111-20 - GY 111 Lecture Notes D. Haywick (2008-09) 1 GY 111...

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GY 111 Lecture Notes D. Haywick (2008-09) 1 GY 111 Lecture Notes Sedimentary Environments 3: Beaches Lecture Goals : A) Types of modern beaches B) Wave and beach dynamics C) Beach sedimentation Reference: Press et al., 2004, Chapter 7, 17; Grotzinger et al., 2007, Chapter 20, p 485-491 GY 111 Lab manual Chapter 3 A) Types of modern beaches I've lived in Mobile for about 17 years. During that time, I've complained about the weather (too hot, too wet, too many damn hurricanes), Mobile drivers, Airport Blvd, the weather again, and our crappy local news media. The one thing I have never complained about are the local sedimentary environments. In particular, our beaches are the envy of the world (really! geologists come here to study beach dynamics). It is true that some of our beaches are in trouble (more about this shortly), but we can still learn an awful lot a beach sedimentation in our area. First of all, it is important to note that there are lots of types of beaches. Most are sandy in that sand is deposited on them, but some are sites of gravel deposition. These gravel beaches are usually called shingle beaches and they are common along rocky coastlines and/or coastlines that are in cooler temperate areas (e.g., New Zealand, Canada). The reason is that colder areas have less intense chemical weathering resulting in larger sedimentary particles. Beach gravel tends to be very well rounded and discoidal in shape which makes excellent skipping stones.
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GY 111 Lecture Notes D. Haywick (2008-09) 2 Sand beaches are more typical for our part of the world. They can be attached to the mainland ( mainland attached beaches; see picture on the previous page of a beach in New South Wales, Australia)) or detached ( barrier islands; see picture to left on this page). The side of the beach that is in direct contact with ocean waves is called the open side because it is open to the full force of the wind and waves. On barrier islands, the side of the beach that in on the lagoonal side is called the sheltered beach because it is sheltered from the most powerful waves. Most people regard the beach as the part of the shoreline where you sit down to get a tan. Geologists actually have a more inclusive definition of the beach. It is the sedimentary environment that extends from the sand dunes landward of the high tide line to the point offshore where water depth reaches 10 m. Seaward from here is the continental shelf. The actual width of the beach depositional environment is highly variable. In southern
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This note was uploaded on 02/04/2012 for the course GLY 111 taught by Professor Haywick during the Fall '11 term at S. Alabama.

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111-20 - GY 111 Lecture Notes D. Haywick (2008-09) 1 GY 111...

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