Gravity then caused abundant, dense iron to sink toward the Earth's center, forcing less dense material to the surface.
(Gravity; caused; abundant, dense iron to sink toward the Earth's center; T:then) Context(Gravity caused,List([0, 19))):(abundant, dense iron; to sink; toward the Earth's center)
Gravity caused,List([0, 19))
Gravity abundant, dense iron
caused to sink
abundant, dense iron to sink toward the Earth's center T:then
toward the Earth's center