How does an ice cave in a glacier differ from an underground cave with permanent ice?

While the term "ice cave" is often used interchangeably, it refers to two distinct geological phenomena that are wholly unrelated.1

Glacier Caves

A glacier cave is a tunnel formed entirely within a glacier or snowfield. These are created by meltwater streams that drain from the surface through crevasses, carving tubular conduits at the base of the ice. Because they are composed of glacial ice, these caves often feature translucent, scalloped walls that transmit blue light. They are typically temporary, as they are often filled with water or subject to melting, and are generally accessible only when surface temperatures are freezing.123

Underground Caves with Permanent Ice

In contrast, an underground cave with permanent ice is a standard rock cavern—such as those found in limestone or lava—that contains perennial ice deposits. These form when frigid winter air becomes trapped in downward-leading caverns or when moisture freezes within cold air currents. Unlike glacier caves, these structures are defined by their ability to remain protected from summer heat, allowing ice formations like icicles, frozen lakes, and ice draperies to persist throughout the year.12