The lines shown on the idealized graph illustrate the cooling histories for the
ID: 113289 • Letter: T
Question
The lines shown on the idealized graph illustrate the cooling histories for the three magmas listed below (the lines illustrate how magma temperature decreased with time). The cooling history for X
is best represented by ___, Y’s cooling history is best represented by ___, and Z is best represented by ___.
gabbro, basalt, obsidian
obsidian, basalt, gabbro
gabbro, obsidian, basalt
basalt, gabbro, obsidian
a)gabbro, basalt, obsidian
b)obsidian, basalt, gabbro
c)gabbro, obsidian, basalt
d)basalt, gabbro, obsidian
shorterlonger time low highExplanation / Answer
Solution.
The above graph shows a clear relation between the cooling history of magmas with time.
let us consider individually .
1. what is obsidian?
Obsidian is nothing but naturally occuring volcanic glass which forms due to sudden cooling of the magma i.e the temp of magma drops rapidly in a short span of time. This phenomena is clearly shown by the curve X in the above fig. Hence X is obsidian
2. What is Basalt ?
Basalt is a fine grained igneous rock which forms due to fast cooling of the magma when it reaches the earts surface. This phenomena is clearly shown by Y.
3. What is gabbro?
Gabbro is coarse to medium grained igneous rock which forms below the surface of the earth due to slow cooling of the magma. this is shown by the curve Z
hence the ans to the above question is option b.
obsidian, basalt, gabbro (ANS)
b)obsidian, basalt, gabbro (ANS)
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