
Mendenhall Glacier Ice Caves, Alaska
Blue ice caves appear and disappear inside Mendenhall Glacier as it slowly melts back toward the mountains. Here’s how these short-lived caves work and why they keep changing.

Why These Caves Look So Blue
The thick ice soaks up all colors except blue, which passes through the frozen glacier. And unlike regular ice, glacier ice has no bubbles, letting light travel deeper and spreading those sapphire shades.

How These Ice Tunnels Form
Water always finds the easiest path forward, and summer meltwater creates these caves by flowing between the glacier and the ground.
This slightly warmer water melts the ice around it, carving tunnels that grow into caves. Glacier experts call the entrances “moulins.” Some are tiny holes while others form huge archways.

A Glacier in Retreat
Mendenhall has pulled back 2.5 miles since the mid-1700s. Before that, it only retreated half a mile over 250 years. It’s shrinking faster than it ever has.
About 1.75 miles of retreat happened just since 1929, when Mendenhall Lake first formed from glacier meltwater. Today, the glacier shrinks 100-150 feet every year. Soon, scientists say, it won’t even touch the lake anymore.

Here Today, Gone Tomorrow
These amazing ice caves don’t last long. Some exist for days, others for months, but all eventually disappear.
Late summer brings stronger water flows that speed up melting. Cave entrances collapse when supporting ice weakens, and the old caves vanish while new ones form elsewhere as water cuts fresh paths through the glacier.

The Sounds of Ice on the Move
Ice caves work like natural amphitheaters. Inside, you hear creaks, groans, and sharp cracks as the massive glacier shifts above you.
Water flowing through moulins echoes from gentle trickles to roaring torrents. Though too slow to see, the glacier’s constant movement creates unique sounds as ice compresses and breaks. Streams underneath add their own chorus of rushing water.

The Real Dangers Inside
These caves can kill you. Ceilings collapse without warning as the glacier shifts. Near entrances, refrigerator-sized ice chunks litter the ground from recent collapses.
Heavy rain or fast melting can also flood caves in minutes. The most dangerous caves form from overhanging ice which lack the stability of water-carved tunnels and can come crashing down at any moment.

Getting to the Caves
Reaching these hidden chambers takes work. Most summer visitors kayak across Mendenhall Lake then hike rocky terrain to the glacier’s edge.
The West Glacier Trail gets you most of the way, but the final stretch has no marked path. In winter, when the lake freezes, people walk across the ice to reach caves on the glacier’s west side.
Each year, access gets harder as the glacier retreats farther up the valley.

Visiting Mendenhall Glacier Ice Caves
Located at 6000 Glacier Spur Road, Juneau, Alaska, the Mendenhall Glacier Visitor Center charges $5 for ages 16+ (May-September). Summer hours are 10am-5pm Sunday-Friday, closed Saturdays.
Currently, accessible ice caves no longer exist due to glacial recession, and the famous caves collapsed by 2023.
However, you can book guided adventure tours via canoe and glacier trekking.
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