Landfill, Stratigraphy, and Geologic Time:
A Practical Application of the Principles of Stratigraphy
Forensic Geologists Use Scientific Laws to Indict Polluter
Aim: How can we practically apply the principles and methods by which earth scientists determine
geologic history to provide evidence of illegal dumping?
1. Students should be able to define and demonstrate an understanding and practical application of the
following vocabulary terms and the concepts they convey: uniformitarianism, sediment, stratum, (bed/layer/
horizon), strata, original horizontality, superposition, cross-cutting relationships, geologic column, relative
dating, absolute dating, geochronology, geologic time scale, fossil, index fossil, evolution, extinction, correlation,
hiatus, unconformity, faunal succession, and erosional surface.
2. Students should be able to demonstrate the ability to observe and interpret subsurface data by creating
an accurate stratigraphic column from written as well as physical sources and evidence.
3. Students should be able to demonstrate the ability to date, in relative and/or absolute terms, a vertical
succession of layered materials that has neither been overturned nor deformed.
4. Students should be able to demonstrate the ability to interpret the history, general sequence, and
chronology of events of a region by an investigation of a vertical succession of layered materials deposited at
the site over a specified period of time.
5. Students should be able to demonstrate the ability to follow instructions and sequence information.
The purpose of this laboratory activity is to provide the evidence necessary to either indict or exonerate a
suspected, notorious local polluter. This activity, therefore, should be thought of as a search for indisputable
evidence of illegal dumping to be used in court. Regents Earth Science and Geology students are required to
think and behave like detectives, searching for and interpreting clues, while being ever-mindful of the principles
of stratigraphy and methods by which earth scientists deduce geologic history (hence the term "forensic geology").
There are many similarities shared between the alternating layers of earth and rubbish in a landfill and the layers
of sedimentary strata which accumulated in a sedimentary basin, as well as the correspondence between fossils
and anthropogenically-produced solid waste. The extrapolation of buried newspapers, for instance, or any other
material which may give indisputable evidence of time of formation (perhaps even time of burial) and their
remarkable correspondence to index fossils should be clearly understood. Such an interpretation will assist you
in understanding the pivotal importance of these features in developing a chronology of events and thereby
interpreting the history of a given location based on the accumulation of everything from mineral detritus to
garbage, to many other types of surface materials that become buried and preserved at or near the Earth's
As the geologist works to develop a model of the Earth's history, he or she attempts to place events in
chronological order - that is - in order of which events happened first, then second, and so on. The geologist
attempts to find the relative age of a rock or event - its age compared with that of other rocks or events. The
geologist also attempts to find the actual, or absolute age, which is the date that an event occurred or a rock
Before we advance into a discussion of how earth scientists sequence past geologic events, there are three
basic principles, or "laws", of earth science that have arisen from a study of sedimentary rocks and processes
that should be restated. These laws are uniformitarianism, original horizontality, and superposition.
Uniformitarianism. Any discussion of geologic history, whether a period of hundreds or hundreds of millions
of years, necessitates analysis of features and description of events of the past in terms of contemporary
geologic processes. We assume that the forces at work on the Earth have not changed with time. Rivers, for
example, were not only present in the distant past but developed, behaved, and produced features in the same
fashion as modern river systems. Simply put, the uniformitarianist's credo as so eloquently stated by Scottish
geologist James Hutton over 200 years ago - "the present is the key to the past" - is the cornerstone of modern
geological thinking. Therefore, by observing the geologic processes now at work on the Earth, it is possible to
decipher geologic history as written in the textures, minerals, and fabrics of rocks.
Original Horizontality. Sedimentary rocks for from the deposition, compaction, and cementation of
sediments that settle through a column of fluid. Sediments that are generally deposited in slowly or nonmoving
fluids accumulate at the bottoms of rivers, lakes, oceans and terrestrial basins in flat, parallel, horizontal layers.
This tendency of most sediments deposited under such conditions (and not on sloping surfaces) is called
original horizontality. In other words, geologists assume, for the most part, that the individual layers or strata of
most sedimentary rocks were originally deposited as horizontal blankets on the bottom of a basin. Therefore the
individual rock layers, as well as their bounding surfaces, originally possessed a horizontal orientation
Superposition. If we accept the principle of original horizontality, it is simple to infer that in a vertical
succession of sedimentary strata that have neither been overturned nor otherwise strongly deformed, the oldest
layers reside at the bottom and the youngest layers rest at the top. This is the principle of superposition. Since
sedimentary strata resemble and are formed in much the same fashion as layers in a birthday cake, it is a
simple matter of logic to understand that the lowest (or relatively "oldest") layer of cake has to be deposited on
the plate first. Each new layer, therefore, is relatively younger than the layer beneath but older than each
subsequent layer. Superposition, therefore, allows the relative dating of sedimentary strata.
a. uniformitarianism _________________________________________________ b. sediment _______________________________________________________ c. stratum (bed/layer/horizon) _________________________________________ d. strata __________________________________________________________ e. original horizontality _______________________________________________ f. superposition ____________________________________________________ g. cross-cutting relationships _________________________________________ h. geologic column __________________________________________________ i. relative dating ____________________________________________________ j. absolute dating ___________________________________________________ k. geochronology ___________________________________________________ l. geologic time scale _______________________________________________ m. fossil ___________________________________________________________ n. index fossil ______________________________________________________ o. evolution ________________________________________________________ p. extinction _______________________________________________________ q. correlation ______________________________________________________ r. hiatus __________________________________________________________ s. unconformity ____________________________________________________ t. erosional surface _________________________________________________
one set of instructions and lab data one report sheet pencils with erasers colored pencils one box of labeled core material retrieved from the Swarm o'Seagulls Landfill (optional) one magnifying lens (optional)
Your first task is to plot an accurate stratigraphic column of the Swarm o'Seagulls site using your own
system of symbols or ornamentation to describe the content of material exhumed from each rubbish layer.
Accurately plot the data in the column space provided. Depths in 10-foot intervals have been provided for your
Your second task is to carefully study your evidence and try to determine if Big Louie has violated his
contract with the borough to stop dumping at the site after February 1, 1985 by strictly applying the three laws
of stratigraphy to your analysis of the subsurface materials excavated from the dump: uniformitarianism, original
horizontality, and superposition. Faunal succession may also be a helpful guide to interpretation. (Hint: You
should also try to think of some of the samples as index fossils that provide indisputable evidence of maximum
time of deposition or, in this case, the maximum time of dumping.)
The borough is counting on our expertise in stratigraphic analysis and "forensic geology" to help them
maintain a healthy environment for the people of southern Brooklyn. Bear in mind that Big Louie will have a team
of lawyers and his own consulting geologists standing by who will attempt to dismiss our evidence and refute our
claims if they are not in his favor. The success of our client's case depends upon how successfully we apply and
how stringently we adhere to our stratigraphic "laws" in the analysis of our data.
Good luck. We'll need your reports a.s.a.p. in order to prepare our final report for courtroom presentation.