Ash flows are usually associated with felsic volcanoes, not mafic volcanoes. Quartz and potassium feldspar are excellent examples of metamorphic index minerals because they are only found in high grade metamorphic rocks. The crust, mantle, and inner core are all solid, but the outer core is liquid. Absolute geologic time is measured in terms of years, whereas relative geologic time is measured in terms of the relative ordering of events. The Neptunists thought that igneous rocks precipitated out of sea water, similar to the way sugar will precipitate out of sugar water if the solution is left to evaporate.
Metamorphic rocks form only by an increase in temperature.
Metamorphic rocks and igneous rocks can erode to form sedimentary rocks, but sedimentary rocks cannot erode to form more sedimentary rocks. The Cascade volcanoes in the Pacific Northwest are a good example of a subduction-related volcanic arc.