earth science

Gutenberg discontinuity

Gutenberg discontinuity 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 Gutenberg discontinuity rather than just read about it. In short: The Gutenberg discontinuity occurs within Earth's interior at a depth of about 2,900 km (1,800 mi) below the surface, where there is an abrupt change in the seismic waves (generated by earthquakes or explosions) that travel through Earth. At this depth, primary seismic waves (P waves) decrease in velocity while secondary seismic waves (S waves) disappear completely.

Key takeaways

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

Reference excerpt

The Gutenberg discontinuity occurs within Earth's interior at a depth of about 2,900 km (1,800 mi) below the surface, where there is an abrupt change in the seismic waves (generated by earthquakes or explosions) that travel through Earth. At this depth, primary seismic waves (P waves) decrease in velocity while secondary seismic waves (S waves) disappear completely. S waves shear material, and cannot transmit through liquids, so it is believed that the unit above the discontinuity is solid, while the unit below is in a liquid, or molten, form. This distinct change marks the boundary between two sections of the earth's interior, known as the lower mantle (which is considered solid) and the underlying outer core (believed to be molten). The molten section of the outer core is thought to be about 700 °C (1,300 °F) hotter than the overlying mantle. It is also denser, probably due to a greater percentage of iron. This distinct boundary between the core and the mantle, which was discovered by the change in seismic waves at this depth, is often referred to as the core–mantle boundary, or the CMB. It is a narrow, uneven zone, and contains undulations that may be up to 5–8 km (3.1–5.0 mi) wide. These undulations are affected by the heat-driven convection activity within the overlying mantle, which may be the driving force of plate tectonics-motion of sections of Earth's brittle exterior. These undulations in the core–mantle boundary are also affected by the underlying eddies and currents within the outer core's iron-rich fluids, which are ultimately responsible for Earth's magnetic field. The boundary between the core and the mantle does not remain constant. As the heat of the earth's interior is constantly but slowly dissipated, the molten core within Earth gradually solidifies and shrinks, causing the core–mantle boundary to slowly move deeper and deeper within Earth's core. The Gutenberg discontinuity was named after Beno Gutenberg (1889–1960) a seismologist who made several important contributions to the study and understanding of the Earth's interior. It has also been referred to as the Oldham–Gutenberg discontinuity (after Richard Dixon Oldham), or the Wiechert–Gutenberg discontinuity (after Emil Wiechert).

See also Lithosphere–asthenosphere boundary Mohorovičić discontinuity

References

Worked examples

Example 1 — a first encounter with Gutenberg discontinuity

Start with the simplest possible case. Write down what Gutenberg discontinuity 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 Gutenberg discontinuity 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 Gutenberg discontinuity 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 Gutenberg discontinuity

In research: Gutenberg discontinuity 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 Gutenberg discontinuity 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: Gutenberg discontinuity is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earthquakes, Seismology, so understanding it makes those chapters shorter.
In everyday life: Look for Gutenberg discontinuity 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 “Gutenberg discontinuity” →

Affiliate

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

How to study Gutenberg discontinuity in 20 minutes

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

Frequently asked questions

What is Gutenberg discontinuity in simple terms?

Why does Gutenberg discontinuity 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 Gutenberg discontinuity?

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 Gutenberg discontinuity.