How might the chemistry and distribution of igneous rocks change in the future?Will it create more or less volcanoes?
We sort of have the question in reverse here; volcanic activity is the affecting force on the chemistry and distribution of igneous rocks. Igneous rocks are those fomed by magma, which comes from the Earth's second layer, the mantle. The magma is brought to the Earth's surface by way of vents called volcanoes. The location of volcanoes is linked to the placement of the Earth's tectonic plates, which can best be described as the outer layer of the Earth, the crust, broken into individual pieces. The boundaries between these pieces provide opportune areas for volcanic activity to take place.
The movement of some of these plates is fairly predictable. The movement in the long term is not as predictable. The composition of igneous rocks, given the chemical makeup of the magma from which they are produced, is not likely to change into anything radically new. It will depend upon the mineral makeup of the magma and the conditions it cools under as to the production of any given type of igneous rock.