earth science

Sima (geology)

Sima (geology) 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 Sima (geology) rather than just read about it. In short: In geology, sima () is an antiquated blended term for the lower layer of Earth's crust. This layer is made of rocks rich in magnesium silicate minerals.

Key takeaways

Sima (geology) 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 Sima (geology) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sima (geology) from memory before moving on to harder problems.

Reference excerpt

In geology, sima () is an antiquated blended term for the lower layer of Earth's crust. This layer is made of rocks rich in magnesium silicate minerals. Typically, when the sima comes to the surface, it is basalt, so sometimes this layer is called the 'ocean layer' of the crust. The sima layer is also called the 'basal crust' or 'basal layer' because it is the lowest layer of the crust. Because the ocean floors are mainly sima, it is also sometimes called the 'oceanic crust'. The name 'sima' was taken from the first two letters of silica and of magnesia. Comparable is the term sial (another antiquated blended term), which is the name for the upper layer of Earth's crust (continental crust), namely rocks rich in aluminium silicate minerals.

Petrology The sima has a higher density (2800 to 3300 kg/m3) than the sial, which is due to larger amounts of iron and magnesium, and smaller amounts of aluminium. When the denser sima comes to the surface it forms mafic rocks, or rocks with mafic minerals. The most dense sima has less silica and forms ultramafic rocks.

See also Asthenosphere Eduard Suess KREEP Lithosphere Earth's mantle

References

Bates, R.L., and Jackson, J.A., (1987) Glossary of geology American Geological Institute, Alexandria, Virginia. Cottingham, Kenneth. “The Geologist's Vocabulary.” The Scientific Monthly, vol. 72, no. 3, 1951, pp. 154–163. JSTOR, https://www.jstor.org/stable/20222. Accessed 19 June 2020. Dilek, Y. and Newcomb, S. (eds.) (2003) Ophiolite Concept and the Evolution of Geological Thought Geological Society of America Special Paper 373, Boulder, Colorado.

Illustrations

Worked examples

Example 1 — a first encounter with Sima (geology)

Start with the simplest possible case. Write down what Sima (geology) 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 Sima (geology) 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 Sima (geology) 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 Sima (geology)

In research: Sima (geology) 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 Sima (geology) 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: Sima (geology) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earth's crust, Petrology, Structure of the Earth, so understanding it makes those chapters shorter.
In everyday life: Look for Sima (geology) 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Sima (geology)” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Sima (geology) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sima (geology) 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 Sima (geology) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sima (geology) in simple terms?

In geology, sima () is an antiquated blended term for the lower layer of Earth's crust. This layer is made of rocks rich in magnesium silicate minerals.

Why does Sima (geology) 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 Sima (geology)?

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 Sima (geology).