Ice Hazards - "The Cracks": They can form ANYWHERE on the BAY
First thing we need to understand is the difference between a crack or pressure ridge... and ice splitting and drifting away known as a floe, also known as you're gonna have a bad day if you are on the wrong side. As most of you know, as ice builds, it expands. If there is ice from shore to shore, it does not have room to expand but cold temps dictate that it still must, so this is where we get pressure ridges. Pressure ridges come in 2 flavors: Overlapped & Folded.
Overlapped Pressure Ridge
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most common
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one sheet climbs over the other
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form fast with loud noise
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ice sheet breaks into loose pieces on either side of center
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weak plates of ice can extend 15' to either side
Folded Pressure Ridge
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ice sheets buckle into water
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difficult to spot
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water in middle quickly form skim ice
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swallow sleds, quads, trucks and people
Tectonic Crack
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commonly called an 'active crack' or 'working crack', generally does not grow, just opens and closes
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irregular shape, can be open in one spot and closed short distance away
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wind blown snow can form slush bands, water gets wicked up into snow
New Ice Holes
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usually round and form in groups around each other
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form during cold snaps and calm winds
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ring of white ice around them
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can be 1" to 4" thinner than surrounding ice
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can stay open water for days or a week following a cold snap as warm weather usually follows cold snaps
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if it snows after they skim over, they are a classic booby trap as their ice growth is hampered by the insulating snow
Sand Bar (reef) Holes
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water flowing over underwater structure causes ice erosion
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water under ice is 32 degrees F, water temp rises with depth, warmer water on bottom
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a sandbar like Saganing, Pinconning, Nayanquing & Rifle found on the Bay are classic thin ice traps