Final answer:
The assignment involves sketching a cross-section of tectonic plates from Pacific to South America and labeling key features such as the subduction zone, rift, rock types, and respective scales. The sketch starts with a rift zone at the Pacific Plate, through a subduction zone at the Nazca Plate, and ends with the South American continental plate.
Step-by-step explanation:
Your assignment requires you to create a graphical representation of the tectonic plates from the Pacific Plate, crossing the Nazca Plate, onto the South American Plate. Beginning from the west (Pacific Plate), we encounter a rift zone represented by the Mid-Atlantic Ridge. Here, the plates are moving apart due to upwelling currents causing the mantle to convect, and molten basaltic rock rising to the surface forms the new crust.
As we move east towards the Numerical Plate, we observe a subduction zone. This is where the oceanic plate subducts or is forced down into the upper mantle due to convergence with the continental South American Plate. The subduction process creates high pressures and temperatures causing the subducted plate to melt and forming a volcanic arc. Besides, the area right at the subduction zone is marked by an ocean trench.
The South American Plate is the final stage of your cross-section. Here, you will draw the continental plate with marked mantle, crust, and lithosphere.
Now, to fulfill the remainder of the assignment requirements, include a distance scale (in kilometers) and a depth scale (in kilometers) to represent the different depths of the crust and the mantle. For the igneous rocks, label basalt at the ridge (extrusive) and both andesite and diorite at the volcanic arc (andesite being extrusive and diorite being intrusive).
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