In article ,
Morenga wrote:
Does the gravity force only work unidirectional (towards the center of the
earth)...

Earth's gravity is not directed *precisely* toward its center, because
of complications like its equatorial bulge. But that's not quite what
you really wanted to ask...

or can outside forces (like the moon or the redistribution of ice/water
masses) also
alter the distribution of mass inside the earth ?

Only very, very slightly.

There are tides in the solid Earth as well as in its oceans, because on a
planetary scale there is no such thing as a rigid material. But they are
quite small, and their effect on Earth's mass distribution is minute.

Similarly, redistribution of water (and air) changes Earth's mass
distribution enough to be detectable, but in absolute terms the effect is
extremely small.

Are there any known effects of the variations of earth distance from the sun
on the distribution of mass inside the earth?

Solar tides are a bit stronger when the Earth is closer, but otherwise no.

also read that moon vulcanism is caused by these grav tides.

There is no known vulcanism on the Moon today. Except for meteorite
impacts, the Moon appears to have been a very quiet place, geologically
speaking, for the last couple of billion years.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |