What is the most likely cause of initial melting at Site D?A) Temperature IncreaseB) Pressure DecreaseC) Addition of Volatiles Rock 3. This brown-colored rockRock 1. This rock isdark colored, has novisible crystals, andis not glassy. It doeshave many vesicles(holes) and is a vol-canic rock. A chemi-Rock 2. This light-colored rock is finely crys-talline and not glassy. It contains some fine-grained gray crystals and a few small holes.A chemical analysis documents that it is afelsic rock. It was collected on a volcano.contains large, light-colored lenses offlattened pumice in a finely crystallinematrix. Under the microscope, thematrix contains compacted volcanicash, along withsmall crystals andfragments of otherrocks. The crystalsare mostly quartzand K-feldspar.cal analysis revealeda relatively low silicacontent.Rock 4. This rockis finely crystallineand lacks visiblecrystals. It has adark-gray color. Achemical analysisof the sampleindicates that itis a mafic rock.Rock 6. This rock2has very large crys-tals, some of whichare 5 to 10 cm long.Most of the rockis K-feldspar andquartz, and the darkcrystals are a typeof amphibole thatis most common infelsic rocks.4Rock 5. This porousrock in the centerof the photographhas numerous holesand is extremelylightweight. It islight colored and iscomposed of vol-canic glass. Thereare no visible crys-tals, but the rock islikely to be felsic incomposition.Rock 9. This rockcontains large crys-tals of K-feldsparin a brown-coloredmatrix of smallto medium-sized7.8.crystals. There isno glass, ash, orRock 7. This medium-grained rock is a plutonic rock. It has aRock 8. This rock has scattered visible crystals ofsalt-and-pepper appearance, caused by the presence of felsic amphibole and biotite in a medium-gray, finely crystal- vesicles, so the rockminerals (feldspar and quartz) and mafic minerals (mostly bio-tite mica). It is intermediate in composition.line matrix. It reportedly was collected either on a vol- is probably not acano or from dikes exposed near a volcano.volcanic rock. Site D: A continental magmatic arc,where volcanoes are on top of amountain belt nearthe edge ofthecontinent. The volcanoes erupt light-colored and gray volcanic rocks.Older intrusive rocks, some withcoarse crystals, are also exposed.[Samples 5,6, and 7]Site A: A line of volcanicislands and submarinemountains. Broadvolcanoes onthe islands are foming darkvolcanic rocks. [Sample 1].Site E: An island arc,Site B: Circularvolcanic depressions(calderas) on land,which are filled withlight-colored volcanicash and light-coloredvolcanic rocks.which is a chain ofvolcanic islandsadjacent to an ocearictrench. The volcanoeserupt gray volcanicash andlava flows.There are also some[Samples 2 and 3]intrusive rocks.[Samples 8 and 9]Site C: A mid-oceanridge that zigzags across the ocean floor. The rock sampleis dark colored andis from a lumpy lava flow on the seafloor. [Sample 4]

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Site D is a continental magmatic arc where…

What is the most likely cause of initial melting at Site D? A) Temperature Increase B) Pressure Decrease C) Addition of Volatiles