Une colonia au Texas 500 000 Texans, souvent d'origine latino-
américaine, vivent dans plus de 2000 colonias
à moins de 100 km de la frontière mexicaine.
D'où viennent ces habitants ? En quoi cette
photographie montre-t-elle les limites de la
prospérité ?

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. 

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen

Explosive eruptions are the most hazardous, involving large volumes of tephra and gases emitted from the volcano. lahars, pyroclastic flows, ashfall, and many other volcanic hazards are commonly associated with explosive eruptions. explosive eruptions are very dangerous. basically, any form of hazard can occur.