The Rock Cycle | GEO GIRL — Transcript

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1. 0:00today we're going to be talking about the rock  cycle now this is a short episode but important
2. 0:05one so let's jump right in the rock cycle this  title page actually i included an animation
3. 0:13showing that this is a cycle so you can  see the arrows around the outside are
4. 0:18going in a circle but there are also arrows  in the middle and that kind of shows that
5. 0:22whichever type of rock that you land on which  we'll talk about in a second it can kind of
6. 0:27go to whatever next part of the cycle it wants to  it doesn't have to go in an order so that's a big
7. 0:32thing about the rock cycle it can go out of order  but it is a cycle and it's really fundamental to
8. 0:38earth's processes and how earth functions before  we start i'm going to introduce rock types there
9. 0:44are three main rock types igneous sedimentary and  metamorphic and we'll be talking about these a lot
10. 0:50more in later episodes but first i just wanted  to show an initial picture and you'll understand
11. 0:57why these look the way they look by the end of  this episode hopefully in terms of the rock cycle
12. 1:03people generally start talking about the cycle by  talking about cooled magma or igneous rocks which
13. 1:10then can be weathered and eroded into the trital  sediment just broken up igneous rocks and this
14. 1:16sediment can be re-compacted to form sedimentary  rocks and from deep burial and heat and pressure
15. 1:23of the sedimentary or igneous rocks themselves  that can cause metamorphism forming metamorphic
16. 1:29rocks now that was just a very brief intro to get  a little bit more in depth we can talk about the
17. 1:35different pathways in which these things occur  this is a cross-sectional view of the subduction
18. 1:41zone showing the rock cycle in a different way  just to get a little bit more applicable to earth
19. 1:47processes you can see here you've got a subducting  oceanic plate and a continental plate that it is
20. 1:54subducting under you also have on the far left  mid-ocean ridge which we'll get to in other
21. 1:59episodes basically it's just where new crust is  forming because oceanic plate is spreading apart
22. 2:04and magmas coming up there forming new crust  this new crust is igneous because like we said
23. 2:10igneous rocks are what form from cooling magma  sedimentary rocks can form on the ocean basin
24. 2:16where sediment is accumulating and being  recompacted and lithified lithification is
25. 2:21just the combination of compaction and cementation  cementation is just necessary to stick the pieces
26. 2:28of sediment together into a new rock you can  also see that igneous rocks are forming from the
27. 2:33volcanoes that are erupting along the continental  edge of the subduction zone this heat and pressure
28. 2:39isn't only causing volcanic activity but it is  also causing deformation in the continental rocks
29. 2:45underneath the surface this is shown here by  these squiggly lines that are metamorphic rocks
30. 2:50and an important distinction to make here is  that metamorphic rocks only form when igneous
31. 2:56and sedimentary rocks or even previous metamorphic  rocks are put under extreme heat and pressure but
32. 3:02not extreme enough to melt the rock back into  magma completely because once a rock has become
33. 3:07magma again when it cools again it is now deemed  igneous this also emphasizes the way that the
34. 3:12cycle can jump around so metamorphic rocks can  be re-metamorphosed they can even be re-melted
35. 3:18and recoiled it to igneous rocks and seminar rocks  can become igneous again if they melt completely
36. 3:23or metamorphic if they're just subjected to high  pressure and heat and deform or metamorphic and
37. 3:28igneous rocks can be some sedimentary rocks from  erosion and re-lithification so it pretty much can
38. 3:34go any which way that you see it so now you can  definitely see why these look the way they look
39. 3:40you can see that the igneous rocks are crystalline  and the sedimentary rocks even like broken up
40. 3:45sediment that have been re-cemented together  like we discussed and you can see that the
41. 3:49metamorphic rocks look like they have all these  squiggly lines probably because they were forced
42. 3:54under extreme pressure forcing the minerals  to orient themselves in an elongate pattern
43. 4:00that to us looks like these squiggly lines are  what we call foliation thank you all for watching
44. 4:05and i hope you tune in next time to talk a little  bit more in detail about these types of rocks