1) order the following igneous rocks from slowest to fastest cooling rate (note

Question

1) order the following igneous rocks from slowest to fastest cooling rate (note some rocks may have similar cooling rates, put an equal sign between these when ordering them): 1: Rhyolite 2: Pumice 3: Gabbro 4: Granite 5: Ba 6: Obsidian 2) Now, using what you know about cooling rates, magma and lava, and using the figures provided in this lab as a reference, classify each of the above rocks as either plutonic (intrusive) or volcanic (extrusive) 3) Using what you've learned here and in class on in plate tectonics, volcanism and the melting the mantle lectures describe a geologic environment where each of the igneous rocks in question 1 might form/crystalize (choose from the following: a rift, subduction zone, mid-ocean ridge, pluton body, hot spot) Now find a location (state, region, etc using your computer/smartphone) in the United States where each of these environments is occurring or has occurred. For mid-ocean ridge environments you can look globally. 4)

Explanation / Answer

1. Fastest to Slowest Cooling rate: Basalt -> Rhyolite -> Obsidian -> Pumice -> Gabbro -> Granite

Rocks like Basalt and Rhyolite has almost same Cooling rate and are the fastest ones.

Rocks like Obsidian and Pumice has almost same Cooling rate and the the rapid ones.

Rocks like Gabbro and Granaite has almost same Cooling rate and are the slower ones.

2. When Magma cool and solidifies below the surface of the earth, the rocks which are formed are called plutonic rocks. Rocks with slow cooling rates are plutonic rocks. And Volcanic rocks are formed when the hot lava cools and solidifies on the earth's surface and thus the rocks with faster cooling rates are called volcanic rocks.

Basalt: Volcanic (Extrusive)

Rhyolite: Volcanic (Extrusive)

Obsidian: Volcanic (Extrusive)

Pumice: Volcanic (Extrusive)

Gabbro: Plutonic (Intrusive)

Granaite: Plutonic (Intrusive)

3. Rhyolite: Subduction Zone

Melting of Hot mantle fluxed by water and sediments that are carried into the mantle in subduction zones; and/or interaction of mantle derived basaltic magmas with the continental crust

Pumice: Rifts

Lumps of Pumice are formed during the volcanic activity in the rifts and rift valleys and are compressed into disc like forms in the rift zones.

Gabbro: Rift, Mid-ocean ridge

Found at divergent boundaries in rifts on lands and ridges in mid-ocean

Granite: Subduction Zone

Granitic rocks form deep within the crust and are associated with regions where two plates are moving towards each other in a zone of subduction

Basalt: Rift and Hot Spot

Formed by decompression melting of convectively uprising mantle at extensional plate boundaries, continental rifts and hot spots

Obsidian: Mid-ocean ridge

Obsidian-bearing volcanoes are typically located in or near areas of crustal instability or mountain building in mid-oceanic ridges

4. Mid- Oceanic Ridge- Gulf of California

Rift-   Rio Grande Rift (a series of rift valleys along faults in the Southwestern United States)

Subduction Zone- Cascadia subduction zone (it is a convergent plate boundary that stretches from northern Vancouver Island in Canada to Northern California in the United States)

Hot spot- Yellow Stone National Park (The North America Plate is slowly sliding across the surface of the earth and lying beneath this moving slab of crust is a volcanic hotspot, a vent fuming with heat)

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