This weekend there will be a Super Moon. On June 23rd, the Moon becomes full at essentially the same time it reaches perigee (the closest to the earth). This near-perfect coincidence makes the Moon “super.”

One question,

Will the extraordinary tides from the super moon trigger a mega earthquake?

This weekend’s full Moon is a “supermoon,” and will appear as much as 14% bigger and 30% brighter than other full Moons of 2013.

Saturday evening, the moon will rise at approximately 8PM, give or take 15 minutes around the U.S., and will set at around 5AM.

Sunday evening, the moon will rise around 9PM and set around 6AM.

The best time to observe the super moon is just after sunset on Saturday night, but anytime this weekend will be startling. Just walk outside and look to the east…

When the moon is closest to the earth it brings with it extra-high tides. In most places, lunar gravity will pull tide waters an inch or so higher than usual. Local geography can amplify the effect to as much as six inches.

Now imagine this… the additional weight of sea water pressing against the earth, up and down the coastlines during the super moon… while at the same time magnifying the stress between the added weight versus the subtracted weight of where that water came from…

On average, sea water weighs about 64 pounds per cubic foot,
(equivalent to a strip of water 1,728 inches long by 1-inch wide by 1-inch deep).

The U.S. lower-48 has approximately 9,000 miles of coastline.

There are 63,360 inches of coastline per mile. At 1-inch wide by 1-inch deep, that linear mile of sea water weighs 2,347 pounds.

That’s 21,120,000 (21 million) pounds for every 1×1 inch of water that extends out from the entire length of the lower-48 U.S. coastline.

That’s 1,338,163,200,000 (1.3 trillion) pounds of added weight for every mile of 1×1 inch of water that extends out from the entire coastline.

How many miles does the tidal bulge extend from the coastline during a given high tide?

In the example above using the U.S. coastline as a measure of relativity, in reality the tidal bulge is huge, and exists regardless of the coastline as a measure. The bulge travels around the earth’s oceans while it maintains it’s alignment with the moon while the earth rotates (see explanation below).

Are you getting the picture of the staggering amount of weight that is applied on the crust of the earth during an event like this?

Sure, tides happen several times a day. A super moon occurs about once a year.

One wonders if the extraordinary crustal stresses of a super moon event will increase the risk of earthquakes, or even a mega-quake due to the magnitude of additional weight that will be pressing down during this time.

I suppose we shall find out this weekend…


About Tides…

image: Oceanography 10, T. James Noyes, El Camino College

There are two bulges in the ocean, places where the sea surface is higher than normal, on opposite sides of the Earth. One bulge points towards the Moon, and the other bulge points away from the Moon. The water that makes the sea surface higher at the bulges comes from the other 2 sides of the sides of the Earth (it has to come from somewhere) which lowers the sea surface at these locations. The 2 places where the sea surface is higher are, of course, experiencing high tides, and the 2 places where the sea surface is lower are experiencing low tides.

image: Oceanography 10, T. James Noyes, El Camino College

Two bulges in the Earth’s ocean results in 2 high tides and 2 low tides per day, with 6 hours between high and low tide. Each day, the Earth rotates on its axis (spins all the way around 1 time). The bulges, on the other hand, stay facing the Moon and facing away from the Moon as the Earth turns underneath. As a result, every location on the Earth goes into a bulge (high tide), then out of the bulge (low tide), then into the other bulge (high tide), and then out of the bulge (low tide). Thus, each location on the Earth experiences 2 high tides and 2 low tides per day. It takes 24 hours (1 day) for the Earth to turn all the way around, so it takes 6 hours for the Earth to turn a quarter (one-fourth) of the way around and therefore for a locatio n to move from a place in a bulge (high tide) to a place outside a bulge (low tide) or vice versa.

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