Online Homework System Assignment Worksheet 6/3/04 - 1:20 PM

Name: ____________________________ Class: geol100 Class #: ____________________________ Section #: ____________________________ Instructor: Darryll T. Pederson Assignment: waves and beaches This unit is designed to be a review for the topic of waves and beaches and eventually an exam. As such, there is considerable discussion about the processes and factors that impact on a given beach setting. The use of photos and diagrams is important as most students do not get a visual image to analyze when trying to put a number of concepts together to answer a question. The questions are designed to be learning questions in that many processes and factors are presented in a fact type setting in the initial part of the question text. The scoring of each question will provide immediate feedback to the student to correct any misconceptions and strengthen the base for answering later questions. The student will receive 10 points toward total points for the class. Answers will be highlighted in red

Question 1: (1 point) Wave energy is a function of which of the following options? Click all that apply. (a) Fetch (b) Direction (c) Wind speed (d) Duration (e) Sunshine

There are 3 key factors that determine wave energy- Fetch, Wind speed, and Duration. This type of question represents knowing all three for total credit. The factors will be important in addressing later questions in the text so after the student finishes this question

Question 2: (1 point) The greater the wavelength, the faster the waveform travels. (a) True (b) False

Question 2: (1 point) The greater the wavelength, the faster the waveform travels. (a) True (b) False

This question is strictly a knowledge question, but the concept will be used later in the review and is asked here to set the student on track if needed.

Question 3: (1 point) Tsunamis have very long wavelengths. Select all characteristics that apply. (a) Velocities greater than normal waves (b) Form breakers in open ocean (c) Not detected in open ocean (d) Have shallow wave base (e) Amplitude is much less than wavelength

Knowledge question. Student is asked to provide unique characteristics of tsunamis waveform.

Question 4: (1 point) A trough forms at the leading edge of a water waveform. This explains why the arrival of a tsunami wave is signaled by a withdrawal of water from the shoreline (a) True (b) False

Question 4: (1 point) A trough forms at the leading edge of a water waveform. This explains why the arrival of a tsunami wave is signaled by a withdrawal of water from the shoreline (a) True (b) False

Application type question. Student is asked to translate a fact into a reality.

Question 5: (1 point) Tsunami’s can be caused by which of the following? (a) Earthquakes (b) Meteorite impacts (c) Volcanic explosion (d) Strong winds (e) Landslides

Knowledge question-main processes that create tsunamis .

Question 6: (1 point) As waves approach the shore, a point is reached where the wave form starts dragging on the bottom as the ocean depth decreases. The overall result is the wave form slows down, steepens, and wavelength decreases. Because of the drag of the bottom, there is a net shoreward transport of water. This drag starts occurring when D is what fraction of A?

(a) 1/2 (b) 1/3 (c) 1/8 (d) 1/1 (e) 1/4

Application type question-First re-enforces fact, than requires translation to graphical sketch.

Question 7: (1 point) Because of the interference of the bottom with the wave form, the forward velocity of the wave decreases. Except for the energy lost because of friction with the bottom, the energy of motion is translated into increasing wave height. Eventually so much energy is stored in the wave height that the wave form breaks. Choose all choices that apply.

(a) More waves hit the beach in a given period of time (b) Fewer waves hit the beach in a given period of time (c) The wavelength decreases as the waveform approaches the beach (d) Length C on the figure should be less that length A

(e) If one knows the wavelength of the open water wave, observation of where the wave steepens can be used to determine the depth of water at that point

Question requires translation of particle motion in waves feeling the bottom to geometric effects.

Question 8: (1 point) A given water particle in a wave form moves in an elliptical path in a plane perpendicular to the wave front. The size of the ellipse for water particle movement decreases with depth until at a depth of 1/2 wavelength, effective motion decreases. If you are floating in the water, the crest of the wave form as it approaches would move you toward the beach and lift you to the crest of the wave. As the wave crest passes, you would start moving away from the beach and downward into the approaching trough. The swimmer in the picture would have what type of movement in the upcoming seconds?

(a) Toward shore (b) Away from shore (c) Upward (d) Downward

Using a photo in this question allows translation to-yes even people follow the laws of physics .

Question 9: (1 point) The beaches on the northern shore of the Island of Ohau have some of the mos t extreme surfing in the world. A world record was set in the Spring of 2004 with a sucessful surfing of a 72 foot wave. These giant waves are formed for the following reasons -click all that apply.

(a) Prevailing Westerlies affecting area to west in winter (b) rapid shallowing of water depth (c) Beach sediment is fine grained (d) Pacific Ocean offers long fetch for wave development (e) short wavelengths travel faster than long wavelength waves

One again, adds a human dimension to a basic question about wave formation.

Question 10: (1 point) The wave in the photo is breaking right at the shoreline. There is no steeping of the waveform further out from the beach. This suggests --click on all that apply.

(a) Beach face is hard (b) Ocean bottom is shallowing slowly (c) Ocean bottom is shallowing rapidly

(d) One cannot "touch" bottom a short distance from the shoreline (e) Beach sediment absorbs the wave energy

One of the features of EDU is showing the effect of physical processes and be able to ask for ramifications.

Question 11: (1 point) In this photo, the incoming waves are breaking far from shore. Select all from the choices below that describe the setting.

(a) Small waves still reach the beach (b) Big waves still come through every few minutes. (c) The fine-sand particles break up the waves (d) The bottom is fairly shallow out to the breaking waves (e) The waveform is retrograde after breaking

This is a complicated question- many aspects of wave interaction with the beach need to be considered. Photos help.

Question 12: (1 point) What is the source of water running back to the ocean shown on these two photos?

(a) Backwash from the previous wave running up on the beach (b) Stream flow (c) Groundwater discharge (d) The water is not running down the beach (e) The tide is going out

Use of photos allows students to study actual processes in addition to applying conceptual processes.

Question 13: (1 point) The on-rushing wave sweeps moves sand and debris up the beach face. The maximum point that any given wave reaches is recorded by a line of debris known as a swash mark as shown in the photo.

(a) True (b) False

Once again, the use of a photo allows student to actually identify a swash mark.

Question 14: (1 point) Fill in the blanks: As waves approach a beach, the wavelength ____________ the amplitude ____________ and the waveform ____ down.

Question 14: (1 point) Fill in the blanks: As waves approach a beach, the wavelength ____________ the amplitude ____________ and the waveform ____ down.

This is a fill in the blank question with several choices provided including –increases, increases, slows

Question 15: (1 point) Fill in the blanks: The waves in the photo are breaking because the wavelength is more than twice the depth of the water. The period or frequency of the wave is the same even though the wavelength is decreasing as the waveform approaches shore.

Question 16: (1 point) As waves approach a beach at an angle, the part of the waveform closest to the beach starts dragging first. This causes a bending of the waveform so it approaches the beach at a decreasing angle. This is called refraction as water waves are bent the same way as light rays. This process causes the following consequences. (a) longshore drift is in the original direction of wave approach (b) Energy of waves is focused on bays (c) Wave energy is focused on headlands (d) Waves usually move sediment at a small angle up the beach (e) Backwash of sediment is straight down the beach face

The photo in the previous question provides some keys to what geometries are present in this question. Remember??

Question 17: (1 point) Beaches sometimes have a series of same-sized arcs in the beach face. They often appear after major storms and maintain the geometric form for long periods of time. In the photo are a series of these forms extending in sequence along the beach face. Click all choices that describe the features in the photo.

(a) Backwash focused in the indentations . (b) Rip currents sometimes develop at the center of larger beach cusps (c) Beach cusps (d) Form only during extended good weather (e) Groundwater discharge in the indentations .

In geology interpretation of observations is all important. This photo makes it more than a book type question.

Question 18: (1 point) The problem is to generate an equation that will calculate when the depth when a waveform of a given wavelength starts

dragging the bottom. Present your answer in terms of a mathematical equation with depth = (some relationship to wavelength)

This question requires constructing a simple mathematic equation. Depth= ½ wavelength.

Question 19: (1 point) Sediment making up beaches reflects the source of the sediment. Local rivers discharging along the coastline are a common source of beach sediment. The sediment provided by these rivers reflects the geologic deposits in the river basin. Reefs, where present, also represent a potential source of beach sediment when they are broken up by wave action. This sediment is commonly a carbonate mineral of some type. The beach shown in the photo is on the margin of a volcanic island composed of basaltic composition rocks and sediments. What is the likely source of the beach sediment. Click all that apply.

(a) Reefs

(b) Ash fall deposits (c) Coral (d) Weathered lava flows (e) Discharging rivers

This complex question requires geologic understanding of mineralogy and environment of formation.

Question 20: (1 point) On the Big Island of Hawaii, there are black-sand beaches and more rare, green-sand beaches in addition to white/tan- sand beaches which reflect broken reefs and corals. Olivine is a green mineral which forms at high temperature from a basaltic composition magma. The rock cliffs shown in the photo are of basaltic composition. If the beach in the photo were black or green in color, the source of sediment on the beach would be from what source? Click all that apply.

(a) Corals (b) Weathering of island rocks (c) Rivers draining island

(d) Longshore transport from where rivers drain into the ocean (e) Reefs

A number of geologic concepts and processes are required. The photo allows additional considerations.

Question 21: (1 point) The beach across the valley in the photo is formed on deposits that have filled a much deeper valley that was cut when ocean water levels were much lower during glacial periods. What is the source of sediment forming the beach? click all that apply.

(a) Reefs (b) Weathered volcanic rock (c) Sediment shed from slopes of valley (d) The river in the photo (e) Coral

The photo allows the intertwining of a number of geologic considerations .

Question 22: (1 point) Why are the waves approaching nearly parallel to the beach and to the adjacent headlands. Click all that apply.

(a) Waves are coming from different sources (b) Water is shallower than 1/2 wavelength (c) refraction of original ocean waves (d) Short period waves not present (e) Interference with the bottom by the waveform

The photo permits the inclusion of a number of geologic considerations and visualization.

Question 23: (1 point)

What is the depth of water, in meters, where the waves first start breaking if the wavelength is 40 meters? (a) 20 (b) 80 (c) 10 (d) 160

The wavelength is picked by a random process; the student selects the correct choice.

Question 24: (1 point) Longshore drift is cause by the wave washing up on the shore at an angle and with the backwash flowing straight down the beach face. The result is a continuous series of movement of the sediment at an angle up the beach face and return of the sediment down the face at some distance down the shoreline. In the photo, what direction is the sediment being transported?

(a) From upper right to lower left (b) Onshore (c) From lower left to upper right (d) From upper left to lower right (e) From lower right to upper left

This question requires interpreting geometric relationships as well as geologic processes .

Question 25: (1 point) Longshore transport results in movement of sediment along the beach face. The direction of transport depends on the direction of approach of waves. It is common for Winter storms to generate waves approaching the beach at a different direction as compared to Summer storms. Some beaches on the Big Island of Hawaii and on the coast of California are present in the Winter, but absent in the Summer. Check all possible causes for these changes.

(a) Prevailing westerlies predominate in the Winter (b) Winter storms coming off the Pacific Ocean in the Winter have more energy (c) Longshore transport moved the sand on down the beach in the Winter (d) Fewer tourists mean's less erosion (e) Surfers caused more erosion in the Winter

In part this is a reality question-can translate wave effect to people effect. Waves much more predominate.

Question 26: (1 point) Longshore transport of sediment can lead to the development of the following features. Check all that apply. (a) Spits (b) Baymouth bars (c) Delta's (d) Offshore bars (e) Hooks

Strictly a knowledge question. Vocabulary and concepts are the main thrust.

Question 27: (1 point) If a barrier such as a groin is constructed perpendicular to a beach face the beach sediment will accumulate on which side of the barriers? Check all that apply.

(a) On the opposite side of the direction of longshore drift (b) The sediment will accumulate in equal amounts on each side of the barrier (c) There will be no effect (d) On the side where waves are approaching the beach (e) On the downstream side representing the direction of longshore drift

The photo re-enforces the concept of a groin.

Question 28: (1 point) Transport of sediment in all geologic environments is a function of the energy available for transport. Larger particle sizes can only be transported in higher energy environments such as more rapidly flowing streams or by larger waves approaching a beach. High energy waves impacting on a beach would likely result in the beach having what of the following characteristics? (a) Steeper beach faces (b) Smaller particle sizes

(c) Gentle slopes on the beach face (d) Large particle sizes (e) Cobble-sized particles as compared to sand-sized particles

Question requires integration of geologic concepts and reality considerations.

Question 29: (1 point) Hurricanes generate very high energy waves. In addition, the low atmospheric pressures associated with hurricanes and the directional push of the wind can cause much higher water levels along beaches. All factors combine to cause large trans fers of beach sediment. Check results that might be expected during a hurricane. (a) Deposition of fine sediment such as clays and silts on beach face (b) Rapid landward erosion of the beach face (c) Transport of sand-sized sediment to deeper water (d) Breeching of dune barriers (e) Breaking of waves closer to shore as water depth greater

Question requires integration of a number of geologic processes and real world processes -with facts presented.

Question 30: (1 point) In 1992, a very strong hurricane struck the Island of Kauai. The hurricane completely engulfed the island topping all power and telephone poles as well as destroying many man made structures on the beaches and throughout the island. Some of the most popular beaches on the island were nothing but bare volcanic rock after the hurricane. Where did the carbonate sand that comprised the beautiful beaches go? Check all possibilities. (a) Washed inland (b) Carried to deeper offshore areas (c) Residents used it to rebuild their homes (d) The carbonate sediment was ground to clay particles (e) Blown away by the wind

Question 30: (1 point) In 1992, a very strong hurricane struck the Island of Kauai. The hurricane completely engulfed the island topping all power and telephone poles as well as destroying many man made structures on the beaches and throughout the island. Some of the most popular beaches on the island were nothing but bare volcanic rock after the hurricane. Where did the carbonate sand that comprised the beautiful beaches go? Check all possibilities. (a) Washed inland (b) Carried to deeper offshore areas (c) Residents used it to rebuild their homes (d) The carbonate sediment was ground to clay particles (e) Blown away by the wind

This question requires understanding of mineralogy and wave action.-clay minerals are not formed from carbonates.