Naked Science Forum

General Science => General Science => Topic started by: Emilio Romero on 25/06/2009 19:07:24

Title: are there underground tides?
Post by: Emilio Romero on 25/06/2009 19:07:24

If the moon’s gravitational pull affects tides, shouldn’t it also affect the huge amounts of water underground? And for that matter, can there be some kind of "tide" in the mountains that hold water inside?
 [???] [???]

thanks

Title: are there underground tides?
Post by: Ophiolite on 25/06/2009 20:00:03

There are tides in the solid Earth, not because it contains water, but because it has mass and so is attracted by the mass of the moon (and the sun), just as the oceans are. The magnitude of these tides is of the close order of 1 foot. As is often the case the Wikipedia article  (http://en.wikipedia.org/wiki/Earth_tide) provides a good starting point to learn more.

Title: are there underground tides?
Post by: Emilio Romero on 25/06/2009 20:32:26

thanks...
 
I copied this from the article

Earth tide effects
Volcanologists use the regular, predictable Earth tide movements to calibrate and test sensitive volcano deformation monitoring instruments. The tides may also trigger volcanic events. Seismologist have determined that microseismic events are correlated to tidal variations in Central Asia (north of the Himalayas).

.....
thus it can be the cause of a mayor earthquake also !!!???

Title: are there underground tides?
Post by: lyner on 25/06/2009 22:12:53

Water, being a liquid can move miles due to tidal forces. 'Solid' material flexes much less.
Some satellites ( can't remember which ones) in close orbits around giant planets are flexed so much by tidal forces that they have constant volcanic activity.

Title: are there underground tides?
Post by: Ophiolite on 26/06/2009 10:44:26

Quote from: Emilio Romero on 25/06/2009 20:32:26

thus it can be the cause of a mayor earthquake also !!!???

Perhaps. There have been a number of studies seeking a link between earthquake activity and lunar/solar tides. These have generally proved negative, though I recall reading some research pubished in the last two years that found a correlation. Unfortunately I don't recall where I saw this.

Edit:
Originally published in Science Express on 21 October 2004
Science 12 November 2004:
Vol. 306. no. 5699, pp. 1164 - 1166
DOI: 10.1126/science.1103961

Earth Tides Can Trigger Shallow Thrust Fault Earthquakes
Elizabeth S. Cochran, John E. Vidale, Sachiko Tanaka

Abstract
We show a correlation between the occurrence of shallow thrust earthquakes and the occurrence of the strongest tides. The rate of earthquakes varies from the background rate by a factor of 3 with the tidal stress. The highest correlation is found when we assume a coefficient of friction of µ = 0.4 for the crust, although we see good correlation for µ between 0.2 and 0.6. Our results quantify the effect of applied stress on earthquake triggering, a key factor in understanding earthquake nucleation and cascades whereby one earthquake triggers others.

Title: are there underground tides?
Post by: chris on 26/06/2009 12:22:52

Quote from: sophiecentaur on 25/06/2009 22:12:53

Water, being a liquid can move miles due to tidal forces. 'Solid' material flexes much less.
Some satellites ( can't remember which ones) in close orbits around giant planets are flexed so much by tidal forces that they have constant volcanic activity.

You're probably thinking of bodies like Enceladus, one of Saturn's moons, which follows an elliptical orbit and hence is subject to considerable tidal forces that cause stretching and squeezing of the moon sufficient to trigger what's been dubbed "the biggest geyser in the solar system" - a plume of material that shoots thousands of miles out into space and even contributes to one of Saturn's rings.

http://www.thenakedscientists.com/HTML/content/interviews/interview/716/
http://www.thenakedscientists.com/HTML/content/news/news/333/

A paper published this week (June 24th) in Nature has found evidence for sodium (salt) in the plume, suggesting that the source is a giant sub-surface ocean kept warm and liquid by the tidal effects:

http://www.thenakedscientists.com/HTML/content/news/news/1741/

Chris

Title: are there underground tides?
Post by: lyner on 26/06/2009 12:29:37

That's the one, Chris. The surface is kept warm in that way. Not a good place to live tho'.

Title: are there underground tides?
Post by: LeeE on 26/06/2009 13:49:17

I think the effect is more dramatically shown with Io, and that may have been the one you were thinking of, although Enceladus is believed to have a liquid water 'ocean' below its outer layer of ice, so I guess it could be regarded to have sub-surface tides.

Title: are there underground tides?
Post by: Emilio Romero on 26/06/2009 14:23:49

here's another one... with a grain of salt
(Sodium traces hint at subsurface ocean on Enceladus)

http://www.nature.com/news/2009/090624/full/news.2009.596.html

Title: are there underground tides?
Post by: Andrew K Fletcher on 26/06/2009 17:03:52

http://www.thenakedscientists.com/forum/index.php?topic=1929.0

Title: are there underground tides?
Post by: lyner on 27/06/2009 12:58:17

I know this is asking for it but, which bit of that thread is relevant here, AKF?

Title: are there underground tides?
Post by: Ophiolite on 27/06/2009 13:45:39

Quote from: sophiecentaur on 27/06/2009 12:58:17

I know this is asking for it but, which bit of that thread is relevant here, AKF?

I was thinking exactly the same thing, then decided I didn't want to know.

Title: are there underground tides?
Post by: Emilio Romero on 27/06/2009 15:34:48

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.freesmileys.org%2Fsmileys%2Fsmiley-confused005.gif&hash=32cfa2a895a9b7f0c1223a34d6f4ccf4) (http://www.freesmileys.org/smileys.php)