Ice circles are a natural anomaly known to rarely occur in very cold climates. Scientists speculate that they are formed from whirlpools that rise to the surface and then freeze in the shape of a perfect circle. The largest reported ice circle was measured at 150 meters in diameter. I have seen this once - it was unbelievably, perfectly round.
Jade Iceberg, Antarctica. When seawater at depths of more than 1,200 feet freezes to the underside of massive ice shelves, it forms ‘marine ice.’ Enormous hunks of ice break off from the ice shelf, creating icebergs. When one of these icebergs overturns, its jade underside is revealed. The wondrous color of this ‘marine ice’ results from organic matter dissolved in the seawater at those great depths. Green icebergs are infrequently seen because their verdant bellies are underwater