Yellowstone’s Grand Prismatic Spring

Growing up in Delaware, I had never seen anything like it. We crossed a bridge over a burbling stream, clambered up a copper-toned hill and there it was: Yellowstone’s Grand Prismatic Spring. Alone on a wooden walkway, I inhaled the warm, earth-scented vapors that glided across the turquoise water. Otherworldly? Yes. But, surprisingly even here, in this stunning but inhospitable place, there was life and things were growing.

KALEIDOSCOPE EYES – PANIC! AT YELLOWSTONE

First described in 1871 by the Hayden Expedition, the Grand Prismatic Spring is the third largest hot spring in the United States. Veiled in steam, it bubbles like a bathtub, offering a glimpse now and then into its churning caldron. The deep blue pool is impressive, but more surprising still are the tentacles of golden yellow, burnt orange and metallic green that fan outwards from the roiling waters. Seemingly not of this earth, they carve kaleidoscopic paths across the scorched soil.

Grand Prismatic Spring from new overlook trail

Upon seeing the spring for the first time, Ferdinand Hayden (the leader of the Expedition) wrote:

Nothing ever conceived by human art could equal the peculiar vividness and delicacy of color of these remarkable prismatic springs.

It’s enough to make your head spin.

ABOUT YELLOWSTONE’S HOT SPRINGS

Of the many different kinds of hot springs at Yellowstone National Park, Old Faithful is one and Grand Prismatic Spring is another. Both result from groundwater that has been heated by molten magma and risen to the surface. In the case of Old Faithful, however, the hot water encounters blockages on its way up. This produces the famous geyser’s explosive eruption of steam.

Old Faithful

The Grand Prismatic Spring, however, encounters no blockages, instead rising to the surface through cracks in the earth’s crust. This allows for a continual flow of water that rises, cools and falls back, only to rise again. As a result, the vapors stay close to the earth, roiling slowly around the molten rock.

A glimpse into the turquoise depths of the spring

GRAND PRISMATIC SPRING IS YELLOWSTONE’S LARGEST

Pouring almost 500 gallons of scalding water per minute into nearby Firehole River, Grand Prismatic Spring is the largest and most brilliant-colored of Yellowstone’s many hot springs. The high temperature of the spring (estimated at around 160 degrees F) is responsible for the steam that hovers 24/7 above the crater.

Due to this cycle of heating, cooling and re-heating, the spring has developed rings of varying temperatures. The hottest water, which is located in the center, is too extreme for living things. However, as the water spreads outwards, it gradually cools, allowing for conditions more amenable to life to develop.

Bands of color at Grand Prismatic Spring

Happily, the viewing boardwalk provides safe passage for humans atop the smoldering landscape. And there is good cause for concern. Along the way, signs warn against the dangers of straying, citing stories of how people have been scalded, children killed and family pets sucked into the vortex. Indeed, even standing too close to the spring can cause intense burns.

The viewing boardwalk at Grand Prismatic Spring

So how can life exist in such harsh conditions? The answer lies in the prismatic colors. Each of these stunning hues harbors billions of colorful microorganisms that live in the spring’s runoff channels. These ‘extremophiles’ (so named for their ability to live in conditions that were once thought too hot to host life) are not only surviving, but thriving, happily assembled in thick, microbial mats.

MINIATURE MICROBIAL FORESTS

Microbial mats may not sound all that interesting until you consider that each of these burgeoning communities is in fact a miniature ecosystem functioning much like a forest. There’s a ‘canopy’ of microbes performing photosynthesis. And, there’s an ‘understory’ of organisms playing the crucial role of decomposition and recycling of nutrients back to the canopy.

The rainbow of colors that the mats produce depends on the temperature of the water. In the summer, the mats tend towards brown, orange or red and in the winter they gravitate towards dark green.

Microbial mats radiating outwards from Grand Prismatic Spring

WHAT ACCOUNTS FOR THE YELLOW/ORANGE COLOR

Cynobacteria, marine bacteria that obtain their energy through photosynthesis, are one common organism found growing by the Grand Prismatic Spring. In the world’s oceans, cynobacteria occupy an important position at the bottom of the food web. At Yellowstone, however, they have had to make some ecological adjustments. These are evidenced in the distinctive yellow/orange color of the spring’s outer ring.

Yellowstone’s extreme temperatures, high altitude sun and lack of shade can quickly overwhelm the photosynthetic process. But, a certain strain of cynobacteria has learned to survive the heat by adjusting its ratio of chlorophyll to carotenoids. During the hottest months, rather than staying green, they employ carotenoids as shields. This results in their summertime yellow/orange color.

Close-up of some of the microbial communities

As you move further from the spring, more and more lifeforms can be found. Cynobacteria are joined by other strains whose combined colors read as orange. Finally, as the temperature cools, the communities of bacteria at the furthest points produce the darkest color, a molten shade of coppery-brown.

View of spring from bridge

Hard to believe these mini orange and brown ‘forests’ are existing right under our noses. Life is pretty amazing.