Ch.15 Geology 1401 – Flashcards
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How does water move as waves pass?
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Water moves in a circle in the same direction as wave movement.
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How does wave amplitude change with depth in water?
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Wave amplitude decreases as depth increases.
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What is the wave base?
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the lower limit of wave-induced motion in the water
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What is the relationship between wave base and wavelength?
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The depth of the wave base is one-half the wavelength of the waves.
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Why does wave height increase as waves enter shallow water?
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The energy of the wave must be contained within a smaller water column in shallow water.
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Why do ocean waves bend around headlands?
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The waves are moving more slowly just in front of the headland, causing the waves to bend.
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What is refraction?
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the bending of waves due to a change in wave velocity
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How does wave refraction at headlands affect deposition and erosion?
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Wave refraction at the headland increases erosion at the headland and causes deposition in adjacent bays.
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In the long term, what do beach drift and longshore current do?
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Move sediment parallel to the shoreline
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What is the longshore current?
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water forced by waves to move along the shore
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Which way would sediment move if NO beach drift existed?
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at an angle to shore
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Surface ocean currents __________
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-are influenced by Coriolis effect
-are driven by winds
-form large rotating gyres in the major ocean basins
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Equatorial currents that are part of the subtropical gyres flow ___. Equatorial counter currents between the gyres flow ___ .
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east to west; west to east
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Cool ocean currents ___.
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generally flow from high latitudes towards the equator
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The subtropical gyres ___.
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play a large role in climate
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Deep ocean currents ___.
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result from changes in water density (due to temperature and salt content)
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Wave Period
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the inverse of wave frequency
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Relationship between wave period and wavelength
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Direct-waves with shorter periods have shorter wavelengths
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How would an object in Earth's atmosphere be deflected as a result of Earth's rotation?
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to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere
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What is the Coriolis effect?
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the deflection of objects to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere
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Which way would an airplane deflect if flying from the North Pole toward the equator?
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to the right, west
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Which way would an airplane deflect if flying from the South Pole toward the equator?
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to the left, east
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Which way would an airplane deflect if flying from the West Coast of the United States to the East Coast of the United States?
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to the south
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Which way would an airplane deflect if flying from the East Coast of the United States to the West Coast of the United States?
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to the north
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Which way would an airplane deflect if flying from the east coast of South Africa to the west coast of South Africa?
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to the south
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Which way would an airplane deflect if flying from the west coast of South Africa to the east coast of South Africa?
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to the north
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If the wavelength of a set of waves is 20 feet long, how deep is the wave base?
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10 ft below the surface
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How shallow must the ocean floor be for waves to start to break for a wave set with a wavelength of 20 feet?
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Waves will break when the ocean floor is 10 feet below the surface.
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When a longshore current meets a jetty
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Sediment is deposited on the up-current side of a jetty and eroded on the down-current side of a jetty.
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Which of the following describes the general pattern of movement of sand on a shoreline?
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Net sand movement is parallel to the shore.
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How does the tide cycle affect erosion along a sea coast?
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The tide cycle causes erosion to occur at different elevations along a sea coast.
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When waves approach shore and touch bottom, what happens to the wave form?
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wavelength decreases and height increases
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Which pattern of particle movement occurs when wave movement is oblique(slanted) to the beach?
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Particles move on the beach in a zigzag pattern.
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Which situation occurs in the downcurrent direction when a groin is constructed on a beach to prevent erosion of a beach by longshore currents?
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Sediment is removed on the downcurrent side of the groin.
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If the wave period changes so that it is half its original value, how does this change the wavelength?
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The wavelength will also be half as long.
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Which factors drive thermohaline circulation in the ocean basins?
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temperature and density
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What is the definition of the shore?
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that area along a coast that ranges from the lowest tide level to the furthest reaches of land affected by storm waves
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You are sitting in a beach chair, watching the waves roll in. From your perspective, how will the wave speed, length, and height change as the wave gets closer to your beach chair? Why?
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Because the seafloor is getting increasingly shallow, the wave speed and wavelength will decrease, whereas the wave height will increase.
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How do waves cause erosion in coastal environments?
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-sediment and shell fragments are carried by waves and erode with impact and abrasion
-force of wave impact against rock creates fractures and fragments
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How would you expect sediment to change as you walk from shore into the ocean?
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Sediment generally changes from sand to mud to limestone.
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How are changes in sea level recorded in rock?
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Rock type changes vertically.
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How did sea level change to produce this sequence of rocks?
[TOP: Sand, MID: Mud, BOTTOM: Limestone]
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sea level fell
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How did sea level change to produce this sequence of rocks?
[TOP: Limestone, MID: Mud, BOTTOM: Sand]
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sea level rose
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How did sea level change to produce this sequence of rocks?
[TOP: Limestone, MID1: Mud, MID2: Sand, BOTTOM: Mud]
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sea level fell and then rose
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How did sea level change to produce this sequence of rocks?
[TOP: Mud, MID1: Limestone, MID2: Mud, BOTTOM: Limestone]
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Sea level fell, then rose, and then fell again.
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Which rock types would you expect to be deposited on top of limestone if sea level falls and then rises?
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mud followed by limestone
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Which rock types would you expect to be deposited on top of limestone if sea level rises and then falls?
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limestone followed by mud
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Which rock types would you expect to see deposited if sea level rises and then falls?
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sand covered by mud covered by sand
