Pahoehoe and Aa can form in the same lava as it flows away from ...

[robinn137]

Pahoehoe and Aa can form in the same lava as it flows away from the eruptive vent. How does each form? What role does temperature play?
 
  What will be an ideal response?

Question 2

How does decompression melting generate magma at rift zones?
 
  What will be an ideal response?

[poopface]

Answer to Question 1

Answer: Pahoehoe produces smooth, ropy texture as the molten material on the interior of the lava flow continues to advance, stretching the cooling (but pliable) exterior of the flow. Aa is a rough, jagged texture produced as exterior cooling continues, but the warm interior lava still tries to flow.

Answer to Question 2

Answer: As the tectonic plates pull apart, pressure on the upper mantle will decrease while the temperature will remain constant. This change in pressure will allow some minerals to change phase from solid to liquid, a process that generates magma.

[robinn137]

Thanks for the timely response, appreciate it

[mcarey591]

TYSM