VOLCANIC
SPRINGS

Mammoth Hot Springs, Lower Terraces - page 2

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From the level of Minerva Terrace stairs climb up to the level of Main Terrace and beyond, where the trail runs along the elevated, eastern rim of a travertine terrace called The Esplanade. It is named for the panoramic view over Main-, Jupiter- and Mound Terrace and continues (without trail) northwestward to tower over Minerva Terrace, too. The Esplanade has no historical record of flowing thermal water and is regarded as part of Prospect Terrace, the next higher level on Terrace Mountain. Looking down on the lower terraces' northwest corner, pools and terracettes of New Blue Spring catch the eye.

New Blue Spring Mammoth Hot Springs Yellowstone
New Blue Spring, terracettes in July 2011

Actually, New Blue Spring consists of several different vents, and the position of the pool shifts from time to time accordingly. The original Blue Spring, described by the Hayden expedition in 1872, was located more or less at the same position of the current New Blue Springs. But the original one ceased flowing in 1889, and another spring near the center of Main Terrace was named Blue Spring instead. Later springs at the former position sprang into life and they were called New Blue Springs. Up until 2005 New Blue Spring flowed high volumes of thermal water, cascading down the brink and continuously forming or extending terracettes. But thereafter the discharge dropped and the water has been confined to some smaller pools on top level only. The next picture shows a spring located near the boundary to Jupiter Terrace. In most years this spring is empty.

New Blue Spring Mammoth Hot Springs Yellowstone
One of the New Blue Springs near the boundary to Jupiter Terrace (August 2017)

Southwest of the New Blue Springs one of the dry vents of Summit Basin Spring is still visible. This spring had ceased flowing in 1872 and became a top attraction when its two large pools refilled in 1936. In his New Guide from 1936 Jack E. Haynes wrote: "Jupiter Terrace Parking Area (Mileage 6.5) affords a splendid view of Summit Basin Spring." However, the excitement was short-lived because the spring already dried up again at the end of 1937. Although at that time the name Summit Basin Spring had been officially used in the superintendents' reports, the sign at the current overlook directly in front of the old vent, reading "New Blue Spring", seems to allocate it now to the New Blue Springs.

Summit Basin Spring Mammoth Hot Springs Yellowstone
Dry vent of Summit Basin Spring (on righthand side) in 2011. Mt. Everts in background

The boardwalk proceeds along The Esplanade and passes Cupid Spring, which is likewise part of the higher Prospect Terrace. Cupid Spring was firstly observed in 1931 and its last noteworthy period of activity ceased in the 1990s. From 2010 onwards, Cupid Spring showed new discharge, which is getting stronger from year to year.

Cupid Spring, Mammoth Hot Springs
Cupid Spring in August 2017 (roll mouse over picture for comparison with July 2013)

South of Cupid Spring the old boardwalk (up until 2014) curved east around Trail Spring. Located at the southwest corner of Main Terrace, it came into existence in 1962 and has been intermittently active since then. As already seen before with other springs, over the time different vents may emerge. The vents, which were active from 2007 to 2013, are called New Trail Spring.

New Trail Spring Mammoth Hot Springs Yellowstone
New Trail Spring in July 2011

The contrast between the petrified ground and interspersed tree skeletons is the signature feature of New Trail Spring.

New Trail Spring Mammoth Hot Springs Yellowstone
New Trail Spring, terracettes in July 2011 (location of vent in background left)

2013 was the most recent year so far when New Trail Spring displayed water.

New Trail Spring Mammoth Hot Springs Yellowstone
New Trail Spring, last active vent in July 2013

Across the old boardwalk from New Trail Spring, Grassy Spring has developed a remarkable travertine bed since it has emerged in 2008. Eventually, in 2014, the boardwalk had to be shifted to the west upslope of Grassy Spring's vent to prevent any interference with the natural travertine deposition process.

Grassy Spring Mammoth Hot Springs Yellowstone
Grassy Spring in July 2013, seen from the old boardwalk

As a newly emerged spring literally on a green field, Grassy Spring impressively illustrates the process of terrace formation from the earliest stages on. Starting from the currently existing micro terracettes, the rising new terrace will develop terracettes with successively deeper ponds, and on the long term overhanging terracette deposits, if activity continues long enough.

Grassy Spring Mammoth Hot Springs Yellowstone
Grassy Spring in August 2015, seen from the new boardwalk

The new boardwalk above Grassy Spring also passes a cavity, which was almost completely obscured before. This is an example of a solution cave (a cave eroded by cooled down spring water or rainwater) in the limestone of Mammoth Hot Springs, but it is only a small one. Larger caves, such as the Stygian Caves (encompassing Stygian Cave, Stalactic Cave and Hermit’s Cave), Poison Cave, and the Devil's Kitchen are located in the Upper Terraces Area, while McCartney's Cave is to be found on Hotel Terrace. To none of the caves access is permitted any longer, not even to the area of their entrance. The Devil's Kitchen had been open to visitors until 1939, but then it was closed due to an unpredictably changing carbon dioxide concentration in the air and lack of oxygen. Repeatedly, huge numbers of animals, mostly birds, were found dead inside the caves due to poisoning by carbon dioxide.

Cave at Mammoth Hot Springs Yellowstone
Cavern close to Grassy Spring in 2015

Dryad Spring, a short distance farther east, underwent a similar development over nearly the same period of time as Grassy Spring.

Dryad Spring Mammoth Hot Springs Yellowstone
Dryad Spring runoff in July 2013

Since the 1870s Canary Spring, named after its canary bird yellow color, has been intermittently active and often was one of the stars of Mammoth Hot Springs. Its water formed beautiful terracettes on the steep slope at the southeast corner of Main Terrace. Unfortunately, as had been observed several times in the past, since 2012 the discharge of Canary Spring once again has declined dramatically.

Canary Spring Mammoth Hot Springs Yellowstone
Canary Spring, pool on top of Main Terrace in July 2011

Canary Spring Mammoth Hot Springs Yellowstone
Canary Spring, terracettes in July 2011

In 2013 the pool of Canary Spring shrunk to small ponds around the vent, and the runoff over the brink of Main Terrace ceased. During the same time a spring farther north, beyond Canary Spring, has amplified its activity considerably. In the strict sense this waterbody is fed by vents in the perimeter of the Main Springs. However, the entrenched name Canary Spring persisted, not least because of the sign attached to the handrail.

Canary Spring Mammoth Hot Springs Yellowstone
Drying vent of "old" Canary Spring in foreground, "new" Canary Spring / Main Spring in background (July 2013)

It seems as if the activity of the "old" Canary Spring shifted northwards. There, a series of widely protruding, awesome terracettes rose in a short time. The disadvantage for visitors is, however, that the spectacle takes place at a distinctly larger distance to the boardwalk compared to the old Canary runoff.

Canary Spring, Mammoth Hot Springs
Terracettes of "new" Canary Spring in July 2013 (roll mouse over picture for comparison with same edge in August 2015)

Canary Spring Mammoth Hot Springs Yellowstone
"New" Canary Spring's upper terracettes, view down from above in August 2017

After the thermal water has dropped over the brink it cascades down the slope and builds up terracettes which resemble open, filled barrels. This east slope of Main Terrace is called Marble Terrace.

Canary Spring Mammoth Hot Springs Yellowstone
"New" Canary Spring's lower terracettes on Marble Terrace in July 2013

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