Question

along the west coast of south america, a line of volcanoes appears at the convergent plate boundary. which process explains the formation of volcanoes?
usgs
explanation
divergent plate boundaries: where crust is generated as the plates pull away from each other.
convergent plate boundaries: where crust is consumed as one plate dives under another, creating volcanoes and mountains.
transform plate boundaries: where crust is neither produced nor destroyed as the plates slide horizontally past each other.
plate boundaries: zones - areas between plates in which interactions take place.
volcanic and earthquake boundaries
a. continental rift where two plates move apart
b. one plate sliding past another causing friction and melting
c. melting of the crust because plates are moving over a hot spot
d. subducting of one plate under another causing melting of the lower plate

Explanation:

To determine the correct option, we analyze each choice based on plate tectonics concepts:

• Option A describes a divergent boundary (plates moving apart), not related to convergent boundaries where volcanoes form due to subduction.
• Option B describes a transform boundary (plates sliding past each other), which doesn't involve melting for volcano formation.
• Option C refers to hotspots (like Hawaii), but the question is about convergent plate boundaries (e.g., Andes in South America), so this is incorrect.
• Option D: At convergent boundaries (oceanic - continental or oceanic - oceanic), one plate subducts (is forced) under another. The subducting plate (usually oceanic) descends into the mantle, where high pressure and temperature cause it to melt. This melted material (magma) rises to form volcanoes. The Andes are formed at a convergent boundary (Nazca plate subducting under South American plate), so this explains volcanic formation here.

Answer:

D. Subducting of one plate under another causing melting of the lower plate