SECTION III.. Define the Crust of the Earth. Rocks.

Define the crust of the earth. Rocks.

What are the unstratified rocks?

What is the structure of granite?

How are the varieties distinguished?

What is the porphyritic structure?

Describe hypersthene rock.

What are volcanic rocks? Lava? Scoriæ? Pumice-stone?

How is the vesicular structure produced?

What are volcanic breccias? Volcanic grits?

What is the composition of the trappean rocks?

What is the amygdaloidal structure?

What are the three varieties of trappean rocks, and how are they distinguished?

Name the stratified rocks. Describe gneiss. Mica slate. Sandstone. Conglomerate. Greensand. Describe the varieties of limestone.

What is dolomite? Of what does clay consist? Clay slate? What modifications does clay slate present? What is diluvium?