Author Question: Natural glass such as obsidian forms when ____. A)magma cools too rapidly for crystals to form ... (Read 203 times)

rlane42 · **on:** Jul 13, 2018

Natural glass such as obsidian forms when ____.
A)magma cools too rapidly for crystals to form
B)pegmatite melts, moves to Earth's surface and ,re-forms
C)magma cools too slowly for crystals to form
D)magma has a very low silica content
E)gas escapes through lava

Question 2

Stromatolites are the product of organic activity.
Indicate whether the statement is true or false