Igneous+Processes

**Honors Earth Science Igneous Processes Review** Define an igneous rock.-Rock formed by crystallization of molten magma-Phil L.

What is the difference between magma and lava?-magma is below the surface and lava is above the surface.-Phil L.

What is the relationship between crystal size and cooling rate? If the rock cooled quicker, the crystals would be small or not existent because it did not have time to form any. If the rock cooled slower, the crystals on the rock would be bigger, seeing that they had time to form. -Teri

Some igneous rocks don’t have crystals. They are called _. Which 3 rocks are they? Glassy textured rocks; pumice, scoria, and obsidian. -Teri

Compare plutonic vs. volcanic rocks (where are they formed?) // Volcanic rocks form when lava solidifies above the ground. Plutonic rocks crystallize under ground because they weren't able to reach the surface - Ron //

Compare intrusive vs. extrusive textures. Intrusive rock is rock that has crystallized from molten magma below the surface of the Earth.Extrusive rock is rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface The difference is the crystal sizes. Intrusive rocks have larger crystals, while extrusive rocks have littler to none crystals. -Teri

Compare felsic vs. mafic rocks (chemistry and color). Felsic rocks are lighter colored, contain more quartz and feldspar. High SiO2. Mafic rocks are darker colored, contain more iron minerals. High Fe, Mg. -Teri

How are volcanoes related to plate boundaries (2 ways)? When plates pull apart they can cause rifts like the Keweenaw rift. When plates push together they can cause big volcanoes and islands like Hawaii. -Molly Define and explain a hot spot. What and where are two hot spots in the U.S. ? In YellowStone and Hawaii - Ron
 * // Places on earth's surface that has experienced a long time of active volcanism - Ron //**

Contrast deep source vs. shallow source eruptions with regards to explosiveness, lava chemistry, temperature and viscosity. Shallow Eruptions: Thick, cooler, more explosive, and felsic. Thin lava tends to flow faster. Deep Eruptions: Thin, hotter, less explosive, and mafic. Thick lava tends to flow slower. -molly For each of the 4 types of volcanoes: give a geographic example, describe the physical shape and size of the volcano, its lava, its eruption behavior and any pyroclastics products it makes. Fissure eruptions: Keweenaw Peninsula, hottest lava, deep source depth, ocean and continent location, low explosiveness. -Teri Stratovolcanoes: Mt. Saint Helans, alternating/cooler lava, shallow source depth, continent location, high/alternating explosiveness. -Teri Shield: Largest volcano, Pahoehoe, very hot lava, deep source depth, ocean location, low explosiveness. -Teri Cinder cones: Smallest volcano, Sunset Crater, cooler lava, shallow source depth, ocean and continent location, small bursts of explosiveness. -Teri

What type of volcanism occurred in Michigan ? What happened to cause it? Where did it happen? It was a fissure erruption flood basalt volcano. Plates spreading apart caused this. It happened in the Keweenaw Rift ( Kewenaw Peninsula ) -molly

What are flood basalts? Flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thicknesses of hundreds of meters - Ron What does the texture of a porphyry indicate about its rate of cooling? that it cooled so fast that the atoms weren't able to arrange themselves. -molly What creates a vesicular texture? What 3 rocks might have it? Gas venting during formation; scoria, pumice, and basalt. -Teri

What are a few ways to identify a tuff? If the rock is extrusive and shows volcanic ash/rock fragments. -Teri

Compare and contrast aa and pahoehoe. Aa is sharp, jagged lava. Pahoehoe is smooth, rope like lava. -Teri

For each of these sizes, give an example of a common object that is the same size: Bomb = Size of a fist. Lapilli = Gravel size. Ash = Glass or sand size. Cinders = Usually gravel size. -Teri

How would you recognize obsidian? What type of chemistry does it have? Obsidian has a glassy texture, which shows conchoidal fracture. It's chemistry is always felsic. -Teri

What are the main gases given off during volcanic eruptions? Water vapor, carbon dioxide, and sulfur dioxide. -Teri

What is a pyroclastic flow? How is it different from an ash fall? Flows of superheated volcanic ash, debris, and gas. It is hotter then ash fall and can infuriate you at touch. –Teri // OK…I’m trying to picture this…but the word you really want is Incinerate! //

What are the top 3 dangers that can kill people during eruptions? Mud flows, pyroclastic flows, and poisonous gases. -Teri

How does a caldera form? Where are some calderas in the United States ? // A caldera forms when a volcano erupts and collapses within itself, you can find calderas in Yellow Stone and Crater Lake - Ron //