Annual temperatures in north america typically reach their maximum at the end of july, and not during the june 21st solstice when insolation is greatest. why is there this "lag" of more than a month between maximum insolation and maximum air temperatures?

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. 

Magma is outside the volcano  and lava is inside the volcano. 

Ithink i might know wait one second let me serve

Iwould say the answer is: trade windshope that : )