Stellar equilibrium is a balance between what two things?
1.outward gravity and inward heat
2.ourward pressure from light and inward pressure from heat
3. outward pressure from hydrogen and inward pressure from helium
4. outward pressure and inward gravity

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.