On the drive from West Thumb to Old Faithful, the road crosses the Continental Divide twice, the second crossing being Craig Pass at elevation 8,262 feet. Straddling Craig Pass is Isa Lake (more like a large pond in my opinion), one of the only natural water bodies in the world that drains into two oceans; in Lake Isa’s case, the Pacific and the Atlantic.
The Old Faithful viewing area has changed dramatically since we were here last in 1993, but the geyser itself remains the same, faithful as ever, erupting for 2 to 5 minutes every 90 minutes or so (here’s the eruption schedule). Each eruption spews steam and boiling-hot water – an average of 28,000 gallons of it – as high as 184 feet in the air!
There are several hydrothermal features in Yellowstone: geysers; fumaroles; hot springs; mudpots; and, travertine terraces. The first three are found here around Old Faithful in the Upper Geyser Basin.
From the Old Faithful viewing area, there’s a boardwalk trail that heads north, crossing the Firehole River. The boardwalk makes a loop around Geyser Hill, following the river downstream about 1.4 miles to a hot spring called Morning Glory Pool. The return from there is on a graded bike path on the south side of the river, back upstream to Old Faithful.
Before setting out on the boardwalk, we first wandered along the southern shore of the Firehole River to Chinese Springs where we could see the steam vents and the run-off from the various geysers and pools that feed the river.
Our first stop on the boardwalk trail was to look back at Old Faithful (top left in photo, below) and at the historic Old Faithful Inn, built in 1903-04 and designated an historic landmark in 1973. In the foreground, below, is the Anemone Geyser, one of the more frequently erupting geysers in this basin, throwing water about six feet into the air every 10 minutes or so.
Further along the trail, we stopped to admire the hot spring known as Heart Spring. Hot springs are closely related to geysers, the difference being the extent of restriction in the underground channels and chambers that feed them. Geysers have narrow underground plumbing that traps water percolating down from the surface until it becomes superheated, expands, turns to steam and rises, forcing the water above high into the air. Hot springs, on the other hand, do not have such constrictions so there is no build-up of pressure in the system. Instead, the water is able to circulate, slowly rising to the surface where some of the heat escapes either into the atmosphere through evaporation or as runoff onto the surface.
Many of the hot springs and geysers are circular, like Churn Geyser, below.
From Churn Geyser, we crossed back over Firehole River to see Crested Pool and Castle Geyser, stopping briefly to look upstream at the fumaroles lining the shore. Fumaroles, or steam vents, are the hottest features in Yellowstone. Their underground systems hold very little water, so any rain or melted snow that does make its way down from the surface is vaporized when it reaches the hot rock mass and instantly rises as steam.
Here’s the Crested Pool which is almost constantly boiling to a depth of 6 feet or more. The extreme heat in this pool keeps bacteria from growing, resulting in crystal clear blue water.
Just beyond Crested Pool is Castle Geyser, built up over thousands of years, which historically erupted every 14 hours or so, but now seems less predictable. We contented ourselves with watching it simmer, then moved on back across the river to continue our walk.
Back on the north side of the river, we came upon another geyser viewing area, this one a twofer: Grand Geyser (a fountain geyser, right) and the smaller Vent Geyser (a cone geyser, left), which seemed to be constantly erupting as we passed by.
One of the prettiest hot springs in the basin is Chromatic Pool, below. The variety of colors in this pool is the result of varying temperatures that create multiple environments for different types of living organisms (mosses at 122°, protozoa at 133°, algae at 140°, fungi at 144° and cyanobacteria at 163°F), each of which reflects a different color.
We crossed over the Firehole River again and continued just a little further before turning back where Link Geyser flows into the river. I couldn’t resist sticking my hand into the runoff to test the temperature. I’m guessing the water is about 150°F where I touched it about 50 feet from the geyser; I was only able to keep my hand submerged for about 5 seconds before it started to hurt.
On the walk back to Old Faithful on the bike path, we could see the entire Upper Geyser Basin that we had just walked through, home to a majority of the world’s active geysers.
We had been walking for about 90 minutes when we arrived back at Old Faithful, just in time to catch another eruption, this time from the other side where the wind carried the plume away from us, making it much easier to photograph.
An enjoyable day.