Depending on type of sediment produced different types of metamorphic rock. Meteorites represent broken material from other planetary material. When it hits, moving at enormous velocity, melts where it hits. Frictional heat created and makes black rock: relative dating: key principles. Relative dating = rocks placed in proper sequence of formation. Laws still hold with folding, just need to see it. Younger features cut across older features: younger features ex dykes, faults, older ex pre-existing rocks. Fragments of one rock that has been enclosed within another. Rock containing the inclusion is younger than the inclusion. Break/gap in rock record caused by erosion and/or non-deposition of rock units. When no break in rock record = conformable. Unconformities represent significant geologic events in earths history, an enormous amount of time. Angular unconformity: tilted rocks are overlain by younger, flat-lying rocks. Disconformity: strata either side on the unconformity are parallel, gap in time.