Please reply to both POST1 and POST2 with at least 250 words

POST1:

Forthis week’s discussion post, I chose to write about limestone. Limestoneis considered an organic sedimentary type of rock, which is formedthrough the solidification of sediment. “Sediment is a naturallyoccurring material that is broken down by the processes of weatheringand erosion and is subsequently naturally transported” (Micu, 2019).These types of rocks also form by the overturning of the Earth’smaterial, such as the surface or bodies of water.

Limestone is composed primarily of calcium carbonate in the formof a mineral called calcite. This mineral can be one of three materials:organic, chemical, or detrital in origin. It forms in shallow, calm,warm marine waters where organisms are able to form calcium carbonateshells and skeletons. For example, when an animal dies, their shell orskeletal debris accumulate as a sediment that might be lithified intolimestone and form into this type of sediment. Most limestone can befound in areas between 30 degrees north latitude and 30 degrees southlatitude in areas like the Caribbean Sea, Gulf of Mexico, and around thePacific Ocean Islands. Limestone can also be formed as chemicalsedimentary rocks by direct precipitation of calcium carbonate frommarine or fresh water. Although these are thought to be less abundantthan biological limestone.

Limestone is known for its large amounts of marine animal fossilcontent that settled on the ocean floor over millions of years.Overtime, they were compacted, creating limestone from the sediments andpressure of the ocean floor. This tells us there was sitting water foryears and years where limestone is found today. An interesting factabout limestone in the area I live (San Antonino, Texas):

– San Antonio straddles the Balcones Fault.
– A limestone quarrywas built on the Balcones Fault, but has been reconstructed as theSunken Garden Theater which now holds concerts and plays.
– Since Ilive on limestone, I can only plant certain trees and plants since thelimestone is only a few inches below the dirt (we also have nobasements!).
– I live and work within a mile of our local quarry andevery Friday afternoon they blast the limestone to create crushed stone.My entire building shakes and is quite scary when you don’t know whatis going on!

Resources:
Limestone. (n.d.). Retrieved fromhttps://geology.com/rocks/limestone.shtml#:~:targe… ofLimestone, siderite, and other minerals.

Micu, A. (2019, April 24). The types of rock: igneous,metamorphic and sedimentary. Retrieved from https://www.zmescience.com/other/science-abc/types-of-rock/.

Nerc. (n.d.). How is limestone formed? Retrieved fromhttps://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/limestoneLandscapes/whatIsLimestone/howFormed.html.

POST2:

Therock of my choosing the Obsidian a natural igneous rock, volcanic glass,black in color with a smooth texture or what may appear to be shinywith a glassy, streak finish. Obsidian is absent from minerals due tothe crystalline process within the rock. The chemical process to formthis rock is formed through the geologic process of lava flow that isinitiated underground when the mantle pressure and heat intensifies, therock will melt to form magma that will rise up through the crust of thesurface and initiate the lava flow. Obsidian forms at the end of thevolcano cycle. The chemical composition includes about 70% of silicondioxide that is formed through rapid cooling from volcano lava. Changesin the magma water content can impact how streaks show up in the rock.The last Obsidian flow occurred over 1300 years ago at Newberry volcano.

Obsidian artifacts turn up at archaeological sites going back atleast as far as 1.7 million years ago, when an early member of the genusHomo made tools with it at the Ethiopian site of Melka Kunture. Tarkach(2019). Because the rock is hard and brittle Obsidian was useful in theStone Age for tools such as spears, scalpels for surgery and evenjewelry. Discovered by Native Americans it has made it’s way across thecountry Obsidian is found in Argentina, Canada, Chile Greece, Italy andUnited States in Oregon as a popular location to name a few.

Obsidian can also be found in reddish brownish colors as a result ofthe microscopic crystals and flow layers of the lava. A interesting factis obsidian it played a role in HBO’s hit Game of Thrones and while Inever knew this, it has made me want to go back and look at the series.

References

Andrei, Mihai. (2015) the types of rock, igneous, metamorphic an sedimentary, retrieved from https://www.zmescience.com/other/science-abc/types-of-rock/ (Links to an external site.)

TARLACH, GEMMA. Discover. Jun2019, Vol. 40 Issue 5, p26-30. 3p. 7 Color Photographs. , Database: Academic Search Premier (Links to an external site.)

Johnson, C., Affolter, M., Inkenbrandt, P., & Mosher, C., SaltLake Community College. (2017). An introduction to geology. Retrievedfrom http://opengeology.org/textbook/