active ice wedge

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July 23, 2026

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An active ice wedge is a large, wedge-shaped mass of ice within permafrost that is actively growing. These ice wedges form in polygonal networks and require very cold climates, with mean annual air temperatures of -6 to -8 °C (21 to 18 °F) or colder, for contraction cracks to form and fill with meltwater that freezes. This process repeats annually, adding increments of ice and causing the wedge to grow. Active ice wedges are typically found in continuous permafrost zones. Inactive ice wedges are no longer growing, and ice-wedge casts are fossilized remnants of melted ice wedges, indicating past cold climates. The origin of ice wedges is explained by the thermal contraction theory, where repeated freezing and thawing cycles create vertical ice veins that widen into wedges over time.12

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permafrost
Active wedges, inactive wedges, and ice-wedge casts
Active ice wedges are those that are actively growing. The wedge may not crack every year, but during many or most years cracking does occur, and an increment of ice is added. Ice wedges require a much more rigorous climate to grow than does permafrost.…
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Active ice wedges are those that are actively growing. The wedge may not crack every year, but during many or most years cracking does occur, and an increment of ice is added. Ice wedges require a much more rigorous climate to grow than does permafrost.…
Read More