Monday, August 01, 2005
Is Yellowstone a super volcano?
This is Yellowstone, wild and peaceful, as most people know it.
Few realize that America's flagship national park is also a place of unimaginable violence. Catastrophic destruction on a scale beyond all human experience has ravaged the region many times.
"Yellowstone is a living volcano," says Robert B. Smith, a Utah seismologist who has spent much of his career studying one of the most dramatic geologic stories ever told.
It's no ordinary volcano. Yellowstone is one of Earth's few supervolcanoes. The last eruption, 10,000 times greater than the 1980 eruption of Mount Saint Helens, changed the face of North America and wreaked havoc around the globe.
Smith and his colleagues -- who have unearthed the astonishing narrative of destruction and re-creation -- tell us that while there are no signs of imminent doom, about 100 catastrophic eruptions have occurred in the past 17 million years. The latest three happened at 2 million, 1.2 million and 630,000 years ago. Almost certainly, it will happen again.
That's no reason to cancel vacation plans. On the contrary, it's another good reason to visit the park. The wildlife, pristine scenery, geysers and hot springs are all as delightful as ever.
But they are only the surface of a deeper truth. If you look at Yellowstone as the still-smoldering scene of catastrophe, you have a whole new perspective, and some grimly fascinating stories with which to impress the kids. Big boom, indeed.
Yellowstone National Park is primarily in the northwest corner of Wyoming, extending into Montana and Idaho. Jackson, Wyo., is the nearest air gateway. These resources can enlighten:
• Quake updates: The Yellowstone Volcano Observatory Web site has maps, photos and monthly updates about seismic activity. The observatory is a partnership of Yellowstone National Park, the U.S. Geological Survey and the University of Utah.
• Geological background: Windows Into the Earth ($40; Oxford University Press), written by Robert B. Smith and released in 2000, provides a thorough explanation of Yellowstone geology and a detailed driving tour.
• Planning a trip: basic Yellowstone information supplied by the National Park Service.
• Lodging: Xanterra Parks & Resorts is the primary in-park concessioner at Yellowstone. No booking fee is charged.
-- CHRONICLE NEWS SERVICES
It's not obvious that Yellowstone is a volcano. It does not have the classic shape of Japan's Mount Fuji or Italy's Vesuvius, built by relatively small eruptions.
When Yellowstone erupts, it blows itself to bits. It hurls whole mountain ranges into the atmosphere and belches out so much matter that it collapses into its own emptied space. The result is not a shining cone, but a caldera, a great smoking pit. Yellowstone's last eruption left a caldera measuring 30 by 50 miles.
The cause of it all is a hotspot -- a plume of molten and semimolten rock that rises upward from deep beneath the Earth's crust. Worldwide, there are about 30 hotspots. Almost all of them are beneath oceans. They remain stationary as the crust drifts over them. When they break through, the lava they pour out creates island chains like the Galapagos and Hawaiian archipelagos.
The Yellowstone hotspot is unique. Located beneath the continent, it erupts less frequently than its ocean-floor counterparts but with greater force. When it first erupted nearly 17 million years ago, it was beneath Oregon. As the continent drifted west, the sequence of eruptions left a path of destruction, a trail of calderas across southern Idaho into Wyoming.
The most recent caldera has been obscured by lava flows from smaller, subsequent eruptions. Glaciers smoothed the edges and carved valleys. Yellowstone Lake fills a large portion of it. Yet much remains visible if you know what to look for.
Touring the sitesA tour of the cataclysm can be made by driving the park's 86-mile Lower Loop Road, which connects Old Faithful Geyser, Yellowstone Lake, the Grand Canyon of Yellowstone and other important sites. The loop is entirely within the caldera. It can be driven in a day, although locals claim a lifetime is not enough.
You could start anywhere on the loop, but the best place is on Mount Washburn, north of Canyon Village at Heart of the Caldera Overlook. From here, the view sweeps down to Yellowstone's version of the Grand Canyon and across to the rolling, forested expanse of the Mirror Plateau. A large part of the plateau is a resurgent dome, a bulge caused by pressure from beneath -- a sure sign that things are still happening down under.
A person standing here 630,000 years ago would have seen the ground drop away at his feet as the caldera collapsed -- except he'd have been vaporized first, by the upward blast of the explosion, which sent curtains of rock flying faster than the speed of sound.
Half of Mount Washburn disappeared in that or one of the earlier blasts, along with a 40-mile chain of peaks stretching south to the Red Mountains. Those summits can be seen in the distance. They mark the far side of the caldera.
Mud VolcanoDown the road 10 miles is a volcanic kid-pleaser: the roiling, stinky cauldrons of Mud Volcano. One of the pools is more acidic than a car's battery. A boardwalk leads up the hill to lakes of steaming mud that came to life not long ago in the midst of living forest.
FUN: With comical eruptions of boiling clay, mudpots mimic the volcanic action that created them.Some of the trees, bleached and gaunt, stand hip-deep in hot bubbling mud. The turbulence mimics the eruption of lava. The air reeks of hydrogen sulfide, which makes for family jokes all the way to the next stop, Le Hardy Rapids, several miles south.
The rapids are caused by a fault line that crosses the Yellowstone River. Between 1928 and 1985, the ground on the upstream side rose more than three feet. It fell for a few years after that, then resumed rising. Does that signal an imminent eruption?
Not likely, Smith says. It's just the natural ebb and flow of pressure from the hotspot. Yellowstone breathes. No wonder they say it's alive.
If you turn east at Fishing Bridge, you can imagine driving on the crater floor, still steaming thanks to frequent hot springs. Pelicans, swans and grazing moose offer distractions, but don't pass up the side trip to Lake Butte Overlook, another point on the caldera rim and one of the park's great views.
That big open space -- the glittering lake, the forested plateau, the 40-mile gap between mountains -- once had lots more in it before it was all blown to Kansas and points eastward. If you could pile all the ejected ash and rock from the last eruption in one place, it would cover South Carolina 100 feet deep.
From here, return to Fishing Bridge and continue around the north shore to West Thumb, where a charming little geyser basin adds its hot water to the cold lake. It's worth a stop, but the big show lies ahead at Old Faithful.
To get there, the road climbs high over hills of lava. Crossing the Continental Divide twice, it then drops into one of the strangest places on Earth -- the Firehole Valley, location of the most geysers, steam and boiling water this side of the planet Venus.
Here more than anywhere else in the park, a visitor gets a sense of the magma engine pounding away just five miles down. It's best seen in the cool of morning when shaggy bison drift through dense mist and the whoosh of geyser water mingles with the metallic croaking of unseen ravens.
HEAT: Colors radiating from the center of Grand Prismatic Hot Spring are ribbons of multihued heat-loving algae.Besides powering the geysers and bulging out like so much magmatic cellulite, the hotspot also keeps the place rocking. Earthquakes occur frequently, sometimes hundreds in a day. Most are very small, detectible only by instruments. One very big one -- magnitude 7.5 -- occurred in 1959. It triggered a landslide at Hebgen Lake west of the park. A campground was buried, and 28 people died.
Beyond the Lower Geyser Basin, the road drops to Madison Junction. Straight ahead, on the north side of the Madison River, that wall of broken cliffs is another part of the caldera rim. Those rocks witnessed the cataclysm. They stood, unmoving, on the edge of the great collapse 630,000 years ago.
From here, the loop road climbs gradually beside the waterfalls and hissing cascades of the Gibbon River. The kids might want to dangle toes in the clear water, or pause to watch bison and elk that frequent the justly named Elk Park. Not far ahead lies Norris Geyser Basin, the hottest ground in the park. In places, the surface rocks are at boiling temperature.
Something's always happening at Norris. In 1989 a geyser blew itself to smithereens. Startled visitors dodged flying rocks. Recently, changes in ground temperature forced closure and rerouting of a main trail. Last summer, a long-forgotten geyser came suddenly to life. Rangers referred to history books to find its name.
The late renowned park geologist, Roderick Hutchinson, predicted that when lava again erupts in Yellowstone, its first appearance will be at Norris. Some might welcome that, if it were a small eruption, perhaps a little Vesuvius-size eruption. That would allow us to stand some distance away -- perhaps on Mount Washburn, 10 miles east -- and exclaim on the power and wonder of the Earth.
Then everyone would understand, from a safe vantage point, that Yellowstone is truly a living volcano.