What is the largest active volcano in the United States?

Forget Hawaii, This Alaskan Giant is the REAL Volcano Champ!

When you think of active volcanoes in the US, what comes to mind? Maybe Mount St. Helens’ ghostly silhouette, or the fiery rivers of lava snaking through Hawaii’s volcanic landscapes. But hold on – there’s a contender for the title of “largest active volcano” that often gets overlooked: the mighty Mount Wrangell in Alaska.

Tucked away inside Wrangell-St. Elias National Park and Preserve, Mount Wrangell is a true behemoth. It’s a shield volcano, meaning it’s built from layer upon layer of slowly oozing lava, giving it a broad, gentle shape. Picture a giant, flattened dome rising a staggering 14,163 feet (that’s 4,317 meters!) above the Copper River – a truly dominant landmark in the vast Alaskan wilderness. And get this: its volume is estimated to be over 220 cubic miles (920 cubic kilometers)! To put that in perspective, it’s more than double the size of Mount Shasta, that classic stratovolcano we all know from the Cascade Range.

A Sleeping Giant… Or Just Playing Coy?

Okay, so “active” might be a bit of a stretch compared to Kilauea’s constant fireworks. Mount Wrangell is more like a sleeping giant, occasionally stirring in its slumber. There are whispers of past eruptions in 1784 and 1884–85, but some say those are just tall tales. The last time it definitely burped was in 1884, with a minor phreatic eruption (basically, a steam explosion). These days, the biggest clue that it’s still alive is the presence of fumaroles – vents that puff out steam and volcanic gases – near its summit.

Speaking of the summit, it’s a sight to behold: a massive caldera, like a giant bowl carved out of the mountaintop, measuring roughly 2.5 by 3.7 miles (4 by 6 kilometers). And what’s inside that bowl? Ice. Lots and lots of ice. Three small craters nestle within this icy expanse, often venting those telltale plumes of steam that you can spot from miles away on a clear day. Experts believe this whole caldera formed not from a massive explosion, but from the ground slowly sinking in on itself – a process called subsidence.

Keeping an Eye on the Beast

Just because it’s quiet doesn’t mean we ignore it. Scientists are constantly monitoring Mount Wrangell, and for good reason. Back in the mid-20th century, from the 50s to the 80s, they noticed a surge in geothermal activity. The ice around those summit craters started melting, creating some pretty cool ice caves and little lakes. Things have cooled down a bit since then, but the potential for future eruptions is always there. That’s why the Alaska Volcano Observatory (AVO) keeps a watchful eye on Wrangell, analyzing seismic data and jumping on any reports of unusual activity.

Fire and Ice: A Truly Alaskan Story

What makes Mount Wrangell so fascinating is the way fire and ice collide in this extreme environment. Almost the entire mountain is draped in a year-round icefield. And Nabesna Glacier, Wrangell’s largest, feeds the Nabesna River.

The Wrangell Mountains, with Mount Wrangell at their heart, are the volcanic engine of Wrangell-St. Elias National Park. This whole region is a powerful reminder of the forces that have sculpted Alaska over eons.

While Hawaii’s Mauna Loa might be the undisputed heavyweight champion of active volcanoes worldwide in terms of sheer size and mass, when we’re talking about the United States, Mount Wrangell takes the crown. Its massive scale and ongoing, if subtle, activity make it a truly remarkable geological wonder. It’s a reminder that even in the quietest corners of the world, the Earth is still very much alive.