the three,
approximately 20 kilometers; both it and the surface outcrop of the
Mesa Falls Tuff are restricted to the Island Park area.
The third cycle began with the eruption of a series of voluminous
rhyolitic lavas from all sectors of a growing fracture system that embraced
two adjacent ring-fracture zones. The compound third-cycle Yellowstone caldera,
related to the Lava Creek Tuff eruption, is 70 x 40 kilometers
across in the center of the Yellowstone Plateau. The caldera is resurgent,
with an early post-collapse dome uplifted within each of its two segments,
followed by emplacement of early post-resurgence rhyolitic lavas from the
enclosing ring-fracture zones.
-
Renewed magmatic activity has produced voluminous lavas in the Yellowstone caldera since approximately 150 thousand years ago, perhaps even indicating
a fourth volcanic cycle. Following emplacement of a large rhyolitic lava
flow in the western ring-fracture zone, renewed uplift of the resurgent dome
occurred, reflecting insurgence of magma into the caldera system.
Since that time, voluminous rhyolitic lavas (several individual flows
exceeding 50 cubic kilometers) have filled the central part of the caldera
and overflowed its western rim. These lavas were emplaced in three major
episodes at approximately 150 thousand years ago, 110 thousand years ago,
and 70 thousand years ago, each time erupting from both the western and
eastern sides of the western ring-fracture zone to form the Madison
and Central plateaus, respectively. The aggregate volume of these
lavas is approximately 1,000 cubic kilometers. Deformation, probably
related to continued magmatic activity beneath the Yellowstone caldera,
continues with caldera-wide uplift and subsidence at rates as high as
2 centimeters per year. ...
-
The Yellowstone caldera region hosts the world's largest know
hydrothermal system,
highlighted by numerous geysers. This hydrothermal
system accounts for an average heat
flow from the caldera area 40 times greater than the global average.
Although the latest eruptions were approximately 70,000 years ago, the
immense hydrothermal system and a variety of geophysical characteristics
indicate that magma still underlies the Yellowstone caldera at a shallow depth.
A large negative gravity anomaly, low magnetic intensity,
high electrical conductivity,
shallow swarm seismicity, and large delays and high
attenuation of seismic waves are all
consistent with this inference.
-- Excerpt from USGS Yellowstone Volcano Observatory Website, 2002
-
The term supervolcano has no specifically defined scientific meaning. It was used by the
producers of a British TV program in 2000 to refer to volcanoes that have generated Earth's
largest volcanic eruptions. As such, a supervolcano would be one that has produced an
exceedingly large, catastrophic explosive eruption and a giant caldera. Because Yellowstone has
produced three such very large caldera-forming explosive eruptions in the past 2.1 million
years, the producers considered it to be a supervolcano.
Because there is no well-defined minimum size for a "supervolcano", there is no exact number of
such volcanoes. Examples of volcanoes that produced exceedingly voluminous pyroclastic
eruptions and formed large calderas in the past 2 million years would include Yellowstone, Long
Valley in eastern California, Toba in Indonesia, and Taupo in New Zealand. Other
"supervolcanoes" would likely include the large caldera volcanoes of Japan, Indonesia, Alaska
(e.g., Aniakchak, Emmons, Fisher), and other areas.
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01/22/03, Lyn Topinka