B REFLECT & DISCUSS The Vishnu Schist has a numerical age of about 1700 million years. The Lower Cambrian Tapeats Sandstone was deposited on top of the unconformity that you considered in part A. Imagine that you find reliable information indicating that the Tapeats Sandstone was deposited at the very start of the Cambrian Period and then how about much time is represented by the rock record that is "missing" across this unconformity—missing in the sense of erosion, nondeposition, or both prior to deposition of the Tapeats Sandstone on the erosional surface at the top of the Vishnu Schist?

During metamorphic processes, increased pressure and temperature can affect the of minerals in rock. rocks subjected to very high pressure are typically than others because mineral grains are squeezed together, and the atoms are more closely packed. during metamorphic processes, water facilitates the transfer of ions between and within minerals, which can the rate at which metamorphic reactions take place. the growth of new minerals within a rock during metamorphism has been estimated to be about per million years. metamorphism is commonly associated with convergent plate boundaries, where two plates move toward each other. during contact metamorphism, a large intrusion will contain thermal energy and will cool much more slowly than a small one. metamorphosed sandstone is known as the metamorphic rock made from metamorphosed shale, was once used to make blackboards for classrooms