why do intrusive and extrusive igneous rocks have different sized crystals? [a-intrusive/extrusive rocks cool at different rates,leading to different sized crystals OR [b-intrusive/extrusive rocks cool at the same time,but have different solidifying temperatures OR [c-intrusive rocks are formed in the northern hemisphere and extrusive in the southern hemisphere causing the different sized crystals or [d-intrusive and extrusive rocks have the same sized crystals?
2006-06-22 07:41:03 · 4 answers · asked by Anonymous in Education & Reference ➔ Homework Help
I'm quite sure it's A, extrusive rocks are exposed and cool very quickly. Since they cool rapidly, crystals have no time to grow, and most crystals are smaller than a millimeter. Obsidian, in fact, has no crystals at all and is a type of glass. Intrusive rocks (such as granite) on the other hand, cool slowly (as they are insulated by the earth) and larger crystals form.
For further information,
http://www.geology.ufl.edu/Class_Notes/GLY2010_Fall_1996/summaries/intrus1.html
http://www.nps.gov/brca/Geodetect/Rocks%20&%20Minerals/igneous.htm
Hope this is helpful.
2006-06-22 08:17:12 · answer #1 · answered by purplekitten 5 · 0⤊ 0⤋
Recalling from my geology class, I believe the correct answer is A. I checked it out at: http://www.wsu.edu/~geology101/sec3/Chapter%205.html
2006-06-22 14:57:08 · answer #2 · answered by Tom D 2 · 0⤊ 0⤋
A absolutely
2006-06-23 09:57:02 · answer #3 · answered by kitty 3 · 0⤊ 0⤋
Answer is B (I'm just guessing, it sounds good).
2006-06-22 14:45:16 · answer #4 · answered by mageta8 6 · 0⤊ 0⤋