370 - 345 Million Years Ago
Deposition occurs when land, be it soil or solid rock, is eroded by wind and water. |
370 million years ago, the place where you are standing at this moment was part of the continent of Euramerica. Most likely you would be standing in a few inches to a few feet of water and strange aquatic creatures would be swimming around your feet. This was the Devonian Period, characterized by shallow seas and abundant marine life. During the Devonian period, many of the sediments that make up the rocks in the buildings you are looking at were deposited at the bottom of these seas. Deposition occurs when land, be it soil or solid rock, is eroded by wind and water. Eventually, the sediment washed into the shallow seas that covered and surrounded the continent of Euramerica.
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Image From: http://thewatchers.adorraeli.com/data/uploads/2011/03/nutshell.gif
How the rocks were formed |
Compaction
The first step in this process is called compaction. Compaction occurs as layer upon layer of sediment build up. This creates pressure on the bottom layers of sediment. The pressure on the sediment squeezes the individual grains closer together. Cementation In between each grain there are little pockets of space. These spaces are called pores and are filled with water. Compaction decreases the space between grains, meaning that many grains touch. Cementation begins when minerals begin to precipitate out of the water in the pore space due to the pressure and heat that the sediments are exposed to. These minerals will then harden around each grain, effectively bonding it to the other grains around it. This process takes thousands to millions of years. |
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Sources for this page:
1. Acadian orogeny. (2016). In Encyclopaedia Britannica (Ed.), Encyclopaedia
britannica online. Retrieved from http://www.britannica.com/science/
Acadian-orogeny
Editors of Encyclopedia Britannica. (n.d.). Canadian shield. Retrieved November
4, 2015, from Encyclopedia Britannica Online website:
http://www.britannica.com/place/Canadian-Shield
2. Encyclopaedia Britannica (Ed.). (2016). Encyclopaedia Britannica Online.
Retrieved from http://www.britannica.com/place/Catskill-Delta
3. Geology for Dummies
1. Acadian orogeny. (2016). In Encyclopaedia Britannica (Ed.), Encyclopaedia
britannica online. Retrieved from http://www.britannica.com/science/
Acadian-orogeny
Editors of Encyclopedia Britannica. (n.d.). Canadian shield. Retrieved November
4, 2015, from Encyclopedia Britannica Online website:
http://www.britannica.com/place/Canadian-Shield
2. Encyclopaedia Britannica (Ed.). (2016). Encyclopaedia Britannica Online.
Retrieved from http://www.britannica.com/place/Catskill-Delta
3. Geology for Dummies