lab 4

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2232

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Geology

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Dec 6, 2023

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ES 2232G: Exploring the Planets & ASTRO 2232: Sun, Earth, Planets Laboratory 04 – Volcanism INTRODUCTION: The most common rock forming minerals are made up of elements that are abundant in the Earth’s crust and mantle. Minerals form in a specific order depending on the temperature at which they solidify. This is known as Bowen’s Reaction Series which is the progression of forming minerals when magma cools. Oxygen and Silicon are the most common elements in the earth’s crust and mantle, minerals made up with these elements are known as silicate minerals, they are the most common mineral group making up 90% of the earth’s crust. Bowen’s reaction series is made up of two separate branches the continuous and discontinuous. Minerals at the top of the branches crystalize first at high temperatures and as the magma cools the minerals further down the branches begin to crystalize. Rocks made up of the minerals which crystalize first are considered mafic (made up of minerals high in magnesium and iron) and rocks consisting of minerals from further down the chain are felsic (made up quartz and feldspars), a mixture of the two are considered intermediate in composition. Some examples are provided on the next page. For further background, see the Learning Module on OWL. Earth Sciences 2232G: Lab 04 1

Earth Sciences 2232G: Lab 04 2 DIORITE -A medium grained igneous rock which contains plagioclase, biotite and amphibole. GABBRO -A coarse grained igneous rock which contains olivine, pyroxene and plagioclase. GRANITE -A coarse grained igneous rock with quartz, plagioclase feldspars, biotite and muscovite.

Earth Sciences 2232G: Lab 04 3 PERIDODITE -A coarse grained igneous rock which contains olivine and pyroxene

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PART 1: CRYSTALLIZATION IN A MAGMA CHAMBER Question 1: If the above triangle is a magma chamber with crystallization occurring at various temperatures name, 2 minerals which are likely to form in each region: Region 1:__ Quartz and Muscovite________________ Region 2:___ Biotite and Amphibole______________ Region 3:___ Olivine and Pyroxene_______________ Question 2: What corresponding rocks are likely to form from each region and what composition will they have (i.e., mafic, felsic, or intermediate)? Region 1: Rock name: __ Granite_______ composition: _ Felsic____ Region 2: Rock name: __ Diorite______ composition: _ Intermediate_ Region 3: Rock name: __ Peridodite_______ composition: _ Mafic ____ PART 2: TYPES OF VOLCANOES Question 3: Identify the type of each of the following volcanoes Earth Sciences 2232G: Lab 04 4 800°C 1000°C 1100°C Region 1 Region 2 Region 3

A. Shield volcano__________________ B. Stratovolcanoes/Composite volcano C. Cinder/Scoria Cone______________ D. Stratovolcanoes/Composite volcano Question 4: Fill in the blanks concerning the following two figures: The volcano in the figure below is a Stratovolcano when lavas are high in silica with >60-70%, Explosive types of eruptions occur. These volcanos can also be produced by intermediate lavas which are l ow temperature and high in gas content. Earth Sciences 2232G: Lab 04 5 A B C D

The volcano in the figure below is a Shield Volcano it’s lava is low in silica and highly mafic , this result in a low viscosity lava, a gentle slope is a characteristic of these volcano types. PART 3: VOLCANIC FEATURES Earth Sciences 2232G: Lab 04 6

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When magma chambers extend up to the folding sedimentary rocks above, it will begin to cool and crystalize, this cooled mass is known as a batholith . There are multiple intrusive and extrusive features associated with a volcano. Some of these features were labelled on the previous two figures. Intrusive volcanic forms include batholiths, laccoliths, stocks, sills, dikes, pegmatite veins, and pipes. A stock is a prominent vertical extension on a batholith. Pegmatite veins are injected into the outer layers of a batholith and the surrounding rock when a batholith cools. Pipes are the result of magma escaping upward through sedimentary rock. When pipes reach the surface a volcano forms however if a pipe extends between layers of rock a sill will form. When a pipe spreads out to the degree that a sedimentary layer bends upwards from the pressure a laccolith forms. If instead of a horizontal spreading a vertical spreading occurs forming a dike. Radial dikes can occur close to pipes if vertical cracks occur due to the pressure of the magma moving up the pipe. Question 5: Label the volcanic features in the diagram below. A. Lateral Cone _________________________________________ B. Lava Flow ___________________________________________________________ C. Crater______________________________________________________________ D. Volcanic Neck with radiating dikes______________________________________________ E. Lahar flow_________________________________________________________ F. Radial Dikes ___________________________________________________________ G. Eroded laccoliths and ring dikes_________________________________________________ H. Laccoliths_______________________________________________________ Earth Sciences 2232G: Lab 04 7

I. Sill_________________________________________________________________ J. Volcanic Pipe Conduit_________________________________________________ K. Magma Chamber___________________________________________________ L. Batholith (unclear; if its pointing to the prominent vertical extension of the batholith, it is a stock) Earth Sciences 2232G: Lab 04 8

lab 4

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