Looking Back on Lessons Learned…

This semester of Intro to Geology has been a very trying course. There’ve been many days where I’ve left class confused, disgruntled, or just downright frustrated with my not being able to grasp what processes are making our earth GO. Now that we’ve reached the end, however, I wanted to use this blog post to take the time to look back on all the information (both new and old) I’ve learned and recovered.

I now know the following facts about our Earth’s geologic makeup…

Igneous rocks are divided into three classes, depending on their silica content: felsic, intermediate, and mafic. Felsic rocks have a high silica content, low density, high viscosity, lower temperature, and tend to be continental. Intermediate denotes that they contain qualities in between felsic and mafic. Mafic rocks have a low silica content, high density, low viscosity, higher temperature, and tend to be oceanic. A felsic composition tends to lead to a more violent volcanic eruption while a mafic composition tends to lead to more quiet eruptions.

Moving right along with the topic of volcanoes, there are certain types that are very important. Scoria (Cinder Cone) volcanoes tend to be composed more of felsic material–specifically basalt–and tend to be mostly ash ejections. The Cascades and Andes mountain ranges are good examples of this volcanic type. Shield volcanoes are the largest volcanoes, spanning great distances across a landscape. They too are composed mostly of felsic material, and eject tephra–mostly lava–from the center. The chain islands in Hawaii such as Kilaeau and Mauna Loa are good examples of shield volcanoes. Composite volcanoes tend to consist of an intermediate mixture of rock–mostly andesite–and can be some of your most violent eruptions. The deadliest part of a composite volcano is the pyroclastic flow that hugs the earth as it travels at whopping speeds down the sides of the volcano. Five great examples of this volcanic type include Mt. St. Helens, Vesuvius, Mt. Fuji, Mt. Kilimanjaro, and Mt. Etna. The last type of volcanoes is calderas, which are basically craters/remnants of ancient supervolcanoes that carved a basin out of a landscape. Calderas form in four basic steps: venting, bulging, erupting, and then the crater that is left gets filled in. Yellowstone, Santorini, and Crater Lake are fantastic examples.

When it comes to types of rocks, there are three: igneous, sedimentary, and metamorphic. In the igneous category, there is rhyolite (felsic), granite (felsic), diorite (intermediate), andesite (intermediate), basalt (mafic), gabbro (mafic), and obsidian. In the sedimentary category, there is sandstone (clastic), siltstone (clastic), shale (clastic), breccia (clastic), conglomerate (clastic), graywacke (clastic), coal (nonclastic), limestone (nonclastic), and gypsum (nonclastic). Lastly, in the metamorphic class, there is hornfel (contact), skarn (contact), marble (contact/regional), gneiss (regional), slate (contact), quartzite, phyllite, amphibolite, serpintinite, schist, greenstone, and green/blueschist.

The last thing I really want to talk about is that of the six principles used to determine the relative ages of rocks. First, there is the Principle of Superposition–says that older rock is situated/layered underneath younger rock. Second, there’s the Principle of Horizontality–rock layers are arranged horizontally. Third, there’s the Principle of Inclusion–layers of younger rock can contain pieces/remnants of older rock. Fourth, there’s the Principle of Lateral Continuity–rock layers cut straight across a landscape in bands. Fifth, there’s the Principle of Cross-Cutting Relationships–younger layers of rock can cross-cut layers of older rock, but are still younger in age. Lastly, there’s the Principle of Faunal Succession–where fossils are used to help determine the surrounding rock’s relative age.

Although there’s a lot more I could say, Intro to Geology has been an enlightening, fascinating class that I’ve enjoyed. Thanks to Dr. Pillar for a great semester—I’ll miss ya in the spring!


About willdogg10

I am a renegade in this world, challenging both myself and others to become more and more inspired by our faith and the God for whom we live every single day. May we take heart in the possibilities that LOVE and SELFLESSNESS have to offer us, and may we come to realize that the greatest luxuries in life are those we participate in that belong to Someone greater.
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3 Responses to Looking Back on Lessons Learned…

  1. Yin Thu Htin says:

    Wow!!!!!!!! Thanks so much for posting this kind of revision as blog!!!!!!!! It is really amazing and I can revise something by reading this blog!!!!!!!!!! Thanks a lot.

  2. danbailey11 says:

    Thanks for this post. Trust me you wasn’t the only one leaving class feeling that way lol. This post contains a lot of useful information that I can use to study. Thanks again

  3. kevinhornik says:

    Great post. I never thought of doing this in a blog post but I definitely do agree that we’ve learned a lot this year. I thought this was going to be the same stuff I learned in high school earth science, and in some areas it was. But i learned so much, and even in the areas i had already studied, i learned so much more.

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