How has the relative ratio of igneous, sedimentary, and metamorphic rocks changed over Earth's history?

Question

Has the relative ratio of sedimentary over igneous rocks increased, simply as a result of more and more of the Earth's rock being exposed to sedimentary processes?Or has it increased only for the first billion years of Earth's history, and stayed fairly constant afterwards?

Answer 1

When Earth first formed, and for many years thereafter, the only rocks that existed were igneous ones that formed the initial crust. Once sufficient water vapor had been released and accumulated in the atmosphere precipitation (rain) commenced. The interaction between the igneous rocks and rain water led to chemical weathering of the surface rocks and mechanical destruction and transport of small pieces. The dissolved components were deposited as chemical evaporites and the solids as the first sediments. Continued exposure of larger portions of the crust through uplift led to more erosion and sediment formation.

Once the process of continental drift and plate tectonics developed, areas along the colliding edges of the primordial continets were uplifted and eroded while some of the crust was subducted leading to further igneous development. In the collision zone, pressures and temperatures were sufficient to initialize metamorphism. As the chemistry of the igneous magmas changed and sialic crust began to form, the average elevation of the crust increased, leading to further erosion and sediment erosion, transportation and deposition. This entire process was continually replicated around the world, resulting in a significantly increased amount of sedimentary and metmorphic rocks through time.