Debate which energy sources effectively balance human needs with ...

[Jramos095]

Debate which energy sources effectively balance human needs with environmental concerns.
 
  What will be an ideal response?

Question 2

Consider a sample of porphyritic andesite, which is common in Pacific Rim volcanoes. Speculate how this sample may have formed (simply defining porphyritic isn't enough, be specific).
 
  What will be an ideal response?

[mammy1697]

Answer to Question 1

Answers might mention coal, nuclear, solar, hydro, natural gas.

Answer to Question 2

Answer: The formation of porphyritic igneous rocks typically involves a two-stage cooling process. Deep inside the volcano the minerals that form andesite begin to crystallize. As the volcano erupts, the liquid portion of the lava cools rapidly, inhibiting mineral growth and thus creating two crystal sizes within the groundmass. Hornblende is a typical phenocryst for andesite.