At what location does gravity play a role in moving tectonic plates

In subduction of one plate over another on the basis of weight

Explanation:

When two plates moving and colliding, the plate with higher mass will subduct below the plate with lower weigh and lighter would remain above. generally continental types of plates are lighter in weight and oceanic plates are heavier.

Ex:- The collision of Eurasian plate and Indian plate. Indian plate is below and Eurasian plate above and formation of Himalaya

their crystal patterns have been disrupted by stress

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west