Download Oceans and Continental Profiles Activity

Name_________________________________Block:____Date_____
Check class website for hints and changes on handouts.
ES1 Ocean Floor and Continental Profiles Act #4
Introduction: The ocean floor can be mapped with precision by using depth recorders aboard oceanographic survey ships. These
recorders reflect sound waves off the ocean floor and receive the returning echoes as the ship moves across the ocean’s surface.
By determining the time it takes for the echoes to return, scientists can determine the depth of the ocean floor. In this activity you will
look at profiles of the Atlantic and Pacific Ocean floors and one of the land surface across the United States. Makeup problems only
needed for incorrect or missing answers after class discussion.
Pre Activity Thinking:
Profiles are cross-sectional views of underwater or land surface features. (seen from the side) They are made by plotting
ocean depth & land elevation in meters versus horizontal distance in kilometers. The vertical scale exaggerates the steepness of
mountains so that you can see them on these drawings, & is much larger than the horizontal scale. Zero on the vertical scale is
equal to sea level. How many kilometers deep is shown in the first profile?_______ How would the profile shape change with no
exaggeration?_________ _____________________________ To see this, mark & label sea level on the profile as if there were no
vertical exaggeration from 6000 m, or 6 km, depth ( as if 6km vertically were on the same scale as 6 km horizontally). done_
This profile is the Atlantic Ocean floor from S. America to Africa. The shape of the ocean floor is caused by its formation. When tectonic plates separate at a diverging boundary, magma wells up to create both a mountain range and new ocean floor along the middle of an ocean. Use the index to find the following ideas. From the textbook diagrams (not just the glossary), briefly describe them
in your own words, including how these features are formed : Makeup--include more details in your own words
1. Review your knowledge: rift valley--describe its shape, location, and plate movement. pg.:____
2. mid-ocean ridge. describe its shape, plate movement, and source of rock which forms it. pg.:____
Plate
Tectonics
shelf about 500m below sea level
kilometers
1. What is the greatest depth shown on this profile? (give unit)___________
Makeup (do only for missing or incorrect answers): depth of A______
2. How far below sea level is the tallest peak in the Mid-Atlantic Ridge?________(give unit)___ Makeup: point B_____
3. There is a rift valley cutting through the Mid-Atlantic Ridge, but the vertical exaggeration makes it hard to see. Mark & label
where you think it is on the profile, and check here_______ Which side (compass direction) of the ridge is lower?
_________________Makeup: explain how the scale makes the rift appear so narrow
Use your textbook reading to explain in your own words (not from glossary): Makeup, explain well with more detail
1. Sea mount. height pg.:____
2. Convergent boundary/Subduction Zone: describe plate movement pg.:____
How does the density of the 2 types of crust affect the subduction zone?
yay, bonus pt. because ________
oops, no HO, book, heading on
this date______=MP
3. Divergent boundary: describe plate movement pg.:____
Which boundary type would have a steep drop-off right next to a continent?_______________________
Which boundary type would have a more gradual drop-off including a continental shelf? ______________________
Makeup: explain why
Pg. 1 of 2 ES1 Ocean & Continental Profiles ASF 3/14/16 3:00 PM
The next profile is of the Pacific Ocean floor from the Island of Hawaii to Los Angeles, California.
profiles available in class
A
1. What is the greatest depth? (give unit)________Makeup: A
2. Circle the 1st 50 km (not far on this scale!) on the right of the Atlantic and Pacific Ocean profiles, just at the top, looking at the
slopes of the boundaries near the continent. Compare the steepness of the continental margin at Los Angeles to that of the South
American and African plates on p. 1 Which ocean has a flattish area?______________What is that feature called?
_____________________________________Makeup: explain is happening at each boundary
3. What kind of boundary exists near Los Angeles? (See map p. 248 & remember Atlantic is growing & Pacific is getting smaller )
____________________What is the movement of the oceanic crust at this boundary compared to continental crust?
_______________ How does this explain the difference in #2?
Makeup: explain why why boundaries at S America and Africa not steep.
4. Remember that the vertical scale is greatly exaggerated. Mark & label on the profile where seamounts might be. Done__
Makeup: explain why seamounts so narrow on profile:
5. What is the height of the tallest seamount as measured from the ocean floor?_______________ Makeup: second tallest______
The last profile shows the land surface across the United States.
profiles available in class
1. What is the height of the tallest peak?______________ Makeup: Appalachians
2. Which mountains on the diagram are the lowest in the US?___________________________________ Makeup: explain cause
(think about age of mountains)
3. From sea floor to summit, what is the height of the Island of Hawaii?__________________ The Rocky Mountains?
_____________ Which is higher?____________ What might be an explanation for this difference?-(think about their ages)?
Makeup: compare heights Hawaii to Sierra Nevada & explain why
total wrong/24 @ 4______ grade = _________ F, Ex, Complete & appropriate MU for____ MCGC CIC L FL Forgot grade abbreviations?
See class sign, Ipass progress report “comments to class”, ES1 or ES2 home pages on Mrs. S-Fs website. Do corrections in another color.
Pg. 2 of 2 ES1 Ocean & Continental Profiles ASF 3/14/16 3:00 PM