earth science

Wissahickon Formation

Wissahickon Formation is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Wissahickon Formation rather than just read about it. In short: The Wissahickon Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and Delaware. It is named for the Wissahickon gorge in Fairmount Park, Philadelphia.

Key takeaways

Wissahickon Formation belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Wissahickon Formation to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Wissahickon Formation from memory before moving on to harder problems.

Reference excerpt

The Wissahickon Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and Delaware. It is named for the Wissahickon gorge in Fairmount Park, Philadelphia. In Maryland formations, the term "Wissahickon" is no longer used. Rocks in this classification have since been divided into several units, such as Lower Pelitic Schist and Prettyboy Schist.

Description The Wissahickon is described as a pelitic schist and gneiss with interlayers of quartzite. Color is highly variable as is the mineralogy. A general description for the unit is a silver to brown garnet mica-schist.

Metamorphic grade The highly variable nature of this rock type is also why the metamorphic grade is also complex. The existence of the minerals biotite, garnet, staurolite, and kyanite all imply a low-intermediate to high metamorphic grade. The metamorphic facies, which is described as lower to upper amphibolite facies, implies a moderate to high metamorphic temperature and a moderate pressure.

Age

Depositional age The age indicated on the most recent geologic map of southeast Pennsylvania shows the Wissahickon being Ediacaran to Cambrian in age. This age is a relative date since the sediments that created the Wissahickon are highly deformed and went through several deformation events.

Deformation age The sediments of the Wissahickon were altered during the Taconic orogeny and most dates do not place the deformation older than the Silurian. Although there is some evidence of Devonian-aged deformation.

Divisions The current map sought to divide the Wissahickon into three informal units. The type described here has been the restricted Wissahickon, or its easternmost section that exists in the City of Philadelphia and eastern Delaware County. The Glenarm Wissahickon and Mt. Cuba Wissahickon are two units described in western Delaware and Chester Counties, Pennsylvania. The metamorphic and depositional histories of these two series are different from the Wissahickon type described here.

Economic uses Wissahickon schist is quarried as a building stone and is used primarily as a decorative stone rather than a weight bearing stone. However, there are numerous old buildings in the Philadelphia area that are constructed almost entirely of this rock.

Illustrations

Worked examples

Example 1 — a first encounter with Wissahickon Formation

Start with the simplest possible case. Write down what Wissahickon Formation claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Wissahickon Formation before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Wissahickon Formation ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Wissahickon Formation

In research: Wissahickon Formation appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Wissahickon Formation in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Wissahickon Formation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cambrian System of North America, Ediacaran United States, Geologic formations of Delaware, so understanding it makes those chapters shorter.
In everyday life: Look for Wissahickon Formation outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Wissahickon Formation in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Wissahickon Formation means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Wissahickon Formation out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Wissahickon Formation in simple terms?

The Wissahickon Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and Delaware. It is named for the Wissahickon gorge in Fairmount Park, Philadelphia.

Why does Wissahickon Formation matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Wissahickon Formation?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Wissahickon Formation.