Geologic and Yellowstone

The work of heat  and time at Yellowstone

Idaho's Snake River Plain stretching across southern Idaho is witness to earth's incessant movement. While the North American Continental Plate has drifted steadily southwest over millions of years, a hot spot in the molten earth's core has remained stationary and has erupted about a dozen times in the past 17 million years, releasing massive amounts of rhyolite magma and ash. The resulting craters, 10-40 miles wide, have laid down the path of today's Snake River. In between the super-eruptions fluid basaltic lava has continued to flow from more then 8,000 shield volcanoes and numerous lava cones in southeastern Idaho. The basalt, 3,000-6,000 feet deep, is now carpeted above with the sage prairies and buttes of Eastern Idaho, while the Snake River waters wondrously fertile land.

Yellowstone River

The hot spot, a deep thermal mantle plume of molten rock, is now under Yellowstone National Park in neighboring Wyoming, home to 10,000 geysers, hot springs, mud pots and steam vents--more than anywhere else on earth. Another eruption of the Yellowstone Super Volcano, which will happen sooner or later, would plunge the Earth into darkness.

Yellowstone National Park was created by an act of Congress and signed into law by President Ulysses S. Grant in 1872. It has been designated a US Biosphere Reserve, a World Heritage Site, and is one of the largest national parks in the lower 48 states. We entered the great park from the west, along sparkling waters and lower grassy marshland, darkened in places with red-tipped Indian grasses. On a little island three male elks chewed, their monumental antlers turning this way and that. It is impossible to describe how pristine the sagebrush and wild lavender are, an environment enveloped in sharp and sweet fragrances.

Grand Canyon of Yellowstone

We headed for the Grand Canyon of Yellowstone. It is a more aesthetic and compact experience than its eponymous neighbor, with brilliantly colored walls of old rhyolite lava flows and foaming green waters, the Yellowstone River snaking in and out of sight between layers of geologic time and thermal coloration. It is more than 1,000 feet deep in most places, up to 4,000 feet wide, and 20 miles long. Every lookout on the drive is worth the hot and laborious parking. Large birds hidden high in pines called and rustled loudly through the treetops. A raven made herself comfortable on an SUV, scolding.

The Grand Canyon of Yellowstone was born thousands of years ago and is still being changed by the heat and gases of the Yellowstone Volcano. An icecap that melted 14,000 years ago began the river's flow, sculpting of the old rhyolite lava, aided by wind, rain and gravity. Heat and gases continue to soften the canyon walls and catalyze their constant transformation. The river's waterfalls thunder into mist, covering the walls with cool hanging gardens.

Elk on the village green

Our second day at Yellowstone we entered from the arid northern deserts of Yellowstone to visit the thermal world. Mammoth Hot Springs heats the ground and has attracted elks for a century. Its perfectly molded terraces in seashell and molusk shapes are colored by bacteria that catalyze bright minerals like iron and sulfur dioxide. Shoshone and Bannock people used to collect minerals here for their white paint. The brighter ochre colors come from thermophiles, heat-loving organisms, whose color indicates the temperature of their environment. Atop Mammoth Springs grow twisted pines, bleached barkless trunks. a forest of gnarled spirits. Some of the limber pines are said to be 500 years old.

Mammoth Hot Springs

The Obsidian Cliff, further along the road, bears no marker--visitors are discouraged from this national historic monument, because they have carried off so much obsidian as to dull the glass wall. Obsidian collected here was traded across North America by Native Americans.

Porcelain Basin

All day we stood over the steam vents of smoldering earth, sapphire and turquoise pools whose clarity and luminosity suggested coolness, not heat, painted around with ochre and umbre and mustard yellows, belching heated gurgling bubbles or steam or shooting geysers, sometimes surprising us with short intense fountains.

Sapphire Pool

At the Porcelain Basin at Norris, the park's hottest exposed basins, Jacques had to test the toxic shallow water, seething and bubbling over a beautiful palette of blues.

At Midway Geyser basin, pools rumble and bubble, all witnesses of intense dynamism, all emerging from the shifting, restive magma that has the power --someday, in a thousand or ten thousand years --to obliterate our hubris. The beautiful paradise burns into whiteness, the animal droppings are dry pies around the hot cracked environs.

The ochre and red colors come from miniature forests of microorganisms. For thousands of years, microbes have grown in the runoff channels extending from nearby Grand Prismatic Spring, then were buried alive under a crust of silica minerals. The resulting mats, layered upon each other, contain living and nonliving components. Surface microorganisms perform photosynthesis, while deeper inside, as if on a forest floor, organisms feed off the upper layers, an entire ecosystem in a few centimeters.

The Grand Prismatic Hot Spring has a layer of turquoise steam rising from the surface. It is the park's largest spring, approximately 200 ft across, at 160 degrees F. Deep beneath, magma from the active super volcano heats water that rises to the surface through fissures in the rocks and pours almost 500 gallons of hot water each minute into the Firehole River.

Grand Prismatic

Excelsior Geyser Crater erupted during the 1880's in bursts 50-300 ft high, till it apparently blew out in 1890. On Sept 14, 1985, Excelsior roared back to life with 47 hours of major eruptions.

Though its eruptions have been erratic, the geyser's outflow is nearly constant, pumping more than 4000 gallons of boiling water per minute over the crater rim into the Firehole River.

Old Faithful at rest

We finished our tour at Old Faithful, where crowds gathered to wait for the eruption. A guide had begun to explain the mechanism which makes Old Faithful periodic and relatively predictable--a narrowing in the vertical canal lets heat build up till its force is tremendous, expelling 3,700-8,400 gallons of boiling water to a height of 106-184 feet. Just as the guide reached the point of eruption in her story--there she blew!

Old Faithful in action

In the distant past, volcanism covered the earth.  Now it is the environment of Yellowstone that teaches us about the ancestral life of earth's vast biodiversity.