Tuesday, July 9, 2013

Photo-Essay and Geo-history: Yellowstone National Park. Part I

Excelsior Geyser

From the time of our earliest stories, mountains have held a prominent place in our collective imaginations. Myths and legends from around the world feature mountains, especially the volcanic kind as the locus of our creation-stories. From the Greeks whose gods lived high on Mount Olympus, to the legends of Pele, the fire-goddess of Hawai’ian volcanoes, these geographical elevations have occupied our attentions in every aspect of our lives – in literature, in art, in our attempts at pushing the boundaries of physical endurance, in explorations -scientific and otherwise, and in our religions. Our affinity for the mountains has not been diminished by their volcanic eruptions. On the contrary, these violent outbursts have only added to their allure by feeding our sense of awe. The following is a photo-essay and geo-history of the volcanic caldera that we call Yellowstone National Park.
Yellowstone National Park has the singular distinction of being the world’s and America’s first national park. What is it about Yellowstone’s landscape that generated, for the first time in world history, the desire to ‘preserve’ in an official capacity? And what historical events led to president Ulysses Grant declaring, on March 1st, 1872, Yellowstone National Park as a nature preserve? Some answers, verbal and photographic:
Part I explores the geo-history of the Yellowstone Landscape.

Part I: The Yellowstone landscape is the result of three gigantic volcanic eruptions. Each eruption resulted in the collapse of the volcano into itself, leaving cauldron-like depressions in the land. These land depressions following volcanic eruptions are called caldera. The Yellowstone Caldera, also called the Yellowstone super volcano, is therefore composed of three calderas, which together comprise a large part of Yellowstone National Park. The entire caldera area today measures about 44 miles (72km) long and 34 miles (55km) wide. Most of the lodgings and frequented landmarks in Yellowstone are within this caldera.
The landscape, however, does not appear to be an obvious depression. It is not easy to visualize Yellowstone as a caldera because of the size of it, as well as due to the extensive lava flows that followed the eruptions and filled the depressions. The kind of magma that rose from the collapsed walls of the magma chamber flowed out as a type of lava called rhyolite, which hardened to volcanic soils that now yield forests of pine.
This history of volcanic activity, and the innumerable hydrothermal features in the Yellowstone ecosystem indicate that there is a continued heat-source wielding considerable influence on the landscape, and whose presence is not far from the earth’s surface.  This “hotspot” of molten rock or magma is believed to be just 4 miles below the earth’s surface beneath Yellowstone. While hotspots are common below the surface of the ocean (which give rise to islands, such as, most notably, the Hawai’ian chain of islands), continental hotspots like the one below Yellowstone are very rare. Most volcanoes are on the margins of tectonic plates and are triggered by the dynamics of plate boundaries.  Continental hotspots contribute not just to the volatility of the volcano in question that lies above it, but they also have a tremendous influence on the surrounding landscape. The landscape in Yellowstone is therefore truly unique in all senses of the word. While hot springs and other hydrothermal features are found the world over, notably in Iceland and New Zealand, geothermal features of similar grandeur as those of Yellowstone are perhaps found only in Rotoroua, New Zealand.  The onlooker in Yellowstone cannot help feeling that this kind of beauty is surreal. 

Midway Geyser Basin

The first of the gigantic volcanic eruptions that shaped the Yellowstone landscape took place about 2.1 million years ago. It is believed to have been 2000 times more powerful than the 1980 eruption of Mount St. Helens, and produced 250 cubic miles of rock and debris, and whose “ash buried parts of every state west of the Mississippi river.” Hotspots and Mantle Plumes. The second and smallest eruption occurred 1.3 million years ago. The most recent one erupted 640,000 years ago. Yellowstone Lake, the largest alpine lake in North America occupies a part of the caldera that was created by this explosion.
For the reader who thrills in potential real-life apocalypses, a Google search for ‘yellowstone supervolcano’ will yield abundant leads to doomsday scenarios. Each of the three Yellowstone eruptions occurred roughly 640,000 years apart, and the most recent one was 640,000 years ago….. But no matter how skeptical one is of future eruptions, one cannot ignore the fact that the Yellowstone landscape owes its breathtaking panoramas to past volcanic eruptions of enormous magnitude.
Yellowstone National Park contains about half of the world’s geothermal features. Hydrothermal activity is the result of surface water seeping down and meeting the heat of the earth’s molten rock. The proximity of the magma below Yellowstone has resulted in the impressive numbers and diversity of hydrothermal features in the area. Of Yellowstone’s approximately 10,000 hydrothermal features, more than 250 are active geysers, comprising two-thirds of the world’s geysers. Other features are fumaroles (steam vents), mud pots and hot springs. This diversity, along with the fact that they are being preserved intact are notable features of Yellowstone.
Being in the presence of Yellowstone’s geothermal features is an opportunity to be both amazed and over-whelmed. There is a pervading smell of sulfur. The earth is rarely silent. One detects from all the senses that the ground you are standing on is alive and raging through the bubbling mudpots that spew gases, through the gurgling springs and geysers whose waters burst through with uncanny force and  sometimes regularity, and through the hissing fumaroles with freshly released steam that permeates all the air and everyone present with a sense of enchantment. 

Geothermal Features in Upper Geyser Basin:

Hot spring in Upper Geyser Basin (near Old Faithful)

Bubbling hot spring in foreground with steam from other hydrothermal features in background.

The most well known thermal phenomenon in Yellowstone is the geyser Old Faithful, so named because it erupts with predictable regularity. The range in intervals is 35 minutes to 2 hours. The time to the next eruption is predicted using the duration of the current eruption. The longer an eruption lasts, the longer the time to the next surge.
Old Faithful on a cloudy day.

Iron oxide deposits give the edges of some geysers a gold color which they're named for - Aurum Geysers.


Midway Geyser Basin Features:

Excelsior Geyser

Excelsior Geyser

Edge of Grand Prismatic Spring 

Thermal features in the West Thumb section of Yellowstone Lake:

Fishing Cone Geyser has been a part of the legends of mountain men who spoke of an alpine lake where one could catch a fish and then immediately cook it without even taking it off the line. All one needed to do was to swing the line around and dip it into the boiling Fishing Cone Geyser!
In spring and early summer, Fishing Cone Geyser is submerged due to a rise in the level of the lake following melting snow from the winter.

Colors are created by heat-loving microorganisms (thermophiles). 

Blue Funnel Spring, Central Basin overlooking Yellowstone Lake (West Thumb)

Some short video clips of Yellowstone's geothermal features: