Rock Cycle

GOOGLE:    Interactive Rock Cycle

Reading Activity

SC.7.E.6.2: Identify the patterns within the rock cycle and relate them to surface events (weathering and erosion) and sub-surface events (plate tectonics and mountain building).

Rock Cycle Patterns The Earth formed about 4.6 billion years ago, along with the other solar planets and the Sun itself. The planets built up by accretion of rocky and gaseous debris (steroidal, planetesimal [meteoritic] materials and comets) through collision of orbiting bodies. Aided by gravitational attraction which helped to compact these material, early on the assembling Earth underwent partial to complete melting, separation of different materials into an inner and outer core (Iron-Nickel), an extensive interior mantle, (Iron/Magnesium/Calcium-rich silicates), and a thin crust (enriched in Silica, Sodium/Potassium/Aluminum), all (except the outer core) solidifying by cooling over the first few hundred million years; escaping gases produced an atmosphere (principally H, CO2, N, CH4) were held above the solid Earth by gravity owing to its large mass; in time (about 4 billion years ago), the Earth’s exterior cooled sufficiently to allow vast volumes of water vapor to condense, forming in lower areas great concentrations of water collected into depressions (oceanic basins). The Earth’s materials are diverse and variable. Most variation occurs in the outermost 200 kilometers, in the lithosphere. Igneous rocks form directly by crystallization of hot melts made up of silicates (SimOn) combined with Fe, Mg, Ca, Al, Na, K, Ti, and H2O). Minerals formed from these make up nearly all the mantle and crust. Rocks at the surface decompose/disintegrate by reaction with the atmosphere/hydrosphere to produce solid debris and soluble chemicals that are transported/deposited to form sediments, that upon burial are converted to Sedimentary rocks (usually layered; strata). Previously formed rocks that are heated and pressurized when buried to shallow to moderate depths (5 to 70 km) of the crust recrystallize as solids under increased temperatures and pressures to form Metamorphic rocks (some may melt). The above processes comprise the Rock Cycle, shown below, and discussed in more detail on this page.