The Meridian Basin Group
You had two principal accomplishments this quarter. They include
(1) You added better definition to our mapping of the north slope of the basin, by adding data from
the two borehole samples which you took.
(2) You extended our mapping westward to include the area of the Police Station, using data
generated years ago when the station was built.
By this process you have produced the first complete map of the Meridian Avenue Basin, which
is a significant contribution to the scientific study of this area. This follows the mapping of the
smaller 103rd Street Basin, which was completed last spring (Studer-Ellis, 2014). It is an
important milestone in our overall plan to map the campus and the larger Northgate Basin.
In addition to this mapping project, you also collected data on some of the material filling the basin. This
is part of an on-going inventory of the sub-surface geology, and your observations join perhaps a
hundred others in this data-base. This includes the (routine) analysis of the core retrieved from site 9202.
Finally, you were the first to assess the water-holding capacity of the peat which fills much of the
Meridian Basin. This data can be used by future researchers to estimate the total water-holding
capacity of the basin, an important component in the local hydrologic setting.
Introduction:
You should start out by indicating that this is a study on the Meridian Avenue Basin (credit the name to
Weaver, Stephen and Myers, Shaina 2014: The Meridian Avenue Basin Unpublished student research,
Geology 208 Summer Quarter 2014 North Seattle College), and describe what is and where it is (you can
get a good idea on this from the poster by Studer-Ellis).
You will then have to give some general information on the glacial history of the area. It is sufficient to
say that when the icecap retreated, it left behind a layer of advance outwash (Esperance) sand overlain
by glacial till. You can find references for these materials in the text copy from the Northeast Seattle
Map (on your disc). In this area, you can point out that previous researchers have found that these
basins are floored in glacial till, and are largely filled with silt and peat deposits. They have further
suggested that they appear to have been depressed into the landscape, at a time after the till was
deposited (cite Suder-Ellis and Weaver and Myers).
You can then briefly summarize our theory of how icebergs floating in the waters of glacial lake Russell
were deposited in the post-glacial waters of Thornton Lake, perhaps 13,500 years ago. We theorize
that these icebergs sank into the water-saturated sediments of the lake, creating these depressions ( for
this you can cite: Personal communication: John Figge, Instructor, NSC). You should provide some
measure of detail on this.
You can then summarize the purpose of your research, in terms of the questions it seeks to answer (see:
above). You can then note that this is part of a larger on-going project to map the campus and the
surrounding areas, and that it builds on the research of previous students over the past several years.
Method:
You have several different procedures to describe:
(1) Core –sampling. You need to describe how this was done, detailing the type of pipe (thin-walled
EMT electrical conduit, 2”) and impact driver (a 10-pound sledge hammer). You need to detail
how it was driven, and how it was retrieved. Note that it was driven “to resistance” – meaning
that no further movement was noted after extended driving.
Note that the pipe was cut open, that the cross—section revealed two distinct sections, and that
they were rendered for analysis.
(2) Sediment analysis. You have two fractions from 92-02 (upper and lower) which you analysed.
Detail how the analysis was conducted.
(3) Peat analysis: Describe the process by which you obtained the water-holding capacity of the
peat (per cubic inch). You can note that the sample was from site 91-01. The samples were
baked at 300 degrees for several hours, which is a standard procedure.
Results:
Give your data here.
Two borehole samples: how far down to glacial till? Give these figures in real elevations
Note that these figures were added to the existing map, which was modified to fit the
new data.
You should have a figure of that modified map.
You can then note that we obtained archived data from the construction of the Police
Station, which we used to extend that map westward (cite the source for this
information, it is a geotechnical study in the “local soils reports” section under “campus
geology” on your disc.
You should provide a figure of that extending mapping.
Two sediment samples: give a complete analysis for each
Peat samples: give the results of your analysis
Discussion Section:
Given what we knew, and what we now know, what does all of this mean? Does this support our theory
of how the basins were formed? What does it imply for ground conditions in the area, for hydrology,
for potential development? How does this compare with the previously-studied 103rd street basin?
Etc, etc, etc
Conclusions:
Restrict this to your conclusions on the basin, and the water-holding capacity of the peat. For the basin,
give an estimate of its size and depth. Note that this is a larger version of the previously studied 103rd
street basin (cite), and that it represents a significant step in a larger program of campus-wide mapping.
Finally, suggest directions for future research. Where do we go from here??