For example, most “full view” iceberg pictures I’ve seen, the iceberg has been vertically oriented – if ice is less dense than water, wouldn’t it at least be horizontal, with more than 10-15% of the mass visible above water?
In: Physics
The density of ice is about 90% that of water. That means that, if you attempted to fully submerge the iceberg (assume for a moment that you can), whatever volume of water the iceberg displaced, the water would push back with a bouyant force of ~110%* the weight of the iceberg. That forces the iceberg up a bit, until there is equilibrium, where the submerged portion of the iceberg elicits enough bouyant force from the water to balance its weight.
To think about it more intuitively, contrast this with a bag of air that you attempt to fully submerge in the water. The bag is going to eventually just float on top of the water surface, unsurprisingly because its density is just 0.1% that of water. Put a weight in the bag of air and it will submerge a little more. Add more weight until the average density of the bag matches that of ice, and you’ll find that only about 10% will be submerged, like an iceberg.
* This happens because, whatever *volume* of fluid you displace, the surrounding fluid will push back with enough force to support the *weight* of the missing fluid. This phenomenon is why hot-air balloons and helium balloons can float.
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