Graded Homework

1. Recall from your reading about the nature of volcanoes to choose the best answer: Magma tends to rise toward Earth’s surface principally because __________.
   

   		of magma cooling
   		mounting pressure within the reservoir
   		rocks become more dense when they melt
   		of convection in the mantle

2 points

Question 2

1. Recall from your reading about the principle types of volcanoes to choose the best answer: Crater Lake, a caldera, formed from the collapse of a __________.
   

   		composite volcano.
   		shield volcano.
   		cinder volcano.
   		lava dome

2 points

Question 3

1. Recall from your reading about the nature of volcanoes to choose the best answer: Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface?
   

   		Aa
   		Pahoehoe
   		Pumice
   		Scoria

2 points

Question 4

1. Which of the following is NOT the property of radioactive decay?

   		During Alpha emission an atom’s proton number is decreased by 2.
   		During Beta emission an atom’s proton number is increased by 1.
   		During Alpha emission an atom’s neutron number is decreased by 2.
   		During Beta emission an atom’s neutron number is increased by 1.

2 points

Question 5

1. Recall from your reading about the nature of volcanoes to choose the best answer: A volcanic eruption is driven by __________ and __________ which forces its way upward and may ultimately break though zones of weaknesses in the Earth’s crust.
   

   		heat; water pressure
   		heat; gas pressure
   		buoyancy; gas pressure
   		buoyancy; water pressure

2 points

Question 6

1. Recall your reading of Relative Time Scale and Radiometric Time Scale and match the term with the definition.

	Isotopes

	Half-life

	Carbon 14

	Igneous rocks

	Hutton

	Petrology

	Index fossil

1. Stratigraphy

   A. Isotope found in all living plants and animals B. Forms of life which existed during limited periods of geologic time and thus are used as guides to the age of the rocks in which they are preserved C. Studies on the origins of the various kinds of rocks D. Atoms of the same element with differing atomic weights E. Rocks that generally do not contain fossils F. The Scottish geologist who first proposed the fundamental principle used to classify rocks according to their relative ages G. Studies of rock layering H. The time it takes for one-half of a particular radioactive isotope in a sample to decay

8 points

Question 7

1. Recall from your reading of Principal Types of Volcanoes, and match the description to the type of volcano.

	Large, fairly steep-sided cones composed of alternating layers of lava flows and pyroclastic material.

	Small basaltic cones built during one, short, eruptive episode; dominated by cinders.

	Volcanoes of southwestern Alaska and the Aleutian Islands.

	Big volcanoes of Hawaii

	Volcano Paricutin in Mexico

	Forms dikes from lava

	Lava is produced after the eruption and flows from the bottom

1. Volcanoes with gentle slopes spreading over large areas

   A. Cinder cones B. Composite/stratovolcanoes C. Shield volcanoes

8 points

Question 8

1. Recall from your reading about the radiometric time scale to put the following isotopes in order of use, from oldest rock to youngest.

Carbon-14

Potassium-40

Samarium-147

Thorium-232

Uranium-235

Uranium-238

1. Rubidium-87

7 points

Question 9

1. In your own words, briefly explain how a caldera forms from principle types of volcanos.

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10 points

Question 10

1. Recall from reading the nature of volcanoes, and in your own words, briefly discuss how the rate of cooling determines the type of rock that forms from magma/lava.

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10 points

Question 11

1. According to the figure below, give an approximate age for the Dakota Sandstone and for the Wasatch Formation. Explain what evidence you used to determine this.

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10 points

Question 12

1. In your own words, compare and contrast relative age dating with radiometric dating. What are the strengths and limitations (if any) of each? Reference USGS (2001).

   Your response should be at least 200 words in length.

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37 points

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