Transcript of Rock Cycle

[music] Wherever you walk on Earth’s surface,   you’re likely at some point to see rocks cropping  out of the ground. Each rock tells a story of what   happened in that particular location during  Earth’s past history. To read these stories,   we need to read the rocks, just like books; we  need to learn how to identify and understand   the meaning of the words and pictures within  them. The words and pictures in a rock are the   physical and chemical characteristics and the  basic building blocks of most rocks: minerals.   All rocks on Earth’s surface can be  classified as one of three kinds:   sedimentary, igneous, or metamorphic. Sedimentary rocks are those formed from   the compaction or cementation of debris that has  collected in low-lying areas on Earth’s surface,   like sands buried in sand dunes, or rocks  that formed through the precipitation of   minerals from fluids at or near Earth’s  surface (like when seawater evaporates,   and salt crystals are left behind). Igneous rocks are those that formed after   molten magmas or lavas cool and solidify. Metamorphic rocks are those that have   changed chemically or physically due to  increased temperatures and/or pressures   Once any of these rocks forms, it can and will  change with time. When you pick it up to study it,   you’re seeing it at only one moment in  time, and you look for the evidence of   its most recent history. Sometimes you can  see deeper into its history. For example,   imagine that a shallow seabed evaporates and  leaves behind salt crystals (a sedimentary   rock). The setting is a warm dry climate near the  ocean. Over time, these rocks can get buried and   heated up and put under pressure where they  then change or metamorphose into a new rock.   Now the setting is deep under a continent.  If buried deep enough and heated up enough,   the entire rock can melt to form a magma,  which if erupted and cooled and solidified,   becomes an igneous rock. Now we are at the  surface of an erupting volcano. Over time,   the lava flow will break down (weather) and  small pieces will collect in low-lying areas   such as river beds and after being buried by other  sediment can have percolating waters cement the   grains together to create a new sedimentary rock. When we later find this rock on Earth’s surface,   we use chemical and physical clues in the rock  to peer into its complex history. One of the most   important clues we’ll look for are the minerals  and textures within the rock. To start the journey   of reading the stories of rocks, we have to start  with learning how to identify minerals and what   they tell us about a rock.   Pause now. [music] For more information and more detail, continue  on to the next video in this series. [music]