BACK  BASIN,

NORRIS  GEYSER  BASIN  (YELLOWSTONE  HOTSPOT)  HYDROTHERMAL  FEATURES

 

Norris Geyser Basin is the hottest of Yellowstone’s hydrothermal areas.  Much of the water discharged from Norris hot springs and geysers is slightly to strongly acidic.  The acid involved is H2SO4 - sulfuric acid.  Sulfuric acid forms as rising volcanic H2S gas (hydrogen sulfide - that’s responsible for the scent of rotten eggs) gets oxidized (H2S + 2O2 à H2SO4).  Sulfolobus microbes (Archaea, Mendosicutes, Crenarchaeota) are common at Norris Geyser Basin.  These microbes are thermoacidophiles - they love hot, acidic water - and they also oxidize hydrogen sulfide gas into sulfuric acid.

 

The high water temperatures at Norris Geyser Basin is a consequence of high subsurface heat flow.  This occurs because Norris Basin is above the intersection of multiple structures: the Hebgen Lake Fault Zone, the 640 ka Yellowstone Caldera rim fault, and the Norris-Mammoth Corridor Fault Zone.  A research well that was drilled in Norris Basin recorded a temperature of 459° F (= 237° C) at 1,087 feet depth.  Temperatures are even higher at greater depths.  Deep hot water reservoirs below Norris are estimated to be 640° F (= 340° C).

 

Norris Geyser Basin has three large concentrations of hydrothermal features located in somewhat broad, mostly siliceous sinter-floored, stream valleys.  These three hydrothermal areas are called the Back Basin, the Porcelain Basin, and the One Hundred Springs Plain.  Tantalus Creek and the South Fork of Tantalus Creek are the main drainage channels running through Back Basin - they capture geyser and hot spring runoff water.  The East Fork of Tantalus Creek drains Porcelain Basin.  Because of Norris Geyser Basin chemistry, Tantalus Creek water is acidic, chloride-rich, and sulfate-rich.  This water ultimately drains into the Gibbon River.

 

Norris Basin geyser and hot spring waters precipitate geyserite, also called siliceous sinter.  Geyserite is a chemical sedimentary rock composed of opaline silica (SiO2·nH2O - hydrous silica).  Most of Yellowstone’s hydrothermal areas have geyserite (a major exception is Mammoth Hot Springs, where travertine is commonly deposited, which is composed of calcite).  At Norris Geyer Basin, geyserite’s silica ultimately comes from rhyolitic ash-flow tuffs of the Lava Creek Tuff, which is the dominant bedrock unit in the area.  The Lava Creek Tuff is a 640,000 year old, lithified volcanic ash deposit.  It was emplaced immediately prior to the most recent Yellowstone Caldera collapse event.  Outcrops of Lava Creek Tuff in the Norris Geyser Basin area are frequently whitish-colored and acid-leached.

 

In most years, usually during late summer to early fall, Norris Geyser Basin undergoes basin-wide disturbances, during which the geysers, hot springs, fumaroles, and pools have unusual and/or energetic behavior.  The disturbances occur during times of lower water tables.  Less groundwater means lower pressures in the hot, deep reservoirs beneath Norris Basin.  Lower pressures result in more conversion of water to steam (boiling).  The excess rising steam plus boiling-induced mixing of different subsurface reservoir waters results in more energetic surface activity.  Disturbance activity is occasionally violent.  Hydrothermal explosions have occurred at Norris Basin during the park’s history - see the stories of Steamboat Geyser and Porkchop Geyser below.

 


 

Emerald Spring, northern Back Basin, central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~WSW).

This 25 to 30 feet deep pool has occasional geyser eruptions, but is usually a gently overflowing hot spring.  The water is acidic and near-boiling to superheated.  The intense green color is a combination of blue, colloidal silica-rich water (seen in many, very hot pools throughout Yellowstone) and yellow-colored elemental sulfur (S) lining the floor and walls of the pool.  A thin border of whitish-colored siliceous sinter, composed of opal (SiO2·nH2O - hydrous silica), encircles the pool.

A rising stream of bubbles near the center of Emerald Spring consists of water vapor (H2O), carbon dioxide (CO2), plus other gases.  A whitish- to grayish-colored, siliceous sinter-lined runoff channel heads southwest from Emerald Spring (see upper left of photo), merges with Monarch Geyser’s runoff channel, and eventually drains into Tantalus Creek.

In the early 1930s, Emerald Spring had significant and frequent geyser eruptions up to about 80 feet high.

During the annual Norris Geyser Basin disturbances, Emerald Spring becomes muddy (= suspended fine-grained sediments) and has relatively small geyser eruptions about 6 feet high or less.

 


 

Steamboat Geyser (above & below), northeastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Major eruptions at Steamboat Geyser are the tallest in the world.  This feature first appeared on 11 August 1878 after a hydrothermal explosion.  This was similar to, but larger than, the 5 September 1989 Porkchop Geyser hydrothermal explosion event (see below).  Steamboat Geyser consists of two vents in a gentle hillside of rhyolitic ash-flow tuff (Lava Creek Tuff, lower Middle Pleistocene, 640 ka).  Initially, the vents were powerful fumaroles that emitted steam and some mud.  By 1879, moderately high to high geyser eruptions occurred.  Small to large eruptions occurred at Steamboat Geyser from the late 1870s to the early 1910s.  This was followed by 50 years of dormancy.  Geyser eruptions resumed in the 1960s.  Dormancy occurred during the early and mid-1970s.  More major eruptions occurred in the early 1980s, followed by sporadic to rare events from the mid-1980s to the 2000s.

Major eruptions of Steamboat Geyser have fountains of water reaching over 100 feet high.  The highest have reached close to 400 feet high - the highest on Earth.  Major eruptions do not occur at regular intervals and thus are not predictable (decades ago, one woman waited 52 continuous days, hoping to witness a major eruption).  Steamboat’s major eruptions are about 3 to 40 minutes long, followed by hours of roaring fumarole activity.

Normal activity at Steamboat Geyser consists of frequent splashing spouts (see above & below photos) that reaching about 10 to even 60 feet high.  Emitted water at Steamboat Geyser is somewhat acidic and quite hot.

 

Steamboat Geyser (above & below), northeastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

 

Steamboat Geyser (above & below), northeastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

 

Steamboat Geyser (above & below), northeastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

 

Steamboat Geyser (above & below), northeastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Above (looking N): The runoff channel for Steamboat Geyser eruptions heads south and joins Tantalus Creek upstream from Tantalus Geyser).

Below (looking ~SSE): Steam plume from Steamboat Geyser, as seen from near Dr. Allen’s Paint Pots.

 

Steamboat Geyser in major eruption (looking N) during the 1960s (from frontispiece in White et al., 1988).

 


 

Sulphur Pot, eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

This small pool is located a little north-northwest of Echinus Geyser.  It has warm, nearly opaque, pale yellow-colored water that is quite acidic.

More than one feature labeled “Sulphur Pot” is shown on various Norris Back Basin maps.  One occurs a little east of Echinus Geyser and another (= the one shown above) occurs a little north-northwest of Echinus Geyser.

 


 

Black Pit Spring (above & below), eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA.

Above: 9 August 2011.  Below: 8 September 2005.

Black Pit Spring ranges from having inky-black water (see below) to greenish-gray, slightly murky water (see above).  This hillside feature was formerly several small fumaroles.  The pool contains hot, slightly acidic water.  The hillside consists of Upper Pleistocene glacial till.

 


 

Echinus Geyser (above & below), eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Above: looking ~SE.  Below: looking ~ESE.

Echinus Geyser is now mostly dormant but was formerly a frequently erupting geyser with high spouts, sometimes exceeding 100 feet.  The water at Echinus Geyser is acidic, hot, chloride-rich, and sulfate-rich, as are many hydrothermal features in Norris Geyser Basin.  Variations in water chemistry measurements indicate that this geyser erupts and discharges a mix of deep groundwater and shallow groundwater.

Spinose geyserite (siliceous sinter) is common at and immediately around Echinus Geyser, inspiring the name (“echinus” means “spiny”).  Chemical analyses of geyserite from here show that opaline silica (SiO2·nH2O - hydrous silica) is not the dominant material.  About 20% of the geyserite here is silica and about 57% is hematite (Fe2O3 - iron oxide), which is typically brick red to reddish-brown in color (note the reddish-brown color of the geyserite at the geyser and in the runoff channels in the above & below photos).  Other significant impurities in Echinus Geyser geyserite include arsenic, aluminum, sulfur, and calcium.  Whitish gray, low-impurity geyserite occurs below the surface, usually as irregular-shaped blocks.  Subfossil logs occur below that, dating to the early 1400s A.D.

At the surface, some geyserite rubble and blocks occur at Echinus Geyser.  These fragments were formed and deposited during violent geyser eruptions.  In the late 1970s, Echinus Geyser eruptions spewed small rock fragments composed of banded pyrite-marcasite (both are FeS2 - iron sulfide).  These sulfides have been observed in thin hydrothermal veins intruding geyserite in Echinus Geyser’s crater.

Pebbles of lithified rhyolitic ash-flow tuff litter the Echinus Geyser area, derived from adjacent hillside outcrops of Lava Creek Tuff (lower Middle Pleistocene, ~640 ka).  The geyserite rubble blocks and volcanic tuff pebbles have coatings of recent geyserite, often covered with spinose projections.

 

Echinus Geyser’s runoff channel (above & below), eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Above: hematite-rich, spiny geyserite in Echinus Geyser’s proximal runoff channel.

Below (looking west): Echinus Geyser’s runoff channel (center foreground) drains to the west and quickly merges with Tantalus Creek (= left side & distant center).

 

Echinus Geyser’s runoff channel, eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

 


 

Crater Spring (above & below), eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

This bluish-green pool is distinctive in having significantly projecting ledges of geyserite (siliceous sinter) (see the shadowed areas in the pool).  Some of these geyserite ledges collapsed long ago, resulting in scattered, angular geyserite blocks (see especially the left-center parts of the pool in the below photo).  The undercut geyserite ledges formed by erosive hydraulic action during energetic hydrothermal activity in former times.

In general, Crater Spring has been observed to be a small perpetual spouter.  Geyser activity occurred here in 1983 and 1984 with water spouting northward at an angle over 20 feet high.  More recently, it has been a relatively quiet pool.  The water here is very hot, acidic, chloride-rich, and sulfate-rich, as are many hydrothermal features in Norris Back Basin.

 


 

Root Pool, eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

This feature consists of two, water-filled, circular to irregular-outlined basins connected by a relatively narrow channel, and developed in Upper Pleistocene glacial till.  The water is slightly greenish-colored, slightly murky, acidic, and hot.  Small surface boils are present in both basins.  Root Pool has also experienced low splashing activity.  Geyser eruptions occurred here in late summer 1967.

 


 

Tantalus Geyser, eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~NE).

This geyser is referred to as Decker Geyser or Decker Island Geyser in the older literature.

Tantalus Geyer’s vent occurs in the channel of Tantalus Creek, and so all of the stream’s drainage enters and exits the pool.  This geyser is normally quiet, but it splashes and becomes turbid during the annual Norris Geyser Basin disturbances.

In 1969, activity at Tantalus Geyser included spouts of brown, turbid water up to 35 feet high.

 


 

Arch Steam Vent (above & below), eastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Arch Steam Vent is an active fumarole with an irregularly slit-shaped vent developed on a hillside of rhyolitic ash-flow tuff (Lava Creek Tuff, member B, lower Middle Pleistocene, ~640 ka), glacial till (Upper Pleistocene), and geyserite (siliceous sinter).

This feature formerly had an arch of geyserite, which has since collapsed.  Geyserite arches are very rare, but an intact example still exists at Avoca Spring in the Sapphire Group at Biscuit Basin.

Rarely, this feature discharges acidic, chloride-rich, and sulfate-rich water in the form of runoff and angled geyser eruptions up to an estimated 40 feet high.

 


 

NBBNN25, (above & below), east-central Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

This unnamed hydrothermal feature is just west of Arch Steam Vent.  It consists of a small, bubbling pool adjacent to two larger ponds.  NBBNN25 has acidic, low-temperature water.  The medium gray-colored materials lining the walls of the pool appear to be stratified glacial deposits.  The light-colored gravel surrounding the pool is weathered geyserite (siliceous sinter).

 


 

Dishwater Spring (above & below), east-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Above: looking ~SSW.  Below: looking ~E.

Dishwater Spring is a subcircular, slightly bubbling pool perched above a larger pond having an irregular outline.  The symmetrical mound immediately surrounding the spring is composed of geyserite and weathered geyserite.  Dishwater Spring occasionally overflows (see the whitish-yellow runoff channel on the right side of all three photos above & below).  The pool’s water is hot, somewhat acidic, and chloride-rich & sulfate-rich.

 

Dishwater Spring, east-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~E).

 


 

Mystic Spring (above & below), south-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA (looking ~NW).

Above: 9 August 2011.  Below: 8 September 2005.

Mystic Spring is an irregularly circular pool located between Dishwater Spring (see above) and Mud Pool (see below).  It is surrounded by geyserite, weathered geyserite, and geyserite gravel.  The subaqeous portions of the pool’s geyserite have a pale yellowish-colored coating of elemental sulfur.

The behavior of this feature varies.  It ranges from being fairly quiet to gentle boiling to overflowing to perpetual splashing.  During some annual basin-wide disturbance events, Mystic Spring has geyser eruptions.  During the mid-2000s, eruptions reached 4 feet high.

Water here is moderately hot and quite acidic.

 


 

Mud Pool (Mud Spring), southern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA (looking ~NW).

Above: 9 August 2011.  Below: 8 September 2005.

Mud Pool can have clear, blue water or slightly turbid, greenish water or very muddy water.  Water turbidity (= high abundance of suspended, fine-grained sediments) usually occurs here during the annual basin-wide disturbances.  The water is quite hot and acidic, as are many Norris Back Basin features.

During occasional years, Mud Pool has geyser eruptions.  Many are low surging eruptions while others reach up to 30 feet high.

 


 

NBBNN04 (above & below), southern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Above: looking ~WNW.  Below: looking ~W.

This unnamed hot spring pool contains hot, acidic water.

 


 

Yellow Mud Pool, southern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~WSW).

The small, dark greenish gray to black pool in the right-center foreground appears to be the feature that has been called Yellow Mud Pool.  Its water is cool and very acidic.

 


 

Puff 'n Stuff Geyser (above & below), southern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SE).

Puff 'n Stuff Geyser frequently acts as a fumarole or sprayer.  Rare geyser eruptions also occur that reach about ten feet high.  Puff 'n Stuff’s water is very hot and fairly acidic.

 


 

Black Hermit Cauldron, southern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SSW).

This acid hot spring consists of two overlapping craters, usually filled or nearly filled with hot to very hot water.  Observed behaviors include light bubbling-boiling action, heavy boiling, overflowing, surging, and small, splashy bursting.  The water is usually opaque and ranges from pale blue to grayish to gray-brown to dark gray to black.

A steep hillside composed of Upper Pleistocene glacial till occurs on the southern side of Black Hermit Cauldron.  The flats on the northern and northeastern sides of the spring consist of the same till, plus Upper Pleistocene disrupted kame deposits.

 


 

Green Dragon Spring, southern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~ESE).

At Green Dragon Spring, water emerges from three water-filled basins that form one larger pool having an irregularly elongated outline.  The easternmost of these three basins occurs in a “cave”, under an overhang of lithified Upper Pleistocene disrupted kame deposits.  The walls and ceiling of the “cave” are yellowish, greenish, and orangish in places, which can be difficult to see in the shadows and rising steam.  The colored areas represent coatings of elemental sulfur and iron sulfates.

The hot to boiling-hot, acidic water emerging at Green Dragon Spring appears to be derived via subsurface conduits or subsurface diffuse flow from Gray Lakes, immediately west of here (see below).  Green Dragon Spring’s water drains westward, back to Gray Lakes.

Water at Green Dragon Spring is often deep green and slightly murky.  During the annual Norris Geyser Basin disturbances, water here becomes muddy brown (= high abundance of suspended, fine-grained sediments).

 


 

Gray Lakes, southwestern Back Basin, southwestern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SW).

The Gray Lakes consist of two moderately large ponds in the headwaters area of the South Fork of Tantalus Creek.  The water is usually turbid (muddy), bluish-gray to grayish-green in color, hot, acidic, chloride-rich, and sulfate-rich.  Many springs occur along the borders of the Gray Lakes; these springs discharge much water into the lakes, which is then discharged into the north-flowing South Fork of Tantalus Creek.  Some of these bordering springs have occasional geyser eruptions.

 


 

South Fork of Tantalus Creek, southwestern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on on 9 August 2011 (looking ~S).

The South Fork of Tantalus Creek flows north and drains the Gray Lakes area of Norris Back Basin.  The water is warm to hot, acidic, chloride-rich, and sulfate-rich.  The green coloration in the channel on the left is from colonies of unicellular, photosynthetic, extremophile organisms - Cyanidium caldarium in this case.  Confusingly, despite its green color, Cyanidium caldarium is a red alga (Rhodophyta, Rhodophyceae, Cyanidiales, Cyanidiaceae).  This genus of red algae is known to prefer hot, acidic water environments.

The hill in the distance is composed of rhyolitic ash-flow tuff of the Lava Creek Tuff (lower Middle Pleistocene, 640 ka) and covered by Upper Pleistocene glacial till.

 


 

Blue Mud Spring (above & below), southwestern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~W).

Blue Mud Spring is one of my favorite features in Norris Geyser Basin.  It can be a fumarole or a muddy, splashing perpetual spouter or an overflowing hot spring.  It’s also had muddy mist eruptions up to 10 feet high.  Blue Mud Spring water is very hot and somewhat acidic.

 

Blue Mud Spring (above & below), southwestern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

 


 

Yellow Funnel Spring, southwestern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~NE).

Yellow Funnel Spring has a subcircular, fairly symmetrical, funnel-shaped basin.  This feature has varied significantly in its appearance over the decades.  It was formerly was an attractive, multicolored, relatively quiet, water-filled pool.  It had pale bluish-green water at the center and was surrounded by yellow, sulfur-coated geyserite.  The yellow sulfur areas were surrounded by geyserite coated with/stained by pale orangish-brown iron sulfate and purplish-gray iron sulfate.

In recent decades, Yellow Funnel Spring’s turbidity (= muddiness) was frequently high.  Many times, the spring’s basin has been dry, or barely filled with water.  Geyser eruptions have occurred here, involving spouts between 1 and 6 feet high.  During the 2000s, geyser eruptions at Yellow Funnel Spring eroded its own basin (see the jagged-shaped walls in the lower parts of the pit in the above photo).

The sloping walls of Yellow Funnel Spring’s basin are Upper Pleistocene glacial deposits, interpreted by some as glacial till, but identified by others as disrupted kame deposits.  A thin crust of geyserite caps the glacial material (see the back right-hand side of the basin in the above photo).

Water at Yellow Funnel Spring is hot to near-boiling and acidic.

 


 

 

Porkchop Geyser (above & below), western Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA.

Above: pre-1989 appearance of Porkchop Geyser’s vent area (from National Park Service trailside signage).

Porkchop Geyser was formerly known as Porkchop Spring.  It’s basin was shallow, had a porkchop-shaped outline, a pustulose geyserite border, and a very small vent (see above and below).  Occasional to regular geyser eruptions occurred here during the 1970s and 1980s; spouts reached up to about 20 feet high.  From 1985 to mid-1989, Porkchop exhibited perpetual spouter behavior, with a roaring column of water reaching over 30 feet high.

On 5 September 1989, during the annual basin-wide disturbance, a hydrothermal explosion event occurred at Porkchop Geyser, the first one in Norris Back Basin since the large 1878 event that created Steamboat Geyser (see above).  The explosion was immediately preceded by partial collapse of Porkchop Geyser’s very small vent, resulting in a brief, high geyser eruption, reaching to about 100 feet.  This abnormal discharge of water lowered pressure in Porkchop Geyser’s subsurface reservoir.  The lowered pressure caused a large volume of superheated reservoir water to instantly boil and convert to steam.  The steam pressure was sufficiently high to explosively shatter geyserite around the vent and send large to small rock fragments up to 220 feet away (one rock was roughly 6 by 4 by 2.5 feet in size).  Angular geyserite boulders and smaller rubble still surround the vent to this day.  Geologists who examined the site a few hours after the explosion found some geyserite (= hydrothermal opal - hydrous silica) that was soft and gelatinous; this material was derived from the pre-explosion subsurface conduit walls.

Since the explosion, the feature has been a hot spring with milky blue-colored water and having gentle surface disruptions by rising gases.  Occasional geyser eruptions have occurred here since 1989.

Water at Porkchop Geyser ranges from slightly hot to very hot.  Unlike many Norris Back Basin features, Porkchop Geyser water is not acidic - it’s usually close to neutral or slightly alkaline.

Below: pre-1989 appearance of Porkchop Geyser’s vent area (from National Park Service trailside signage).  The photo on the left shows perpetual spouter activity in 1986.  The photo on the right shows the very small vent (shadowed) - it was about 1 to 2 inches in size.

 

 

Porkchop Geyser (above & below), western Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA.

Above: pre-1989 eruption of Porkchop Geyser (from National Park Service trailside signage).

Below: post-explosion appearance of Porkchop Geyser with abundant bedded geyserite boulders and finer-grained rubble formed and deposited during the 1989 hydrothermal explosion event (from National Park Service trailside signage).

 

Porkchop Geyser (above & below), western Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Hydrothermal explosion-generated geyserite rubble surrounds a milky blue-colored pool.  The coloration is caused by an abundance of suspended, submicron-sized colloidal silica plus larger particles of suspended solid silica.  Without the latter, the water would be clear blue (see, for example, Sapphire Pool in Biscuit Basin and Gem Pool in the Cascade Group).  With the addition of suspended solid silica, hot spring water becomes milky blue.

 


 

Pearl Geyser (above & below), western Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~WNW).

Pearl Geyser is an attractive, subcircular-shaped feature located east-northeast of Porkchop Geyser.  Over the decades, Pearl Geyser has variously been an empty fumarole, partially water-filled, and completely water-filled.  It can be an overflowing hot spring, it can have frequent small splashing activity, and it can have geyser eruptions.

In the past, Pearl Geyser had clear blue water.  The photos above & below show milky blue water, the result of suspended, submicron-sized colloidal silica particles plus larger particles of suspended solid silica.  The hot spring water has deposited cream- to tan-colored geyserite in most of the crater, surrounded by a ring of gray to dark gray geyserite

Water at Pearl Geyser is hot to near-boiling and ranges from being slightly acidic to neutral to slightly alkaline.

 


 

Vixen Geyser (above & below), northwest-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~NE).

Vixen Geyser is located to the north-northeast of Pearl Geyser.  The relatively small vent is surrounded by light gray, blocky-weathering geyserite (siliceous sinter).  The vent has reddish-brown staining from deposition the iron oxides hematite and limonite.

Geyser eruption durations here range from seconds to almost an hour long.  Eruption fountain heights vary, but reach up to 40 feet high.  Water at Vixen Geyser is quite acidic and hot to boiling hot.

Vixen Geyser may originally have had a prominent, multivent, spinose geyserite cone.  A Yellowstone geyserite cone having that description is on display at America’s National Museum of Natural History (= Smithsonian Institute; = United States National Museum) in Washington D.C.  The museum’s specimen was collected and shipped by an early park superintendent.  Unfortunately, available historical evidence is ambiguous and contradictory.  Some written records indicate that the Smithsonian specimen is definitely not from Vixen Geyser.  Other reports suggest that it might indeed be from Vixen Geyser in Norris Back Basin.  I strongly suspect that the Smithsonian specimen is not from Vixen, but Vixen’s present vent area “looks” slightly unnatural, as if something is missing.  It’s possible that more than one geyserite cone was collected by early park officials.

 


 

Tantalus Creek, north-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~NW).

Tantalus Creek is the main drainage in Norris Back Basin.  Here, it is flowing to the northwest; it joins with the South Fork of Tantalus Creek in the distance.  Much of the water in these creeks is geyser and hot spring runoff.  Chemically, the creek water is acidic, chloride-rich, and sulfate-rich.

 


 

Corporal Geyser, north-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Corporal Geyser is a circular pool lined and walled by geyserite (siliceous sinter).  An overhanging ledge of geyserite occurs in the northwestern portion of the pool.  The water is acidic and hot.  This feature can be dormant or occasionally overflowing or having small splashing geyser eruptions.

 


 

Dog’s Leg Spring (above & below), north-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Located next to Corporal Geyser, this small hydrothermal feature’s activity was first observed in the 1970s.  The two vents are surrounded by geyserite (siliceous sinter) and Upper Pleistocene glacial till.  Geyserite pebbles and finer-grained sediments, plus plant debris partially fill the vents.  Dog’s Leg Spring water is acidic and hot to very hot.  Geyser eruptions are moderately small, and reach about 3 feet high.

 

Dog’s Leg Spring (above & below), north-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Above: eastern vent.  Below: western vent.

 


 

Veteran Geyser (above & below), north-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SSW).

This multivent geyser consists of a moderately large central crater walled by whitish-gray geyserite (siliceous sinter) that is overhanging in places.  Just to the south of the crater is a moderately small vent (the “main vent”), surrounded by pale yellowish- to cream-colored geyserite.  Most eruptive activity occurs there.  Small splashing eruptions are nearly perpetual.  Some geyser spouts here reach 50 feet high.  The central crater fills with water during episodes of significant geyser activity.

Another vent (see first photo below) occurs below an eroded, overhanging geyserite ledge outside the northwestern margin of the central crater.  When active, that vent ejects water at a low angle.

Veteran Geyser water is essentially neutral to slightly acidic and near-boiling hot.

 

Veteran Geyser (above & below), north-central Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

 

Veteran Geyser, north-central Back Basin, southern  Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

 

Veteran Geyser, north-central Back Basin, southern  Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

This knob of pustulose to spiny geyserite (siliceous sinter) is adjacent to the vent under the overhang along the northwestern outside margin of Veteran Geyser.

 


 

Veteran’s Auxiliary Vent, northern Back Basin, southern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SE).

Activity at Veteran’s Auxiliary Vent typically consists of rises in water level.  These occur at the same time as activity at adjacent Veteran Geyser.  Water levels here are usually subsurface.

 


 

Cistern Spring (above & below), northeastern Back Basin, southeastern Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011.

Above: looking ~ESE.  Below: looking ~SSE.

Cistern Spring’s summer 2011 appearance is nearly identical to Emerald Spring (see above).  Before the mid-1960s, Cistern Spring was a quiet, dark-colored hot spring.  It then transformed into a boiling, overflowing, milky blue-colored hot spring.  The silica-rich runoff started rapid buildup of geyserite around the pool.  It also started killing the evergreen trees in the surrounding forest (see above & below photos).

The subsurface reservoir and underground plumbing system of Cistern Spring are connected with nearby Steamboat Geyser, the tallest erupting geyser on Earth.  Activity at Cistern Spring doesn’t precede Steamboat Geyser activity, so it can’t be used to make predictions.  But Cistern Spring does have obvious responses to Steamboat activity, particularly its famous major eruptions.  Steamboat major eruptions result in Cistern Spring’s pool displaying unusual activity, such as decrease in water level, increase in turbidity (muddiness - suspended, fine-grained sediments), and cooling of its surface water.  Sometimes, Cistern Spring has had surging overflow or geyser eruptions about 20 feet high in response to Steamboat activity.

In summer 2011, Cistern Spring was not a blue-colored pool.  It had a green coloration, the result of mixing of “blue water” with the yellow-colored coatings of elemental sulfur on the floor and walls of the pool.

Cistern Spring water varies in temperature and acidity.  It ranges from moderately hot to very hot.  It can be somewhat acidic to neutral to very slightly alkaline.

 


 

Palpitator Spring (Palpitator Geyser) (above & below), northern Back Basin, south-central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~W).

This moderately small, relatively shallow, circular hot spring has small surging domes at its surface, causes by rising gases.  These surges generate radiating ripples and cause bouncing water levels.  Slightly overflowing water occurs sometimes, which drains to the west (see the runoff channel on the far side of the pool in the above & below photos) and empties into Tantalus Creek.

Small splashing geyser eruptions occur at Palpitator Spring and reach about 3 feet high.  Stronger eruptions were reported here in the late 1800s.

Water at Palpitator Spring is hot and close to neutral (not acidic or alkaline).  The spring is surounded by light gray-brown to whitish gray geyserite (siliceous siner).

 


 

Fearless Geyser (above & below), northern Back Basin, south-central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~NW).

Fearless Geyser is located just northeast of Palpitator Spring.  It is a dark, moderately small, circular pool over 20 feet deep with slightly acidic water that is hot to superheated.

Boiling surges occur near the center of the pool, sometimes doming to about 1 foot high.  Geyser eruptions occurred here in the past, reaching over 25 feet high.

Weathered geyserite gravel and finer grains surround Fearless Geyser’s pool.  The vent itself is walled by spinose geyserite.

 

Fearless Geyser, northern Back Basin, south-central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~NW).

 


 

Monarch Geyser, northern Back Basin, southwest-central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~E).

Many decades ago, Monarch Geyser was the 2nd most significant geyser in Norris Back Basin (Steamboat Geyser is # 1).  In the late 1800s, Monarch erupted periodically and powerfully up to 200 feet high.  This activity stopped in the early 1910s.  Before it ceased activity, eruption columns from Monarch were observed to be dark-colored (muddy; sediment-rich), indicating subsurface conduit erosion.  Such conduit erosion usually indicates that the ability to have additional geyser eruptions is diminished.  Since 1913, Monarch has had no activity, except for sporadic activity during a few years in the 1920s, plus geyser eruptions up to 20 feet high from 1994 to 1996.

Monarch Geyser is located in a subcircular amphitheater with partially vegetated sloping walls.  The walls expose rhyolitic ash-flow tuff of the Lava Creek Tuff (lower Middle Pleistocene, 640 ka).  The amphitheater, or alcove, was presumably eroded through the volcanic tuff by the energetic hydrothermal activity of Monarch Geyser.  It’s possible that this feature originated via a hydrothermal explosion event, similar to the explosions at Steamboat Geyser in 1878 and Porkchop Geyser in 1989.

Monarch Geyser’s irregularly-shaped pool has clear, green to pale-green water similar to Emerald Spring and Cistern Spring (see above).  The water is hot, somewhat acidic, chloride-rich, and sulfate-rich.  Its modern activity consists of overflow, plus minor surface disturbances and boils.

 


 

Branch Spring, northern Back Basin, southwest-central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SW).

Branch Spring is a slightly bubbling pool of hot, acidic, nearly-clear, pale yellowish-green water.  Overflowing water drains to the southwest, merges with Monarch Geyser’s runoff channel, and then drains into Tantalus Creek.

 


 

Minute Geyser, northern Back Basin, southwest-central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SW).

This is no longer a “natural” feature.  Morons and boneheads over the decades have significantly vandalized this geyser.  It formerly had very frequent eruptions (hence the name).  Anti-nature jerks have thrown innumerable rocks into Minute Geyser’s vent basin (compare this with the thousands of coins and other trash thrown into Morning Glory Pool in Yellowstone’s Upper Geyser Basin).  Some of these rocks were removed in the 1930s, but more rocks were later thrown in.  The vent is basically sealed up now - geyserite has cemented the rocks together.

Minute Geyser has two vents - the larger main vent has been wrecked.  The smaller vent’s activity includes small to medium-sized geyser eruptions.  In the early 20th century, some Minute Geyser eruptions reached about 80 feet high.

Water here is almost neutral to very slightly alkaline and is hot to very hot.

 


 

Forgotten Fumarole, northern Back Basin, central Norris Geyser Basin, Yellowstone Hotspot, northwestern Wyoming, USA on 9 August 2011 (looking ~SW).

This feature usually acts as a fumarole (steam vent), but geyser eruptions occurred during the 2000s, some up to 30 feet high.  The vent is surrounded by weathered, whitish-gray, irregularly layered to blocky geyserite (apparently including cemented geyserite rubble).

 


 

Info. mostly synthesized from:

 

Bryan, T.S.  2008.  The Geysers of Yellowstone, Fourth Edition.  Boulder, Colorado.  University Press of Colorado.  462 pp.

 

Christiansen, R.L. & R.A. Hutchinson.  1987.  Rhyolite-basalt volcanism of the Yellowstone Plateau and hydrothermal activity of Yellowstone National Park, Wyoming.  pp. 165-172 in  Geological Society of America Centennial Field Guide Volume 2 - Rocky Mountain Section.  Boulder, Colorado.  Geological Society of America.

 

Dyer, B.D.  2003.  A Field Guide to Bacteria.  Ithaca, New York.  Cornell University Press.  355 pp.

 

Hendrix, M.S.  2011.  Geology Underfoot in Yellowstone Country.  Missoula, Montana.  Mountain Press Publishing Company.  302 pp.

 

Margulis, L. & K.V. Schwartz.  1998.  Five Kingdoms, an Illustrated Guide to the Phyla of Life on Earth.  New York City.  W.H. Freeman and Company.  520 pp.

 

Paperiello, R.  1985.  Report on the Norris Geyser Basin for 1984.  286 pp.

 

Schreier, C.  1987.  A Field Guide to Yellowstone’s Geysers, Hot Springs and Fumaroles.  Moose, Wyoming.  Homestead Publishing.  96 pp.

 

United States Geological Survey - 1990s to 2000s geochemistry data set.

 

White, D.E., R.A. Hutchinson & T.E.C. Keith.  1988.  The geology and remarkable activity of Norris Geyser Basin, Yellowstone National Park, Wyoming.  United States Geological Survey Professional Paper 1456.  84 pp.  1 pl.

 

Yellowstone Association.  2011.  Norris Geyser Basin Trail Guide.  [12] pp.

 

Yellowstone National Park’s Research Coordination Network - 1998 geochemistry data set.

 


 

 

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