Which one of these events could potentially change the length of the day?

The length of a day is determined by the rotation of the planet. Among the four events listed, an earthquake of sufficient magnitude could do this; the others cannot. A recent example of is the earthquake that struck northeastern Japan in 2011. The amount of mass moved by the earthquake was so large that it shifted parts of Japan by about 4 metres, moved the figure axis of the Earth by about 17 centimetres and accelerated the rotation of the Earth. As a result of the mass shift and the acceleration that followed, the length of an Earth day was shortened by 1.8 microseconds.

More Info: www.nasa.gov

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70 Comments

Barb Lawson

Darn.....I am going to miss that 1.8 microseconds of daylight.

Biswadev Roy Ghatak

Excellent question and very clear explanation, thanks!

Sid Brechin

Did not know that did know an eruption could change hours of daylight. Most profound example being Krakatoa in the late 1800s

tdelisi

Sorry for my bluntness, but the question was not vague, but your comprehension and interpretation are at fault. You say "I took it as how it would affect day light hours", but the question asks about the length of the day. It is your fault that you could not discern the difference between the meanings of a length of a day versus the length of one of its components = daylight. Part of our human development, and our intelligence is the ability to make these types of critical distinctions.

Wayne Roberts

But if the Earth is flat, how can the rotation be effected???

George Edmund Bradfield

I didn't know this fact...but it makes more sense than the other suggestions. I was wondering how the concept of Daylight was conceived in the extreme Northern and Southern areas of planet earth.

Lindy Carmalt

Aha - 1.8 microseconds - that explains why most of us hadn't noticed the difference . . .

EIFEL

Yes

Nancy Cobb

Interesting, but what was the most violent volcano that was ever recorded?

Albeck1994

No it was still the same length just less daylight

Albeck1994

No the day is still the same length just less daylight hours

Albeck1994

So you never heard of the 2011 earthquake in Japan. Or read the explanation. Oh it's continents btw and they're still moving.

Marilyn Gil de Arronte

That's the best questions. .of course 100%

Carole Anderson

i did not know this but got it right.....not so much by pure guessing but it seemed like the logical answer since an earthquake could potentially alter the shape of the earth