Exam 10: Volcanism and Extrusive Rocks

_________ crystallizes from an intermediate composition lava.

_____ refers to a rock's appearance with respect to the size,shape,and arrangement of its grains or other constituents.

________ are cavities in extrusive rocks resulting from gas bubbles in the lava.

Shield volcanoes have ___ bases and ___ inclined slopes.

Pahoehoe lava flow is characterized by a ropy or billowy surface.

Over 34,000 people died as a result of the ______ generated by the eruption of Krakatoa in 1883.

Silicic lavas,which are relatively high in silica,tend to be more fluid than mafic magmas.

Basalt is a variety of gabbro.

Several times in Earth's history,outpourings of magma covered many thousands of square kilometers in multiple flows called __.

Volcanic domes are steep-sided domes or spine-shaped masses of volcanic rock formed from viscous lava that solidifies in or immediately above a volcano's vent.

The islands of Hawaii are essentially a series of shield volcanoes built upward from the ocean floor over millions of years.

Condensation of the water vapor by degassing magma during the time following Earth's formation produced the ____.

The more _____ the lava,and the greater the amount of gas trying to escape,the more violent the eruption.

Individual layers of basalt lava may be divided into vertical columns called ______.

What are the three factors that influence viscosity of a lava?

Weathered volcanic ash and lava produce excellent fertile soils.

Tuff is a rock composed of fine-grained pyroclastic particles.

_____ describes the surface of a basalt flow with a smooth ropy surface.

_____ describes the surface of a basalt flow with a jagged,rubble surface.

The eruption of ______ is related to the fact that the North American plate is overriding a portion of the Pacific Ocean floor.