Yellowstone: History of Fire and Ice

Thanks for joining us on this virtual tour of Yellowstone – stay tuned as we blog through the park…Today we are learning more about Yellowstone’s sizzling history of volcanism.

Yellowstone is a land carved by a history of fire and ice, from million of years of volcanism to glaciers, wildfire, erosion and rebirth. Yellowstone is a crossroads of extremes. It is know for it’s diverse and peaceful scenery, which features lush river valleys, chiseled canyons, abundant wildlife and serene backcountry lakes. This is contrasted by basins of steaming boiling hot thermal features including Old Faithful Geyser.

Yellowstone National Park sits on top of a hotspot.

Often we think of hotspots in places like Hawaii where lava erupts with fiery explosiveness – or historically Pompeii in Italy. You imagine a volcano with a cone of lava- Yellowstone is a a bit different – it’s volcanism has formed a ‘living’ volcano of sorts – geology in action.

The Yellowstone Hotspot (a continental hotspot) is one of about 40 known to exist around the world. A hot spot is a plume of superheated material moving up from the core of the Earth through a narrow tube, creating a hotspot beneath the Earth’s crust.

Yellowstone’s hotspot is fueled by a three-layer heat system. In the earth’s upper crust, a huge chamber filled with semi-molten magma lurks about 3-10 miles below Yellowstone. Below this magma chamber, the lower crust hides an even larger magma reservoir 12-31 miles below Yellowstone’s surface. It is filed with thicker magma and below these two chambers, heat rises through the earth’s mantle in a magma plume.

You can learn more about the Yellowstone Hotspot here. The NPS offers a great account of Yellowstone’s geologic history here.

Yellowstone has experienced three major eruptions over the past two million years, with the latest culminating in a supervolcano eruption 631,000 years ago. that led the to the formation of a 30 x 45 mile caldera. The heart of Yellowstone’s thermal activity continues to be by the caldera.

You can still see the rim (the rocky rim is visible most notably by the Madison River Campground or at Washburn Hot Springs overlook, south of Dunraven Pass. Gibbon Falls, Lewis Falls, Lake Butte, and Flat Mountain Arm of Yellowstone Lake are part of the rim.

Quick Fact: The USGS defines a ‘super volcano’ as any eruption flinging more than 240 cubic miles of magma, ash and pumice in one big eruption. Yellowstone continues to be the hotbed of a living ‘super volcano’

Bacterial mats in a thermal basin are home to thermophiles (bacteria) that can survive in extreme temperatures

What makes Yellowstone unique?

  • Yellowstone is the world’s largest supervolcano and it is a national park – which seems a contradiction. Yellowstone gives us the unique ability to see how geology works in action from the unique plumbing systems that fuel geysers and thermal activity.
  • Volcanism has defined every landscape in Yellowstone from petrified stone forests and craggy canyons to features like Obsidian Cliff. This combined with glaciation, wildfire, erosion has sculpted a diverse terrain of vast valleys to jagged peaks, lakes and canyons. Yellowstone is science and life in motion!
  • Yellowstone is home the world’s largest concentration of thermal features, including 10,000 geysers, fumaroles, hot springs, mud pots. Over 55% of the world’s geysers erupt in the park boundaries including the world most famous geyser Old Faithful, and the world’s most powerful geyser Steamboat.

Thermal Features in Yellowstone

Many of Yellowstone’s thermal features are concentrated in areas known as ‘Geyser Basins’ – Geyser Basins are tied by common subterrain plumbing. Visitors can explore most of the basins via boardwalks (Upper and Lower Geyser Bains; Norris, Mammoth, West Thumb, Mud Volcano…). There are several backcountry basins like Shoshone and Heart Lake that require hike in/out to reach. I’ll be blogging through these areas on our virtual tour in the coming weeks.

  • Each Geyser/Thermal Basin is unique and worth visiting.

TREAD carefully. Thermal features are HOT – some over 300 degrees and many have been seriously injured and died from going ‘off trail’/’off boardwalk’ Don’t play with fire you will get burned.

Yellowstone includes several times of thermal features including:

  • Geysers blow super-hot water into the air. Some erupt non-stop, while others blow on schedule, intermittently or after many years of dormancy. Eruptions result from big clogs of boiling water. After surface water percolates down to a hot spot, it then boils toward the earth’s surface…pressure builds as the water erupts at the earth’s surface when gas bubbles reach the air.
    • Cone geysers like Old Faithful blast water upward in a narrow stream
    • Fountain geysers like the Great Fountain Geyser spray water in multiple directions
  • Hot springs are the most common hydrothermal features in Yellowstone. Beginning as precipitation, the water of a hot spring seeps through the bedrock underlying Yellowstone and becomes superheated at depth. An open plumbing system allows the hot water to rise back to the surface unimpeded. Convection currents constantly circulate the water, preventing it from getting hot enough to trigger an eruption. From NPS
Water temperatures within some springs exceed the boiling point. The intense blue color of some springs results when sunlight passes into their deep, clear waters. Blue, a color visible in light, is scattered the most and the color we see.NPS
  • Fumaroles – are some of my favorite features because they feel so otherworldly. Fumaroles are holes or vents in the ground, but instead of filling with hot water, they convert the small amount of water into super hot steam. Examples: Black Growler in Norris Geyser Basin
  • Mud Pots form in depressions when hot water saturates clay-like sediments. Below the mud pot, as steam pushes upward into the saturated sediments, gaseous bubbles surface to pop and gurgle. Mud pots often have hydrogen sulfide gases that produce a rotten egg smell. Fountain Paint Pots is a popular roadside spot to check out paint pots
  • NPS has a great guide to Yellowstone’s unique thermal features to learn more click here.

Hopefully this introduction to Yellowstone’s geology has piqued your interest to learn more.

When you arrive at Yellowstone – I recommend taking time to visit the Old Faithful and Canyon Village visitor centers. These two state of the art educational museums dive deep into how volcanism at YNP works. Canyon has a scaled model of eruptions and interactive exhibits that help everyone graduate from junior ranger to ‘honorary geologist’

Want to read more about Yellowstone’s geology?

In addition the NPS links I included I recommend the following books:

Roadside Geology of Yellowstone

Outside Magazine’s Yellowstone Geyser Guide

references: NPS, Official Souvenir Book to Yellowstone; Moon Guide

Next time we’ll start our journey at Mammoth Hot Springs and dig into Yellowstone’s human history…

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