The fact that the earth crust is floating in the mantle over a sea of magma
And how much it floats or sinks is directly linked with local gravity...
gravity that is a reflect of the thickness of the crust in that area. Or if we prefer of how much matter is accumulated in that local area.
The thicker, the heavier, so the crust will sink more by the force pointing down that come from its own weight and local gravity in the area will increase
...
Can you see yet where this is leading us, and why I'm 120% sure that climate change WILL come with an increase in volcanic eruptions?