MIDWAY GEYSER BASIN with GRAND PRISMATIC SPRING

Midway geyser basin seen alongside the Firehole river, is situated between the Upper and Lower
geysers basin . It is also home to one of the two largest geysers of Yellowstone National Park.
 In early days it  was  known as "Hell's Half Acre". The major geysers groups found  here 

are Excelsior geyser group,  Flood group and Rabbit creek group .

A hot spring is the result of geothermally heated ground water coming out through cracks in earth's

 surface. Unlike geysers which have obstruction resulting in their eruption, hot springs is 

unobstructed. It creates a cycle of hot water rising, cooling and falling . Flood Group and  Rabbit 

Creek group in Midway geyser basin  has no trails leading to it . This geyser basin have many
unnamed features . Flood group  consist of Flood geyser, circle pool  and West flood geyser.
  Egeria Springs and silent pool are the prominent ones in rabbit creek group.

Firehole River is a part of Missouri river system and is one of the two major tributaries of Madison 

river. It was named as firehole by early tappers due to steam rising from the water . It contain three of
Yellowstone's major waterfalls like Kepler cascades, Firehole falls and the Cascades of Firehole in Firehole canyon. 

The river  is surrounded by geothermal features which empty water into it resulting in high 

temperature of the river water. The river also contain dissolved chemicals and minerals from the
geothermal  features of Yellowstone. It is a fishing mecca and is famous for fly fishing. Brown trout
and Rainbow trout are mostly seen in this temperate water.

 In 1880's, Excelsior geyser was considered as one of  the largest geyser in the world . Due to the
violent eruptions, the internal plumbing system got damaged resulting in gas leakage and loss of
thermal energy. It is a productive thermal spring these days with a discharge of  around 4000 to 4500
 gallons of water per minute at a temperature of 199 degree Fahrenheit flowing directly into Firehole river.

 Last major eruption of Excelsior geyser was in 1985, reaching to a height of 300 ft. But due to
powerful eruptions its internal plumbing system got damaged and now it is seen only as a productive
 hot spring . Excelsior Group contain  Excelsior Geyser, Grand Prismatic Spring and Indigo
Spring. Numerous vents boil and churn the water within the crater and cover it in a dense layer of steam .

In June and July, purple fringed gentians are common here and bloom on the barren ground
surrounding this pool. This is also known as Rocky Mountain Fringed Gentian and is the official
flower of Yellowstone National Park. This  park flower  is also named  as Thermalis after the hotspring.

The Grand prismatic spring was first officially described by Ferdinand Heyden in 1871 , the leader of

 first federally funded exploration team of Yellowstone . According to him "Nothing ever conceived 

by human are could equal the peculiar vividness and delicacy of color of these remarkable prismatic

 springs. Life becomes a privilege and a blessing after one has seen and thoroughly felt these 

incomparable types of nature's cunning skill." . The most stunning view in the entire Yellowstone
National park is the Grand Prismatic Spring.

Grand prismatic spring has a diameter of 370 ft and depth of 121 ft . It discharges 2100 liters of hot 

water per minute. This is the largest hot spring in United Nation and third largest in the world.

 Frying Pan lake in  Zealand is the largest hot spring in the world followed by  Boiling lake in
Dominica.  Grand prismatic spring is named for its striking colors which match the rainbow 

dispersion of white light by an optical prism . 

The rainbow colors are the result of single celled pigmented microbial called Archae in the microbial

 mats, which grow around the mineral rich water. The amount of color depend on the chlorophyll to

 carotenoids and also based on temperature which favors one archae over another. During summer the

 prominent colors are orange and red while in winter they are dark green. The center of pool is blue 

and sterile due to extreme heat.

Opal pool at Midway geyser basin  is a fountain type geyser though behave as active hot spring.
Eruptions reach at a height of 30 ft to 70 ft. It is the largest active geyser at Midway geyser basin .
 It completely drained out in 2005 and  refilled as a vivid green pool in 2008.

Turquoise pool  is a pool with  milky white bottom and gem like blue colored water. The dissolved 

minerals add an opalescent iridescence. It maintains an underground connection with Excelsior 

geyser.It is evident when Excelsior is active, the water in Turquoise pool get lowered and took 

nearly an year to recover.

Many geysers here are ignored due to absence of trail system and limited visibility from the

road. The present  half mile boardwalk trail runs part way around the Grand Prismatic spring and 

past two much smaller pools (Opal and Turquoise) and to the adjacent crater of Excelsior Geyser.

In thermal areas the ground may be only a thin crust above  boiling hot spring or scalding mud. There

 is no way to guess a safe path as new hazards can bubble  up overnight. Hence it is always advised to

 stay on board walk

Camera : Canon t5