Heat supplies the energy that causes motion. The deeper you go into toward the Earths core, the hotter it gets. At the core it is really hot. All that heat tries to rise toward the surface. In the Mantle, the rock is partially melted and is able to move. As it is heated, the material in the mantle moves toward the surface. As the mantle material rises, it cools. When it reaches the Earths crust, it is mostly stopped. A little of the material can break through the surface, but not all. Instead, it begins to move horizontally. The mantle material moves horizontally away from a mid-ocean ridge crest. Toward the surface, the mantle material starts to cool. As it cools it sinks back down into the mantle. These areas are where deep sea trench occur. The material sinks back down to the core. The system operates like a giant conveyor belt. The motion due to heating and cooling is called convection.

What kind of feature occurs where cooled mantle material sinks back down into the mantle?

Allan sat down at his desk and pulled the chair in close. Opening a side drawer, he took out a piece of paper and his inkpot. After filling his pen, Allan looked at his paper in the orange glow from the lantern set back in the desk's right-hand corner. His pen cast a forbidding line of shadow slanting across the page, echoing the inky darkness crouching in the edges of the lantern's struggling glow. The only other illumination came from a lurid moonlight filtered through thin branches and clouds, casting its bone-pale glow onto the pine floorboards. Allan unfolded another page, this one crowded with ranks of letters in tight formation from left to right. The lines of letters stepped into their divisions, in the shape of a story's outline: the loose, dry skeleton of a tale lay exposed beneath their feet, awaiting tendons, muscle and blushing skin. Allan reviewed the troops, all prepared to disembark, their task to form the tale of a young man returning home from Life Abroad to find his childhood friend a bride to-be, thus upsetting the apple cart of his life's plan, clarified of course by his very time away from her he loved best. Although the concept was a simple one, Allan thought it had potential. Besides, the public liked a good, simple romance. Perhaps this will be more saleable, he thought and began to write. They gazed at each other, lost in the rapture of love based so deeply within their hearts that they had never seen it before. "What about Roger?" she asked, knowing that the answer no longer mattered.

What steps did Allan take before writing?

I had drunk too much, I confess, though we all had. Somehow, Tasha and I began to argue the worth of Solevgrad jazz, as inconsequential a topic as I can imagine. She had studied it in school, so she thought herself as an expert. I once had a neighbor who played it constantly, loudly, and badly, so I thought I knew it better. Malaquez tried to mediate, but I saw him as siding with Tasha. So, I think, did she. The subject shifted from music to Tasha's obsession with fame, undoubtedly by a leap that I made. She had no choice but to follow. (I do not remember any of this well, just now, nor do I care to. Those who are truly curious may look at the last act of "Captured Moments.") I remember suggesting, with characteristic tact, that she add Emil to her small list of major accomplishments. Malaquez glanced away, embarrassed. Tasha looked at me as if to say, "I will." She said, "I feel sorry for you, Nardo. I'll see Emil home." "Yes," I said, "Do that," and did not care what she did, or why. Emil asked, "You're all right?" I muttered something he must have interpreted as assent. They both walked up to Emil's home while I watched the scarlet moonlight ripple on distant waves. Disgusted with Tasha but more disgusted with myself, I finally realized she would not return that night and went into The Sleeping Flamingo to drink myself to sleep. She had not come home when I woke in mid-morning.
According to Nardo, who did Tasha feel took her side of the argument?