Image by kind permission GNS Science.
My children and I wanted to learn and understand more the nature of the Eddie (swirling pattern) in the photograph I took on the morning of Sunday 28th February 2010 after the Tsunami Alert for New Zealand had been issued.
I wrote and sent an e-mail to GNS Science on Monday, 01 Mar 2010 and recieved a wonderful reply and explanation from William Power that same day, thank you so much for your time and help.
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thank you for sending us a very interesting photo and video clip.
The swirl pattern that you photographed is caused by the mixing of muddy and clear water.
Since you were standing at the Pa in Mangonui what I suspect has caused this is:
A tsunami wave has carried clear water from Doubtless Bay into Mangonui Harbour with sufficient force to stir up the sand and mud in the harbour. The sea has then retreated carrying the now dirty water back out into Doubtless Bay. The dirty water mixes with clear water in the Bay, and around the boundary where this mixing occurs eddies are created. These eddies are the swirl patterns you observed.
Best Regards,
William Power
GNS Science
