GEOL101 - Slideshow 101.10 Magma

GEOL101 - Slideshow 101.10 Magma - Magma Magma Melting...

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Magma Magma   Me lting   C rys ta lliza tio n  Pro c e s s e s  tha t im pa c t c o m po s itio n
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Magma Creation of Magma Unlike  s no w, ro c k do e s n’t a ll m e lt  a t o nc e , b e c a us e  ro c ks  a re   m a de  up o f s e ve ra l m ine ra ls ,  e a c h with its  o wn m e lting  po int. This  re fle c ts  the  s tre ng th o f its   b o nds . Partial Melting : a s  ro c k is   he a te d, no t a ll m ine ra ls  m e lt a t  o nc e . S o m e  m ine ra ls  m e lt b ut s o m e   (with hig he r m e lting  po ints )  re m a in s o lid (e .g ., c a ndy b a r) Partially melt peridotite basalt magma Partially melt basalt andesite magma Partially melt andesite rhyolite magma
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Magma Factors that control melting:    Heat   Pressure   Water Content Factors controlling melting Factors controlling melting
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Magma The  fo ur pla c e s  o n Ea rth whe re  m a g m a  fo rm s : Hot Spot Subduction Zone Mid Ocean Ridge Continental Rift
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Magma Magma Heat Temperature of the Earth increases with depth . Geothermal Gradient So… rocks at depth will melt. ________________________ The top of Asthenosphere is ~1% liquid  (partially melted).  So… Lithospheric plates “float” on it. Factors controlling melting Factors controlling melting G e o the rm a l G ra die nt
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Magma Pressure : Increased heat melts rock because vigorous thermal vibration breaks the mineral lattice apart.  But high pressure counters this effect by squeezing the atoms together - holding the ions and  atoms in a crystalline solid closer together. At higher pressures it harder to vibrate and break bonds. So. ..with increase pressure (i.e. deep down in the Earth) the temperature needed to melt the  rocks also goes up. Factors controlling melting
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GEOL101 - Slideshow 101.10 Magma - Magma Magma Melting...

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