4) Once formed, convection currents bring hot material from deeper
within the mantle up toward the surface.
5) As they rise and approach the surface, convection currents diverge at
the base of the lithosphere. The diverging currents exert a weak
tension or “pull” on the solid plate above it. Tension and high heat
flow weakens the floating, solid plate, causing it to break apart. The
two sides of the now-split plate then move away from each other,
forming a DIVERGENT PLATE BOUNDARY.
6) The space between these diverging plates is filled with molten rocks
(magma) from below. Contact with seawater cools the magma, which
quickly solidifies, forming new oceanic lithosphere. This continuous
process, operating over millions of years, builds a chain of submarine
volcanoes and rift valleys called a MID-OCEAN RIDGE or an
OCEANIC SPREADING RIDGE.