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Quizzes > Science > Earth & Space Science

Gutenberg Discontinuity Quiz: Challenge Your Geology Know-How

Ready to explore the mantle-core boundary? Take this geology quiz now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration of Earth layers highlighting mantle core boundary for Gutenberg Discontinuity quiz on blue background

Ever wondered what lies between the mantle and core? Put your Earth science skills to the test with our free Gutenberg Discontinuity Quiz! This engaging geology quiz is crafted to challenge your understanding of the mantle-core boundary and reveal how well you grasp Earth's interior structure. Explore seismic wave behavior, compare the famous Lehmann discontinuity , and even warm up with a quick layers of the earth quiz before tackling the main challenge. Whether you're a dedicated geology enthusiast or just curious about what's happening miles beneath your feet, this quiz will sharpen your knowledge and leave you craving more. Ready to dive deep? Take the quiz now and see if you can ace the Gutenberg Discontinuity Quiz!

What is the Gutenberg discontinuity?
Boundary between Earth's outer core and inner core
Boundary between lithosphere and asthenosphere
Boundary between Earth's crust and mantle
Boundary between Earth's mantle and outer core
The Gutenberg discontinuity marks the boundary between the silicate mantle and the liquid iron outer core at about 2,890 km depth. It was identified by Beno Gutenberg through seismic wave studies, which show a sharp change in velocity. This boundary is crucial for understanding the layered structure of Earth's interior. source
At approximately what depth does the Gutenberg discontinuity occur?
Around 35 km
Around 660 km
Around 5,150 km
Around 2,890 km
Seismic data indicate that at roughly 2,890 km beneath the surface, there is a strong discontinuity in wave behavior marking the mantle-outer core boundary. This depth corresponds to the Gutenberg discontinuity. Recognizing this depth helps geoscientists map Earth's internal layering. source
The Gutenberg discontinuity is characterized by what change in seismic wave behavior?
Refraction of surface waves only
Sudden increase in P-wave velocity
Sudden disappearance of S-waves
Gradual decrease of both P- and S-waves
At the Gutenberg discontinuity, S-waves cannot travel through the liquid outer core and thus disappear, while P-waves slow down abruptly. This behavior helped uncover the liquid nature of the outer core. The loss of S-waves beyond 2,890 km provides direct evidence of a fluid layer. source
The outer core is composed primarily of which material?
Solid iron
Gaseous hydrogen
Silicate minerals
Liquid iron and nickel
Seismic wave velocities and densities indicate that the outer core is a liquid layer composed mainly of iron and nickel. Its liquidity is confirmed by the absence of S-waves. The metallic composition also generates Earth's magnetic field through convective motion. source
The discovery of the Gutenberg discontinuity helped scientists understand the existence of Earth's what?
Liquid outer core
Magma chambers
Magnetic field
Tectonic plates
By observing the abrupt change in seismic wave behavior at the Gutenberg discontinuity, scientists confirmed a liquid outer core. This discovery was key to explaining S-wave shadows and the generation of Earth's magnetic field through dynamo action. It also refined models of Earth's internal structure. source
Which seismic wave cannot travel through the outer core due to the Gutenberg discontinuity?
S-waves
Surface waves
P-waves
Rayleigh waves
S-waves (shear waves) cannot propagate through liquids, so they vanish beyond the Gutenberg discontinuity where the outer core is liquid. P-waves (compressional waves) continue but with reduced velocity. This absence of S-waves provided early evidence for a fluid layer. source
The change in density at the Gutenberg discontinuity is approximately from about 5,600 kg/m³ to:
3,000 kg/m³
7,600 kg/m³
9,800 kg/m³
10,500 kg/m³
Density jumps from roughly 5,600 kg/m³ in the lowermost mantle to about 9,800 kg/m³ in the outer core. This abrupt increase supports a change from silicate minerals to liquid iron alloy. Seismic and gravity data together constrain these values. source
Which scientist first proposed the existence of the core-mantle boundary later named the Gutenberg discontinuity?
Beno Gutenberg
Alfred Wegener
Harold Jeffreys
Inge Lehmann
Seismologist Beno Gutenberg identified the core-mantle boundary in 1914 by analyzing seismic phase arrivals and noting abrupt velocity changes. His work built on previous studies but was the first clear characterization of this discontinuity. The boundary now bears his name as the Gutenberg discontinuity. source
The pressure at the Gutenberg discontinuity is approximately:
24 gigapascals
136 gigapascals
50 gigapascals
300 gigapascals
At about 2,890 km depth, pressures reach roughly 136 GPa. This immense pressure influences the phase and density of materials at the mantle-core boundary. High-pressure experiments and seismic models both support this estimate. source
The seismic discontinuity at the Gutenberg boundary is primarily due to changes in:
Temperature gradients only
Chemical composition
Magnetic properties
Gravitational field
The Gutenberg discontinuity arises from a change in composition - from silicate minerals to a liquid iron-nickel alloy - more than just temperature change. This compositional shift causes the abrupt seismic velocity change and the disappearance of S-waves. Identifying composition is essential to interpreting seismic data. source
How does P-wave velocity change when crossing from the lowermost mantle into the outer core?
It decreases sharply
It remains constant
It oscillates unpredictably
It increases sharply
Upon entering the outer core, P-wave velocity drops abruptly by about 10%, reflecting a transition from solid mantle to liquid metal. This decrease was a key observation for confirming the outer core's fluid state. Seismic refraction and reflection studies detail this velocity change. source
Which seismic phenomenon is a direct consequence of the liquid outer core inferred from the Gutenberg discontinuity?
Earthquake shadow zones
Generation of the magnetosphere
Plate tectonics
Deep-focus quake uplift
The liquid outer core creates an S-wave shadow zone (no S-waves transmitted) and a P-wave shadow zone due to refraction. These shadow zones occur opposite earthquake epicenters and provided early proof of a fluid core. They remain classic evidence in seismology. source
What role do light elements (e.g., sulfur, oxygen) play in the outer core around the Gutenberg discontinuity?
They increase the density beyond pure iron
They generate radiogenic heat
They reduce the melting temperature of the alloy
They block P-wave propagation
Incorporation of light elements such as sulfur and oxygen into the iron-nickel outer core lowers the melting point of the alloy under high pressure. This facilitates a liquid state at core-mantle boundary conditions. Geochemical models and high-pressure experiments support this compositional effect. source
The layer just above the Gutenberg discontinuity in the lowermost mantle is called:
Transition zone
D'' layer
Mohorovicic discontinuity
Asthenosphere
The D'' (D double-prime) layer lies immediately above the core-mantle boundary and exhibits complex seismic features. It represents the bottommost portion of the lower mantle above the Gutenberg discontinuity. This region is of keen interest for its thermal and compositional anomalies. source
Seismic anisotropy observed in the D'' layer above the Gutenberg discontinuity suggests what about the lowermost mantle's mineral structure?
Pure iron structure
Presence of liquid pockets
Random orientation of minerals
Alignment of bridgmanite crystals due to flow
Anisotropy in the D'' region indicates that bridgmanite, the dominant lower mantle mineral, is aligned by shear flow near the core-mantle boundary. This alignment alters seismic wave speeds depending on direction. It provides insights into mantle circulation and thermal patterns. source
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Study Outcomes

  1. Understand the Gutenberg Discontinuity -

    Define the mantle-core boundary and describe its fundamental characteristics, including its depth and composition.

  2. Identify seismic wave behaviors -

    Recognize how P-waves and S-waves change velocity and path when encountering the mantle-core boundary.

  3. Analyze variations in Earth's interior layers -

    Differentiate between the physical and chemical properties of the mantle and the outer core.

  4. Evaluate the significance of the mantle-core boundary -

    Explain its impact on geodynamic processes and the generation of Earth's magnetic field.

  5. Apply knowledge to quiz questions -

    Use your understanding of Earth's interior to answer quiz questions accurately and reinforce key concepts.

  6. Recall key facts about the Gutenberg Discontinuity -

    Memorize important data such as the discontinuity's approximate depth, seismic signatures, and role in geology.

Cheat Sheet

  1. Depth and Discovery of the Gutenberg Discontinuity -

    German seismologist Beno Gutenberg first identified the mantle - core boundary at roughly 2,900 km depth using P- and S-wave arrival times. A handy mnemonic is "Go at 2.9" (Gutenberg at 2.9 × 10³ km) to cement this key depth in your mind. This discovery is detailed in USGS and Berkeley Earthquake Science Center resources.

  2. Seismic Wave Behavior at the Mantle-Core Boundary -

    At the Gutenberg Discontinuity, S-waves vanish entirely because the outer core is liquid, while P-waves form a shadow zone beyond 104° - 140° from an earthquake epicenter. The P-wave velocity drop from ~13.6 km/s in the lower mantle to ~8.1 km/s in the outer core offers a classic example of Δv revealing state changes. Consult the Preliminary Reference Earth Model (PREM) by Dziewonski & Anderson for detailed velocity profiles.

  3. Composition and Physical State Contrast -

    The solid silicate mantle (olivine, pyroxene) gives way to a molten iron-nickel alloy in the outer core, often enriched with light elements like sulfur and oxygen. Temperatures at the boundary span ~3,900 °C, rising above 5,000 °C deeper in the core, a fact confirmed by high-pressure lab experiments at the Carnegie Institution. This sharp change in density and phase underpins the fundamental nature of the Gutenberg Discontinuity.

  4. Geodynamic and Magnetic Significance -

    Convection in the liquid outer core generates Earth's magnetic field through the geodynamo process, making the Gutenberg Discontinuity essential for sustaining our magnetosphere. Heat transfer across this boundary also drives mantle plume upwellings, influencing volcanic hotspots like Hawaii - a perfect quiz example linking deep-Earth physics to surface geology. Studies in Geophysical Research Letters highlight this coupling between core processes and surface phenomena.

  5. Modern Detection and Imaging Techniques -

    Seismic tomography uses global seismograph networks to produce 3D images of the Gutenberg Discontinuity, revealing undulations of tens of kilometers. Reflective studies using core-reflected PcP waves offer precise depth estimates, analogous to sonar mapping in the ocean's depths. Explore IRIS (Incorporated Research Institutions for Seismology) for interactive tomography maps to boost your earth's interior quiz prep.

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