Lassen Volcanic National Park

Listen for a moment. Somewhere nearby, the ground is hissing. There is a faint smell in the air too, sharp and eggy, carried on the mountain wind. Under your boots the earth may feel ordinary, but it is not. This is Lassen Volcanic National Park, in the far north of California, and the land around you is still very much awake.

The mountain at the centre of it all is Lassen Peak. It rises to about 3,187 metres, a grey and rust-coloured dome that holds snow well into summer. It is the southernmost volcano in the Cascade Range, the long chain of peaks that runs north through Oregon and Washington. Mount Shasta, Mount Hood and Mount Rainier are its distant relatives. Lassen simply happens to sit at the very end of the line.

Here is the first surprise. Lassen Peak is not a classic cone-shaped volcano. It is a plug dome — a huge mound of thick, sticky lava that squeezed up through a vent and piled on itself, like toothpaste that is too stiff to flow. Geologists consider it one of the largest plug domes on Earth. When you look at its rough, broken summit, you are looking at lava that hardened almost where it emerged.

Now the second surprise. This one park holds examples of all four main types of volcano. Lassen Peak is the plug dome. Prospect Peak, to the northeast, is a shield volcano — broad and gentle, built from runny lava. Cinder Cone, in the park's remote corner, is a steep pile of loose volcanic rock. And Brokeoff Mountain is the eroded remnant of a much older composite volcano that geologists call Mount Tehama. Few places on Earth gather all four so closely together.

Mount Tehama deserves a moment. Long before Lassen Peak formed, this giant stood in the southwest of today's park. Over a very long time, heat and acidic steam weakened its core, and rain, snow and glaciers carried much of it away. What remains is a ring of ridges, with Brokeoff Mountain as its highest surviving edge. The hot springs and steam vents you find today sit roughly where the heart of that old mountain once was.

Then came the twentieth century. In 1914, Lassen Peak began to stir, with small steam explosions near the summit. They continued for months. In May 1915, the mountain erupted in earnest. Lava rose into the crater. Hot material melted the deep snowpack, and floods of mud and rock rushed down the northeast slopes. Days later, a powerful blast sent a column of ash high into the sky, visible from towns far across the valley.

One man made sure the world could see it. A local photographer named Benjamin Franklin Loomis captured the eruptions and their aftermath in a remarkable series of images. His photographs remain among the best early records of a volcanic eruption in the United States. Today a museum at Manzanita Lake carries his name, and his pictures help visitors imagine what this quiet landscape looked like in fury.

The eruptions also changed the mountain's legal fate. In 1916, while the volcano was still restless, Congress created Lassen Volcanic National Park. For decades afterwards, Lassen held a quiet distinction. Until Mount Saint Helens erupted in 1980, it was the most recent major eruption in the lower forty-eight states. If you drive the main park road, you can still pass through the Devastated Area, where the 1915 mudflows tore through the forest. Look closely and you will see young trees growing back among large volcanic boulders.

The name itself comes from Peter Lassen, a Danish-born pioneer who guided settlers through this region in the mid-nineteenth century. But people lived here long before him. The Atsugewi, Yana, Yahi and Maidu peoples knew these mountains, meadows and springs for countless generations. They hunted, gathered and travelled through this land, and the area around the park remains meaningful to their descendants today.

Now, back to that smell. The park's best-known hydrothermal area is called Bumpass Hell. It takes its name from Kendall Bumpass, a nineteenth-century local man who, according to the commonly told account, broke through the thin crust here and badly burned his leg. A boardwalk now crosses the basin. Around it you will find boiling pools, bubbling mud pots and steam vents called fumaroles, where volcanic gas escapes from deep underground.

The colours at Bumpass Hell are worth the walk on their own. Pale grey clay, chalky white crust, streaks of yellow sulphur and pools of milky blue water sit side by side. The heat and acidic gases slowly break the rock down into this soft, bleached ground. It looks solid. Often it is not. That is exactly why the boardwalks exist, and why staying on them is not a suggestion.

The park is not only steam and stone. There are clear mountain lakes, like Manzanita Lake, where on a calm morning Lassen Peak can appear upside down on the water. There are green meadows, wildflowers in summer and dense conifer forests. In winter, deep snow closes much of the main road, and the park becomes a place of silence and skis. At night, far from city lights, the sky here fills with stars.

So take a slow breath before you move on. Feel the cool mountain air, and notice the faint warmth or sulphur drifting from the ground. Look up at the broken summit of the peak, and then down at the rock beneath your feet. All of it was shaped by fire, and the fire has not left. As you walk away, listen once more for that low hiss — the sound of a mountain that is resting, but still breathing.