A VISIT TO YELLOWSTONE NATIONAL PARK-A GEOLOGIST'S PERSPECTIVE

 VISIT TO YELLOWSTONE NATIONAL  PARK USA-A GEOLOGIST’S PERSPECTIVE

C SATYANARAYANA                                                                                         

INTRODUCTION

The National Yellowstone Park is located in Wyoming,Montana and Idaho states of USA and situated in an vast area of 8983 Sq.Km. This park is famous for Wild Life, Geothermal features

and Sub-alpine forest.

Yellowstone Lake is one of the largest high elevation lakes and is centered over the Yellowstone 

Caldera or Craton the largest super volcano.

Yellowstone Park itself is a Volcano and one of its most spectacular eruptions occurred

640000 years ago. During the eruption, the land collapsed and left a large depression in 

the earth-the yellowstone Caldera or Crater. Within the past 2.1 million years three major

eruptions occurred in yellowstone and volcano is still active.

This Caldera filled with lava flows over hundreds of years creating the volcanic Plateau

that comprises much of the central part of the Park. Surprisingly, many of the Park’s Geysers

Hot springs,Mudpots and Fumaroles are also found near or within the Caldera.

Plate tectonics played an important role in the creation of Volcanic terrain in Yellowstone

Park. North America Plate and Pacific Plate collided along the western margin of North 

America. As the collision progressed North American Plate began to ride over the oceanic plate

which the oceanic plate was pushed down(Subducted) deep into the hot earth where it began to 

melt.This molten magma is the source for chain of Volcanoes.

Magma generated above the subducting slab(Pacific ocean plate) rose into North American

Continental crust about 300 to 500 Km. inland. Great arc-shaped volcanic mountain ranges grew  as lava and ash spewed out of dozens of individual volcanoes.                                                                                                                                                                                                                                                

North America plate scrapped against the top of the oceanic plate and peeled off layers of

Sediments. During the last half of Mesozoic Era, much of todays California,British Columbia,

Oregon and Washington were added to North America.

About 200 million years ago, the Plate motions adjusted,as the Pacific plate shifted to north

westerly course and shift transformed the head on collision to more of a glancing,sliding margin

became what is referred as the San Andreas Fault which includes many fault lands west of the 

San Andreas Fault system are part of Pacific plate those to the east belong to the North America.

THREE MAIN  LOCATIONS IN YELLOW STONE PARK

1 Noris Geyser Basin and Old Faithful

2 Mammoth Hot Springs

3 Mud Volcan

Before discussing above locations first let’s find out the meaning of Geyser,Hotspring,Mud volcano and Fumaroles.

Geyser- Geyser’s form if the fractures through which heated water flows contain constrictions.

Between eruptions, temperatures in the super heated pressurized water beneath the constriction buildup creating increasing amount of steam. Eventually, the steam pushes water

out of the constriction, water pressure deep in the system drops instantaneously and the Geyser

erupts. 

Hot Springs- Hot springs are features with no constriction unlike Geysers. Super heated water

cools slightly, as it reaches the surface and is replaced by hotter water from deeper source.This

sets up a pattern of water circulation which prevent the chain reaction leading to an eruption.

Fumaroles- (Steam vents) Hottest surface features. Their underground channel systems penetrate hot rock but are generally dry. When little water ( rain or melting snow) drain into the fumarole’s channel(fractures) converts instantly to steam and reaches the surface.

Mud Pots- Form when acid decomposes surrounding rock into clay.The clay mixes with water to form mud of varying consistency and color. Gas bubble burst through the mud and

 and create bubbles. 

1. NORIS GEYSER BASIN.

      2.1 million years old Caldera or Crator. Caldera is the place where volcanic eruption took 

place. It is acidic Geyser(PH is less than 5). It is one of the hottest and acidic Geyser in Yellow

Stone National Park’s hydrothermal area. Many hot springs and Fumaroles here have temperature
 near the boiling point(93 degree centigrade). Earth Quakes often changes the                                                                                                                           

features. Noris Geyser area is near the intersection of two major faults. One runs from the North

another runs from West. These two faults intersect with a ring fracture from the yellowstone Caldera eruption
 640000 years ago. Each year at Noris, new hot springs and geysers appear and others become dormant.

Geologic events trigger many of these changes. Even small earth quakes can alter hydrothermal behavior.
 Different colors found in Noris are evidence of thermophiles( heat loving microorganisms) and their activity

These colors are yellow-due to sulphur, Dark brown due to Iron Oxide, Emerald green due to chlorophyll

-a green pigment, Dark blackish green due to algae called Zygogonium

Geyser in Noris basin-    All of Yellowstone’s hydrothermal areas are heated by magma(partially molten rock)
 exist approximately 5 to 13 Kms below the earth’s surface in this area. Beneath  the Park, this partially molten magma

 heat water percolating down from the surface along fractures and faults. This superheated water rises back toward the
 surface collecting into larger channel focr each hydrothermal feature.

Old Faithful- Upper Geyser basin home of old faithful. The  majority of the world’s active Geyser’s are in the upper 
Geyser basin. Rangers forecast the eruption times of five Geysers here-

Old faithful

Castle Geyser

Grand Geyser

Daisy Geyser

River side Geyser

Within the past 2.1 million years, three major eruptions occurred in yellowstone and the 

volcano is still active. Partially molten rock or magma may be as close as 5-13Kms

underground. This magma produce first ingredient for thermal features. 

Second ingredient -water-Rain and Snow supply water. The water seeps down several thousand feet(one kilometer)
 below the surface where it is heated.Third ingredient-underground fractures(cracks)form third

 ingredient a natural plumbing system

Hot water rises through the plumbing (fractures) to produce Hotsprings if there is no constriction

in fractures and Geysers when there is constriction in fracture. In Geyser constriction in the fractures prevent
 water from circulating freely to the surface when heat would escape.

The deepest water can almost reach the boiling point of 93 degrees centigrade.

Pressurized water beneath the constriction buildup creating increasing amount of steam.

Eventually the steam pushes water out of constriction, water pressure deep in the system drops     

instantaneously  and the Geyser erupts.

The eruption stops when the reservoir is exhausted drained of water or heat. Old Faithful erupts more frequently than any of other big geysers although it is not the largest or most regular Geyser in the Park.Its average interval between eruption is about 90 minutes varying from 50-127 Minutes.                                       

 An eruption lasts 1.5 to 5 minutes expels(discharge)3700-8400 gallons(14000-32000 litres)of boiling water and reaches a height of 106-184 feet(32-56 meter). 

                                              

                                                     

                                                                                                                      

                                       

Hot Spring

Low Faithful Geyser

Low Faithful Geyser

                             

                                

2. Mammoth Hot Spring-

Terraces of Mammoth Hot Springs —At Mammoth, network of fractures and fissures form the 

plumbing systems that allows hot water from underground to reach the surface. The water comes  from rain and snow falling on the surrounding mountains and seeping deep into he earth where it is heated. Small earthquakes may keep the plumbing open.

Limestone occurs in the subsurface provides the final ingredient. Hot water(due to contact of percolated water with molten magma)with dissolved carbon dioxide makes a solution of weak carbonic acid. As the solution rises through rock  it dissolves calcium carbonate the primary compound in Limestone.

At the surface, the calcium carbonate is deposited in the form of travertine(is a form of Limestone deposited by mineral springs), the rock that forms the terraces of Mammoth Hot Springs. The Thermophiles(heat loving microorganisms)create tapestries of color where hot water flows among the terranes. Colorless and yellow thermophiles grow in the hottest water. orange,brown and green thermophiles thrive in cooler waters. Colors also changes with the seasons due to differing amount of sunlight.

The features are always changed, but the over all, activity of the entire area and the volume of water discharge  remain relatively constant.Different types of terraces existing in the Park.

Opal terrace

Main terrace

New high land terrace

white elephant back terrace

Angel terrace.

MAMMOTH TERRACES

 MAMMOTH TERRACES

 MAMMOTH TERRACES

                                  

 MAMMOTH TERRACES

    

GRAND CANYON OF THE YELLOWSTONE PARK

About 640000 years ago, a huge volcanic eruption occurred in Yellowstone park emptying a large underground chamber of Magma(partially molten rock). Volcanic ash spread for thousands of miles.

The roof of this chamber slowly collapsed forming a giant Caldera or Crator 45 Km across 75 Km long. The Caldera began to fill with lava flows continued for hundreds and thousands of  years. Scientists of the opinion that  the oldest Canyon of Yellowstone formed 160000 to 140000  year ago.This paleo crater was not as deep as the Canyon you see now.

Past and current hydrothermal activity weakened the Rhyolite(volcanic rock)lmaking the rocks softer. The yellowstone river eroded these weakened rocks to deepen and widen the Canyon a process that continues today. The current canyon begins at Lower  Falls and ends downstream from Tower falls.

The 308 feet(93m)lower falls may have formed because the river flows over volcanic rock more resistant to erosion than the downstream rocks which are hydrothermally altered. The 109 feet (33m) upper falls flows over similar rocks

The large rocks upstream from upper falls are remnants of a lava flows resistant to erosion.

The multi-hued rocks of the Canyon result from the hydrothermally altered rhyolite and sediments. The active hydrothermal features of colored rhyolites with dark orange brown and green areas near the river are seen. The Canyon can be viewed from south rim and 

north rim(in the map rims are shown).

WATER  FALLS IN CANYON

 RHYOLITE ALTERED DUE TO THERMAL WATERS AND GASES.

Waterfalls in RHYOLITE rock

   MUD VOLCANO-

 One of the most acidic features in the Park.Sulphur Caldron is located

here. The pungent odor of rotten egg is caused by hydrogen sulphide gas. Located near

the greatest uplift and sinking of the Caldera floor. Many faults converge here and Earth 

Quakes are common.

Here at mud volcano you are close to one of the resurgent domes. Resurgent domes are areas

of active ground deformation where the land moves up or down with the fluctuation of the magma chamber below. Scientists monitor these domes closely for information about ongoing       

volcanic activity.

                                                                                                                                                                                                                                                                                

The fascinating and mysterious mud features found here are some of the most acidic in the Park. This acidity plays a part in making them different from most hot springs and geysers.

Hydrogen sulphide gas is present deep in the earth at mud volcano.

Some microorganisms use the gas as an energy source. They help convert the gas to 

sulphuric acid which breaks down rock to clay. Listen to the sounds,notice the smell

and observing the colors of the mud volcano area. Much of what you sense comes from 

sulphur.

Dragon’s mouth springs has captured imaginations for centuries. In 1999, dramatic changes 

occurred. The water temperature dropped ten degrees and the color changed from green to 

chalky white.

MUD VOLCANO

MUD VOLCANO

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REFERENCES

1.TRAIL GUIDES OF NATIONAL PARK SERVICE

2.GEOLOGY OF USA-WIKIPEDIA.