What extrusive igneous rock type cooled so quickly that visible crystal grains never grew, and the rock is composed entirely of black silicate glass that easily shatters into sharp, knife-like shards?

(A) Obsidian
(B) Pumice
(C) Scoria
(D) Tuff

Which of the following is evidence to the past existence of glaciers?

What is the difference between the cultures of central asia and the caucasus region? the majority of people in central asia are muslim; the majority in the caucasus region are christian. the primary language in central asia is armenian; the primary language in the caucasus region is russian. central asia has been plagued by ethnic unrest; the caucasus region has had little ethnic conflict. the effects of soviet rule can still be seen in central asia; the caucasus region has developed its own identity since the fall of the ussr.

Who believed that the universe was made of tiny uncuttable particles