This Week’s Supermoon Did Have One Effect: Flooding.
But tides work with the cube of distance, so if the Moon is 10 percent closer the tides are 1.1 x 1.1 x 1.1 = 30 percent higher than when the Moon is farther away. The higher high tides we get when the Moon is close are called proxigean tides, and they happen every month. The unusually close Moon on Nov. 14 meant they were somewhat higher than normal, even for regular proxigean tides.
But there’s more. The Sun creates tides on the Earth, too. It’s far more massive than the Moon, but much farther away, so in the end contributes about half as much to the tides on Earth as the Moon does. When the Moon and Sun are in a line these forces all add up, creating even higher high tides (and lower low tides) than usual. We call these “spring tides”, and they happen twice a month, when the Moon is full and when it’s new.
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So the “Supermoon” pulled a double whammy: It was closer than usual, and full, so tides were especially high earlier in the week. We had, and still this week are still having, proxigean spring tides.