geography questions

Oceanography 101 LAB 3 Saunders Ocean Sediments & Bathymetry Name:___________________________ 1. Sediments (to be done in lab) (1.1 ) At each table should be a set of sediment slides containing various sediments from around the world. Examine the prepared sediments slides and determine their characteristics by filling out the table below. Slide Description Type Sorting A B C D E Oceanography 101 LAB 3 Saunders F G (1.2 ) After you have completed the table, check your results against a key provided by your instructor. Which sediments are more influenced by land processes (erosion, rivers, etc). Explain. __________________________________________________________________ _________ ___________________________________________________________________________ ___________________________________________________________________________ (1.3 ) Given what we’ve learned about sediments and their sources, would you guess th at the sediments of Puget Sound, which has 16 major and many minor rivers draining into it, are more terrigenous , biogenous , hydrogenous , or cosmogenous ? Explain. ___________________________________________________________________________ _____________________ ______________________________________________________ ___________________________________________________________________________ 2. Core Sample (2.1) By studying the sediments on the ocean floor, we can gather clues about what surface conditions were like at various times in the Earth's past when the sediments were deposited. Using those clues, we can try to reconstruct what might have happened during the Earth's past. As the particles pile up on the ocean floor, they begin to exert pressure on the sediments below. What do you think will happen to these sediments over time? Explain.__________________________________________________________ __________________________________________________________________________ ___________________________________ _______________________________________ (2.2) Below is a 6 m long core sample taken from the deep sea floor off shows fine grained mud layers alternating with sandier layers. The volcanic ash at the bottom is dated as 7700 years old (after Adams, 1990). How many alternating sand -mud layers do you count? __________________________________________________________________________ (2.3) How can you explain these alternating course, sandier layers with fine particle mud layers? (HINT: Note that this sample c ore was taken in a submarine canyon)___________________ ___________________________________________________________________________ ___________________________________________________________________________ _________________________________________________ __________________________ Oceanography 101 LAB 3 Saunders (2.4) Given the location of the core sample and its proximity to the Cascadia Subduction Zone, these alternating sandy -mud silt deposits are probably caused by megathrust earthquakes. A megathrust earthquake occurs where one tectonic plate is forced under (subducts) another.

Due to the shallow dip of the plate boundary, these earthquakes are among the world's largest, with moment magnitudes (Mw) that can exceed 9.0. So how many megathrus t earthquakes have we had in this region over the past 7770 years?______________________ 3. Hood Canal Bathymetry INTRODUCTION: If you haven’t heard the news lately, Hood Canal is in trouble. Large inputs of non -point and point source runoff and have lead to low oxygen environments especially in the deeper basins of Dabob Bay and Hoodsport . Let’s examine the bathymetry of Hood Canal to see if it can lend any clues as to why th is particular part of Puget Sound is so impacted. Core sample site Oceanography 101 LAB 3 Saunders (3.1) Obtain a map of Hood Canal. What is the scale on the map?_________________________ (3.2) What unit are the depth measurements?______________ (3.3) Obtain a straight edge and a pencil. Starting out near the opening of Hood Canal (near Admiralty Inlet) draw a light pencil line down the center of the canal using a straight edge, changing direction as the canal varies. Continue drawing a center line th e entire length of Hood Canal all the way to Lynch Cove . How many nautical miles long was your line?_________ ______________________________________________________________________________ (3.4) If you were to divide your line into 30 increments, how man y nautical miles would each increment be?__________________________________________________________________ (3.5) Estimate the depth at each of the 30 points and fill in the table below. Remember to make depth numbers negative. Using Excel or other spreadsheet program , plot the bathymetry of Hood Canal along your line with a 30 increment setting (i.e. divide your line into 30 equ al points and plot each point with the depth in fathoms ). Include a print out of the graph with this lab making sure you have a title, description and pr operly labeled axes. Transect Depth in _____ Transect Depth in _____ 1. 16. 2. 17. 3. 18. 4. 19. 5. 20. 6. 21. 7. 22. 8. 23. 9. 24. 10. 25. 11. 26. 12. 27. 13. 28. 14. 29. 15. 30. (3.6 ) Describe the overall shape of Hood Canal’s bathymetry.____________________________ __________ ____________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ (3.7) What is the origin of th e Hood Canal Basin (i.e. how did it form?)____________________ ______________________________________________________________________________ Oceanography 101 LAB 3 Saunders (3.8) Are there any features of Hood Canal’s bathymetry that your group can see that might influence its circulat ion ? Explain._________________________________________ _________ ______________________________________________________________________________ ______________________________________________________________________________ ___________________________________ ___________________________________________ ______________________________________________________________________________ (3.9) Locate on your bathymetric drawing of Hood Canal a inlet named Dabob Bay. This area has been in the news recently as a place i n trouble because of pollution and nutrient runoff from the surrounding farmlands and urban areas. Is there anything that you can see from its bathymetry that might indicate it has a particular susceptibility to these problems? Explain. _________________ _____________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ _______________________________________ _______________________________________ ______________________________________________________________________________