Data collected by the drilling ship glomar challenger confirmed that

Data collected by the drilling ship Glomar Challenger confirmed that none of the ocean floor is more than about 180 million years old.

Glomar Challenger began drilling on both sides of the mid-ocean ridges to gather data. The data confirmed what the sea-floor spreading hypothesis predicted. The ocean floor is youngest along the central valley of the mid-ocean ridge while the ocean floor in subduction zones or near the edges of the continents is oldest. The data has confirmed that none of the ocean floor is more than 180 million years old because the older oceanic rock will undergo subduction and go back to the earth's mantle.

Mantle convection is the process that drives plate tectonics. the theory of plate tectonics states that the crust is divided into plates that float on the semi molten mantle below. the circular motion of the magma as it slowly rises and falls or move though convection cells drags the plates along causing them to move. the heat source in the lamp would represent the earth's core. the core is the source of energy that drives convection in the mantle. the lava represents molten magma under the earth's surface. if the lava lamp had floating pieces they would move as the circular motion of the lava in the lamp as it rises and falls would move them along the surface. these floating pieces would represent pieces of the earth's crust. 

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.