1) How would you tell if a rock is crystalline? a. It contains crystals that hav
ID: 109184 • Letter: 1
Question
1) How would you tell if a rock is crystalline?
a.
It contains crystals that have been cemented together.
b.
It does not contain crystals at all.
c.
It contains interlocking crystals.---------
d.
It contains all one type of crystal.
2) Which of the following is NOT an effect volcanic eruptions can have on climate?
a.
They can dim the stars.
b.
They can lower temperatures for at least a season.
c.
They can increase the growth rate of tree rings.
d.
They can cause more radiant sunsets.
a.
It contains crystals that have been cemented together.
b.
It does not contain crystals at all.
c.
It contains interlocking crystals.---------
d.
It contains all one type of crystal.
Explanation / Answer
Answer 1 c: A rock is crystalline if it consists of entirely interlocking crystals without any glassy matter. Plutonic rocks which are igneous rocks and formed slowly and at depth are always crystalline rocks whereas extrusive igneous rocks or volcanic glass which are formed quickly on eruption of lava do not have time to form crystals and are generally partly of entirely glassy. Metamorphic rocks are also always crystalline. The clastic sedimentary rocks are not crystalline in which the grains are bound together by cement. But the sedimenatary rock like crystalline limestone which are formed by the precipitation directly from the solution.
Answer 2. c. During the volcanic eruption it adds sulphur dioxide, particles of dust and ash and greenhouse gases like carbon dioxide and water vapour into the atmosphere. These particles can cover the sky and reduces the amount of sunlight reaching the earth. This in turn results in cooling and reduces the global average temperature. This can reduce the period of summer season. Due to the presence of aerosols and dust particle, the light of the stars can dim in the sky and they are not easily visible from the earth. During the volcanic eruption due to cooling the growth of tree is effected. Very sensitive trees respond by not growing at all during this period. Also a short growing season means no growth of tree ring at all.
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