When icebergs break apart due to melting or other reasons they make a lot of noise and cause massive movements of ice shaking the surrounding area but does that mean we should label the shaking event an Earthquake? Well consider a glass cup on the counter and you have probably already had this happen. You have your drink in the cup and it could be water, Koolaid, Soda or better yet a "White Russian" and you can be across the room as the ice melts it makes a sound as it slips inside the cup. Now a strong glass cup you would hear the noise but of course the cup would not move much now would it? No it wouldn't, well maybe a little but probably not you see. But if you had a paper cup the shift could move the paper cup a little as the water sloshed. If you were to take several cups and set them on a smooth surface and trace around the cup base you could measure the amount of movement. You could also measure to what degree the cup shaked the surface if you had proper instrumentation. This subject recently came up in an online think tank when one member Swift from Las Vegas asked; "Ice is not necessarily occurring to the bottom of the ocean floor, so how could these be labeled "earthquakes" when most icebergs don't go to that depth? Just curious." So then if the displacement of the movement of the water moved the whole cup, even slightly then yes you would have an Earthquake. However if it was just a loud sound you would have sound waves traveling through the Earth, which might mimic an Earthquake wave but it would not actually be an Earthquake unless you had actual Earth movement you see? The rapid compression of the density of the liquid could also be measured on the bottom of the surface of the cup its self to see if that pushed down onto the bottom of the cup. Remember the waves of the event of a rapidly dropped ice cube would move in all directions including down, but much faster along the surface which would continue if they hit land in any direction. Perhaps the biggest notice would be the movement of water and not the actual shaking of the ground, however how you classify the changes would determine if you would consider this an Earthquake or not I would assume. |
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