Read the two passages. First explain how the central theme is similar in both passages. Then discuss how the passages present that theme in different historical or cultural contexts. Passage
Passage 1:
Isaac and Jed were inseparable growing up in the backwoods of the Kentucky-Tennessee border. They would spend all day chasing squirrels and building forts from fallen trees. As America approached the Civil War, though, it became clear that the boys' families fell on different sides of the conflict. Isaac's family supported the South, and Jed's family supported the North, and soon the boys' parents forbade them from spending time together. When war finally broke out, both families pushed their sons to enlist. In one critical battle, Isaac and Jed even fought against each other. Though both were fortunate enough to survive the war, Jed moved to Albany and Isaac settled in Atlanta, and the friends never crossed paths again.

Passage 2:
Carla and Dee met on the first day of college and quickly became closer than sisters. They took all the same classes and even visited each other's homes during school breaks. They both majored in computer science and specialized in designing computer games. When they graduated, they desperately tried to find jobs together but could not. They went to work for rival video game companies, and each began developing a game they had thought of together: Zombie Soccer. Both rushed to complete the project first, and since the companies were very secretive, the women pretty much stopped speaking. Carla's game was released first, but Dee's was more popular. They had dinner together shortly after the games were released, hoping to reconnect, but they found that they had both grown closer to their coworkers than they were to each other

The diaphragm is what i think ur talking about

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.