Answer to Question 1
Answer: The principle of isostasy is the state of equilibrium between the buoyant force of the asthenosphere and the downward force of gravity. The lithosphere floats on the denser mantle. Because the pressure exerted on the mantle by the lithosphere must be the same at any given depth, the lithosphere adjusts its position until a state of equilibrium is achieved. The thicker (but less dense) continents stand higher on Earth's surface and extend deeper into the mantle than the thinner (but more dense) ocean basins. Seismic waves reveal the extension of continental and oceanic crust into the mantle.
Answer to Question 2
Answer: Fluids enclosed in pore spaces act as a catalyst to aid metamorphic reactions. When a rock is subjected to increased temperature and pressure, the amount of pore space decreases and fluid is squeezed out. Fluids readily react with the surrounding rock. In general, the more fluid, the faster the reaction.
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