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Chapter 3

Concept #1 Quiz

Concept #1 Quiz
Choose the best possible answer to the following questions about Key Concept 1 "The nature of magma and lava, and the effects of cooling and crystallization."

This activity contains 10 questions.

	Most magmas are dominantly molten rock (a liquid called “melt”). What are the other two, smaller percentage components of most magmas?   solid + gas crystal + lava solid + melt solid + crystal

	Which of the following describes best the difference between magma and lava?   a. Upon eruption, magma becomes “lava,” the form of the magma that flows out of the volcano. b. When magma gets to the top of the volcano it releases gas found within the magma, and the lava that escapes the volcano has therefore lost those gases. c. Lava is the name given to the ejected magma from a passive (fluid) volcano, but it is still called “magma” if it is erupted explosively, like at Mt. St. Helens. d. If the magma has no crystals or gases within it, it is called “lava.” Both a. and c. Both c. and d. All of these.

	Extrusive igneous rocks are _________, whereas intrusive igneous rocks are _________.   considered “plutonic” rocks because they form from lava extruded at the surface; considered “volcanic” rocks because they form from magma beneath the surface. considered “plutonic” rocks because they form from magma beneath the surface; considered “volcanic” because they form from lava erupted from a volcano. considered “volcanic” rocks because they form from magma beneath the surface; considered “plutonic” because they form from lava erupted from a volcano. considered “volcanic” rocks because they form from lava extruded at the surface; considered “plutonic” rocks because they form from magma beneath the surface.

	Which type of magma is most likely to quench into a natural glass?   highly viscous, cools quickly highly fluid, cools slowly highly viscous, cools slowly highly fluid, cools quickly

	Crystallization of magma occurs when ________.   the magma heats up and ions in crystals break their bonds due to expansion and Si and O ion vibration the magma stays the same temperature, causing ions to slow down and form crystals, mostly Si-O tetrahedra the magma cools causing ions to come closer together, the first ions being Si and O to form Si-O tetrahedra the magma comes in contact with water and freezes.

	Rocks that solidify from lava flows are typically finer grained than those that crystallize intrusively. Why?   Intrusive magma is cooler because it is well insulated by the surrounding rock. The extrusive magma, because it is deep below the surface, cools very slowly, producing very small mineral grains. The extrusive magma cools quickly so the mineral grains do not have time to grow any larger. Intrusive magma flows onto the Earth’s surface and cools very slowly, allowing many small mineral grains to grow.

	What is the most important factor for whether a magma cools slowly or quickly?   The presence or absence of volatiles (gases) – less gases = slower magma cooling. Pressure of the environment – lower P = slower magma cooling. The presence or absence of volatiles (gases) – more gases = slower magma cooling. Temperature of the environment – lower T = slower magma cooling. Temperature of the environment – higher T = slower magma cooling. Pressure of the environment – higher P = slower magma cooling.

	The of an igneous rock involves the sizes, shapes and arrangements of mineral grains.

	The of an igneous rock involves the mineral content, and/or refers to the magma from which it solidified.

	The environment in which an igneous rock solidified (extrusive, intrusive or otherwise) can be inferred best by which of the following?   the rock’s composition the rock’s texture the rock’s color the rock’s density

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