Complex sentence: As the crust is stretched it thins just as a stretched rubber band would, the thinning crust subsequently subsides over time relative the thicker undeformed crust by gravitational equilibrium or isostasy.
Split into simpler sentences: As the crust is stretched it thins just as a stretched rubber band would. This thinning crust becomes subsequently subsides over time relative the thicker undeformed crust by gravitational equilibrium or isostasy.