Transcript 4 Plate Tectonics & Paper

Seismic waves bounce off layers
• Based on Chemistry
• Mohorovicic discontinuity Moho
–Between crust and mantle
• Gutenburg discontinuity
–Between mantle and core
Oceanic Crust
Continental Crust
Moho
Discontinuity
Gutenburg
Discontinuity
Another View of
Earth’s structure
Two types of crust
• Continental
– Thick 20-90 km thick
– Lower density 2700 kg/cubic meters
– Si, O, Al, Fe, Mg….
• Oceanic
– Thin 5-10 km thick
– More dense 3000 kg/cubic meters
– Fe, Mg, O, Si, Al…
Theory of Plate Tectonics
• Using this understanding we have
developed a model for how the Earth
behaves
• This model helps us understand a variety of
environmental hazards
Scientific Theories are:
• Based on observations of physical
things
• Developed from hypotheses that
explain the observations
• Developed from hypotheses that have
been tested
• What is the scientific method?
• An example the Theory of Continental
Drift
Alfred Wegener (1880 – 1930)
Theory of Plate Tectonics
• Theory of Plate Tectonics
• Types of plate boundaries
– Divergent
– Convergent
– Transform
• How the theory came about
Plate Tectonics
• Three types of plate boundaries
• Divergent
– Oceanic-Oceanic Mid Ocean Ridges
– Continental-Continental Rifts
• Convergent
• Transform
1st
2nd
3rd
Plate Tectonics
• Three types of plate boundaries
• Divergent
• Convergent
– Oceanic-Oceanic
– Continental-Oceanic
– Continental-Continental
• Transform
Plate Tectonics
•
•
•
•
Three types of plate boundaries
Divergent
Convergent
Transform
– Oceanic-Oceanic
– Continental-Continental
So all together now
Plate Tectonics
Plate Tectonics
180 million years ago
70 million years ago
Today
Evidence for Plate Tectonics
• Ocean depths – the worlds oceans are not
deepest in the center and shallow at the
edges as you would expect in a world w/out
Plate Tectonics. Instead the deepest
portions of the oceans are along the ocean
edges and shallow mountain ranges are
located in the center of many of our oceans.
Bathymetric Map of the Earth’s Oceans
Evidence for Plate Tectonics
• Paleomagnestism – the magnetic field of the
Earth changes with time, indeed there are
reversals in this magnetic field over time.
Evidence of this is preserved in the newly
created oceanic crust.
Evidence for Plate Tectonics
• Volcanic Island Chains – the presence of
linear volcanic island chains indicate the
movement of plates over a stationary
convection source (hotspot).
Your Paper
• Look at the handouts I provided for the paper
– The first outlines the assignment
(Writing Assignment #2)
– The second outlines the elements of a paper
(Grading Checklist for Geology…)
• What should be in the paper?
–
–
–
–
–
Format
Introduction
Body of the paper
Conclusions
References (for the 2nd paper only)
Your Paper cont. (1)
• Format
– Title page (with name, course & section)
– Have a brief table of contents (include a list of illustrations if you
have them)
– Page number your paper
• Introduction
– Describe your papers topic, or question to be answered clearly
– Outline the main topics you are covering in the intro
• Body of Paper
– Make sure your writing is well organized – does the flow of
thoughts follow a logical sequence that makes sense?
– Have clear and logical transitions from one idea to the next
– Proofread and rewrite your paper it shows when I grade it
• Conclusion
– Explain the importance of your topic or relate it to Envir. Geology
– Summarize the points covered in your paper
Your Paper cont. (2)
• References
– References allow the reader to lookup the sources you used for your paper
– References follow a regular format, I’ve given you examples of APA
format reference styles with your syllabus, USE THEM
– Example:
Johnson, Dave (1981). Mt. Saint Helens. USGS Professional Paper
#89. United States Geological Survey, August
Merritt, James (2005). Mountain of Death, Mt. St. Helens. [online]
Available: http://www.mysite.edu/sillysite/info.htm [24 December, 2005].
• Citations
– If you are using information in your paper from a source other than
yourself (even from personal source, in conversation) you need to
reference it at the end of your paper, and cite it in the text - right after
you’ve used it in the paper.
– Citations are generally done by giving the author/organization name and
year. Examples:
(Johnson, 1981) or (Merritt, 2005) or for an organization (USGS, 1980).
– They go at the end of the sentence or paragraph just before the period.