Question

tectonic settings of igneous activity
the area below has five sites, labeled a, b, c, d, and e, where igneous activity has been observed. for each site, consider the igneous processes responsible for the activity, such as the type of plate boundary or other feature. possible choices are listed in table 1.
site a: a line of volcanic islands and submarine mountains. broad volcanoes on the islands are forming dark volcanic rocks. sample 1
site d: volcanoes on top of a mountain belt near the edge of the continent. the volcanoes erupt light - colored and gray volcanic rocks. older intrusive rocks, some with coarse crystals, are also exposed samples 5, 6, and 7
site b: circular volcanic depressions on land, which are filled with light - colored volcanic ash and light - colored volcanic rocks samples 2 and 3
site e: a chain of volcanic islands adjacent to an oceanic trench. the volcanoes erupt gray volcanic ash and lava flows. there are also some intrusive rocks samples 8 and 9
site c: a volcanic ridge that zigzags across the ocean floor. the rock sample is dark colored and is from a lumpy lava flow on the seafloor. sample 4
letter a is an example of a(n)?
(1) oceanic divergent
(2) continental rift
(3) ocean - ocean convergent
(4) ocean - continent convergent
(5) continental collision
(6) hot spot in an ocean
(7) hot spot in a continent

Explanation:

Site A describes a line of volcanic islands and submarine mountains with broad volcanoes forming dark - colored volcanic rocks. Ocean - ocean convergent boundaries often result in volcanic island arcs. In an ocean - ocean convergent setting, one oceanic plate subducts beneath another, leading to melting of the subducted plate and the overlying mantle wedge, which can cause volcanic activity forming island arcs.

Answer:

(3) ocean - ocean convergent