What is the correct term for changes in the elliptical shape of earth’s orbit every 100,000 years?

Milankovitch cycles is the correct term for changes in the elliptical shape of Earth’s orbit every 100,000 years.

Milankovitch cycles are the various influences of the earth's movements on its climate over thousands of years. There are three dominant Milankovitch cycles which are eccentricity, axial tilt, and precession, that combines to affect the location of solar energy around the earth, seasonality, and eventually influence climatic patterns.

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.