Module #15 - Wave Action and Coastal Features
INSTRUCTIONS FOR TODAY
1. Watch the following Video of the Day: Japan Tsunami of March 2011 (42 minutes). Remember that most tsunami's are caused by major subduction earthquakes. This video highlights the events that led up to the major natural disaster that occurred on March 11, 2011. There will be a long answer question about this particular video on the Unit 3 test.
Be sure to make point form notes from this video in your digital video journal. Please make sure this document is SHARED with Mr. Durk.
3. Read the following information below in Part 1: Background and Terminology. Follow all hyper-links to external websites for activities, demonstrations and videos (if applicable). Copy only KEY information (i.e. the highlighted terms) to your digital notebook (in google docs) or paper notebook. Mr. Durk will be doing a notebook check today as part of your module evaluation. If you have been keeping notes on paper, please show these to Mr. Durk today. Take time today to get caught up on your virtual or paper notebook.
4. Complete Part 2: Blog Posting and post onto the Discussion Board (using the LMS)
4. Complete Part 3: Quiz #4: Glaciers and Glaciation. Complete between 11:15 - 11:45 am TODAY. This quiz is OPEN notebook and chromebook. This means you may use any and all resources available to you. You will only have 30 minutes to complete, and you can only do the quiz once. Good luck!
DUE DATE: Submit all components to Mr. Durk before Module #16 (Tuesday April 30th). Quiz must be completed today!
Part 1: Background and Terminology
Please remember to record all definitions and content in your virtual notebook. Definitions can be found by clicking on highlighted words.
The movement of energy through water causes waves. They usually result from distant winds or geologic effects and may travel thousands of miles before striking land. They range in size from small ripples to huge tsunamis. There is surprisingly little actual forward motion of individual water particles in a wave, despite the large amount of forward energy it may carry. Waves move water in circular motion as crests and troughs flow across the water’s surface. Energy moves through the water without actually carrying the water anywhere. It is largely ocean currents that cause water to flow from one place to another. There is surprisingly little actual forward motion of individual water particles in a wave, despite the large amount of forward energy it may carry. Waves can be broken down into two main types, deep water waves and shallow water waves.
As waves approach a shoreline, changes begin to occur when the water dept is approximately half of the wave length, as shown in the Deep Water vs. Shallow Water diagram above. The bottom of the wave is slowed by the frictional drag of the shallowing bottom, while the top of the wave continues on at its former pace. A breaking wave is one whose base can no longer support its top, causing it to collapse. Waves can also be classified as either constructive or destructive:
Constructive waves are usually associated with long fetch. They tend to be low in height (under 1 metre), have a long wavelength (up to 100 metres) and have a low frequency (around six-eight per minute). As they approach the beach, the wave front steepens only slowly, giving a gently spill on the beach surface. Swash rapidly loses volume and energy as water percolates through the beach material. This tends to give a weak backwash that has insufficient force to pull sediment off the beach or to impede swash from the next wave. As a consequence, material is slowly, but constantly, moved up the beach, leading to the formation of ridges (or berms).
Destructive waves tend to occur when the fetch is shorter. They are tall, toppling waves with a steep form and a high frequency (10–14 per minute). As they approach the beach, the waves quickly get steeper, and when breaking they plunge down and scour the beach. This creates a powerful backwash, as there is little forward movement of water. It also inhibits the swash from the next wave. Very little material is moved up the beach, leaving the backwash to pull material away. Destructive waves are commonly associated with steeper beach profiles. The force of each wave may project some shingle well towards the rear of the beach where it forms a large ridge known as the storm beach.
When destructive waves are common, coastal erosion takes place. This can be extremely sudden and expensive for landowners and resort areas.
As waves approach the shoreline on an angle (other than 90 degrees), it will cause the wave swash to move up the beach at an angle. The swash moves the sand up the beach at this angle, while thebackwash brings them, solely under the influence of gravity, directly down the beach. This has the net effect of gradual movement of the particles along the shore, known as longshore drift.
As review for the concepts of coastal erosion and to learn about the impact of wave height and landform material on the speed of erosion, complete the following simulation.