Earth's Interior and Energy Accumulation
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Questions and Answers

What is the mineral that undergoes pressure-dependent transformation under Earth's interior?

  • Pyroxene
  • Feldspar
  • Quartz
  • Olivine (correct)

    • Which of the following minerals is NOT a product of olivine's transformation under pressure?

  • Pyroxene (correct)
  • Perovskite
  • Ringwoodite
  • Wadsleyite

    • What is the name of the mineral found in meteorites and some rare rocks, which forms under extreme pressure?

  • Perovskite
  • Ringwoodite (correct)
  • Pyroxene
  • Wadsleyite

    • What is the depth at which the first phase transformation of olivine occurs?

    <p>410 km (A)</p> Signup and view all the answers

    What is the mineral that olivine transforms into at the second phase transformation?

    <p>Perovskite (B)</p> Signup and view all the answers

    What are the two main sources of heat in Earth's interior?

    <p>Radiogenic heat and primordial heat (C)</p> Signup and view all the answers

    What is the largest contributor to Earth's heat flow?

    <p>Radiogenic heat (B)</p> Signup and view all the answers

    Which of the following is NOT a type of heat transfer in Earth's interior?

    <p>Radiation (C)</p> Signup and view all the answers

    How does the density of a rock affect the speed of seismic waves?

    <p>Denser rocks cause seismic waves to travel faster. (B)</p> Signup and view all the answers

    The low velocity zone (LVZ) is characterized by which of the following?

    <p>Partial melting of olivine and pyroxene. (B)</p> Signup and view all the answers

    What is the primary reason for the decrease in S-wave velocity at the base of the lithosphere?

    <p>The presence of a large amount of molten rock. (D)</p> Signup and view all the answers

    What is the name of the boundary between the Earth's crust and the mantle?

    <p>Moho Discontinuity (B)</p> Signup and view all the answers

    What happens to olivine as it transitions from the upper mantle to the lower mantle?

    <p>It undergoes a phase change to a denser, more closely packed structure. (D)</p> Signup and view all the answers

    What is the geotherm?

    <p>A curve that describes the temperature of the Earth's interior. (D)</p> Signup and view all the answers

    What is the primary source of the basaltic magma that erupts on the Earth's surface?

    <p>The LVZ in the upper mantle. (B)</p> Signup and view all the answers

    What type of seismic waves are used to determine the depth of the Earth's layers?

    <p>P-waves and S-waves (A)</p> Signup and view all the answers

    What is the approximate depth of the boundary between the Earth's outer and inner core?

    <p>5150 km (B)</p> Signup and view all the answers

    What type of wave is completely absent in the Earth's outer core?

    <p>S-waves (A)</p> Signup and view all the answers

    What is the primary reason for the sharp change in wave speed at the core/mantle boundary?

    <p>A change in the mineral composition of the Earth. (C)</p> Signup and view all the answers

    What is the primary composition of the Earth's core?

    <p>Iron and nickel (D)</p> Signup and view all the answers

    What is the reason for the density contrast between the mantle and the core?

    <p>The core is made up of heavier elements than the mantle. (C)</p> Signup and view all the answers

    What is the primary evidence for the liquid nature of the Earth's outer core?

    <p>The absence of S-waves in the outer core. (A)</p> Signup and view all the answers

    How does the Earth's magnetic field originate?

    <p>The rotation of the liquid outer core. (B)</p> Signup and view all the answers

    What is the primary source of heat that drives the convection in the Earth's mantle?

    <p>The heat from the Earth's core. (B)</p> Signup and view all the answers

    Flashcards

    State of Matter

    A classification indicating whether a substance is solid, liquid, or gas.

    Viscosity

    A measure of a fluid's resistance to flow.

    Geotherm

    A curve that illustrates the temperature gradient in Earth's interior.

    Lithosphere

    The rigid outer layer of the Earth, including the upper mantle and crust.

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    Low Velocity Zone (LVZ)

    A region in the upper mantle where seismic waves travel slower, often due to partial melting.

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    S-wave Velocity

    The speed at which shear waves travel through Earth's materials.

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    Partial Melting

    A process that occurs when only a portion of a solid melts, producing magma.

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    Phase Change in Olivine

    Transformation of olivine's crystal structure under high pressure, becoming denser.

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    Olivine Phase Transformation

    Olivine changes to wadsleyite and then to ringwoodite under pressure at 410 km.

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    Seismic Discontinuities

    Major changes in Earth's structure that correlate with phase transformations of minerals.

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    Ringwoodite

    A phase of olivine that forms under extreme pressure, found in meteorites and rare rocks.

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    Heat Flow Budget

    Total heat flow from Earth's interior is approximately 47 x 10^12 Watts.

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    Conduction vs. Convection

    Conduction is heat transfer through solid, while convection involves moving fluids.

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    Radiogenic Heat

    Heat produced by the radioactive decay of elements in the Earth's crust and mantle.

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    Primordial Heat

    Residual heat from Earth's formation, including heat from collision events.

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    Advection

    The bulk movement of heat, such as in volcanic processes.

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    Core/Mantle boundary

    The boundary at approximately 2890 km depth, where solid silicate rock transitions to liquid iron.

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    P-wave

    Primary waves that compress and expand the material they travel through, fastest seismic waves.

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    S-wave

    Secondary waves that shear material, cannot travel through liquids, slower than P-waves.

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    Geothermal gradient

    The rate at which temperature increases with depth in Earth's interior.

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    Density contrast at core/mantle

    An increase in density of about 4 kg/m³ at the core/mantle boundary due to material differences.

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    Earth's inner core

    The solid center of the Earth primarily made of iron and nickel, very hot and under immense pressure.

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    Earth's outer core

    The liquid layer surrounding the inner core, composed mainly of iron and nickel.

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    Seismic wave speeds

    The speed of seismic waves increases with the density of the rock they travel through.

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    Study Notes

    Earth's Interior

    • Earth's interior is layered, with distinct compositional and structural zones.
    • The layers include the crust, mantle, outer core, and inner core.

    Assessment Tools

    • Midterm test: 20%
    • Quizzes (2): 5% each, total 10%
    • Exercises: 30%
    • Project: 20%
    • Labs: 10%
    • Final exam: 40%

    10-20 Billion Years Accumulation of Energy and Matter

    • Stars form from dense clouds of hydrogen molecules in Giant Molecular Clouds
    • Matter coalesces within stars into smaller, denser clumps, which rotate, collapse, and form.
    • Giant Molecular Clouds have densities of 100-1000 particles per cubic centimeter.
    • Sand has a density of 188 particles per cubic centimeter.

    Earth's Interior II

    • Prenominal Heat:
      • Accretion of cm-sized particles creating heat.
      • Physical collisions on a km scale generating significant heat.
      • Gravitational accretion on a 10-100 km scale producing enormous heat.
      • Molten protoplanet formation from initial heat of accretion.
    • Heat Transport Mechanisms:
      • Conduction, which is the transfer of heat through direct contact between objects.
      • Convection, which is the transfer of heat through the movement of fluids (liquids or gases).
      • Radiation, which is the transfer of heat through electromagnetic waves.
      • Convection is the dominant heat transfer mechanism in Earth's interior.

    Earth's Interior - P-waves and S-waves Shadow Zones

    • P-waves cannot reach the surface within the shadow zone due to refraction when entering and leaving the core.
    • S-waves cannot travel through the liquid outer core, so they never emerge beyond 105° from the focus.

    Earth's Interior - Layering and Composition of Earth's Interior

    • Measuring the travel times of P and S waves from earthquakes models how wave speeds change with depth. The denser the rock, the faster the waves.
    • Lower Mantle: Gradual increase of S-waves toward depth; no more phase transformations.
    • Core-Mantle Boundary: At ~2890km depth with a sharp change in properties, from solid silicate rock to liquid iron.
    • S-wave velocity drops to zero and P-wave velocity drops from ~13km/s to 8km/s at this boundary.
    • Density increases at the boundary leading to no mixing.
    • Mantle and Core: Temperatures increase at the base of the mantle (~1000°C). There is a source for mantle plumes generating hot spots.

    Earth's Interior - Temperatures Inside Earth

    • Geothermal Gradient: An increase in temperature with depth in Earth's interior.
    • State of Matter (solid/molten): Temperature and pressure determine the state of matter.
    • Viscosity: Resistance to flow is determined by temperature and pressure.
    • Atomic Packing (crystals): How atoms are packed in crystals is determined by temperature and pressure.

    Earth's Interior - Mantle

    • The upper mantle extends from the Moho to 660 km depth.
    • The mantle is relatively cold beneath the Moho.
    • This part of the mantle belongs to the lithosphere.
    • At the base of the lithosphere, S-wave velocity decreases.
    • The low-velocity zone is due to partial melting of olivine and pyroxene.
    • This melt origination of basaltic magma.

    Earth's Interior - Mantle - Phase Transformations

    • Phase change in olivine: The ordinary crystal structure is transformed into a denser, more closely packed structure at high pressure.
    • The first jump at ~410 km depth, with olivine transforming to wadsleyite and ringwoodite.
    • A second jump at ~660 km, where spinel-olivine changes to perovskite-olivine.

    Earth's Interior - Heat Flow Budget

    • Total heat flow from Earth's interior: ~47 x 10^12 Watts (or ~91.6 mW/m2).
    • Conduction and Convection: explained earlier.
    • Advection: bulk movement of heat, like in volcanoes.
    • Heat flow distribution through the crust, upper mantle, lower mantle and core.
    • Crust (24%): upper mantle (22%): Lower mantle (32%): Outer core (22%)

    Earth's Interior - Two Convection Cells

    • Two convection cells exist: One in the mantle and another in the outer core.

    Earth's Interior - Sources of Earth's Heat

    • Radiogenic Heat: Radioactive decay of isotopes (uranium-238, thorium-232, and potassium-40) in the crust and mantle (~50% of heat flow).
    • Primordial Heat: Residual heat from Earth's formation (accretional heat from colliding planetesimals and heat from core and mantle differentiation).
    • Core Heat: Generated by the solidification of the inner core and latent heat release during crystallization.
    • Tidal Heating: Gravitational interactions with the Moon and the Sun (minor contribution).

    Earth's Interior - Plate Tectonics History

    • Evidence of continental drift (1880s-1930s) from fossils, geologic formations, and other data.
    • Supercontinents: Such as Rodinia, Pannotia, Gondwana, and Pangaea.

    Earth's Interior - Sea Floor Age and Paleomagnetism

    • Distribution of seafloor sediments (including pelagic, semi-pelagic, turbidites, and contourites) reveal patterns associated with plate tectonics.
    • Age of seafloor and paleomagnetism (magnetic reversal patterns) exhibit a pattern related to plate spreading at mid-ocean ridges.
    • High rate of deep-water sedimentation rates are between 3 and 60 m per million years.

    Earth's Interior - Sea Floor Sediments

    • Distribution of sediments (red clay, siliceous materials) relate to plate tectonics and oceanographic processes.

    Earth's Interior - Hydrothermal Veins

    • Veins are deposited along fractures in basalt, often associated with divergent and convergent margins.
    • Ores may be transported through plate movement or deposition from fluids expelled from Earth.

    Earth's Interior - Isostasy

    • Isostasy involves the gravitational equilibrium between the lithosphere and asthenosphere.
    • Isostasy is related to the variation in elevation above sea level between continental and oceanic crust.
    • Thickness variation in the lithosphere and isostasy relationships.

    Earth's Interior - Coarse-grained Texture, Rhyolite, Basalt, Gabbro

    • Descriptions and types of igneous rocks.

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    Description

    Explore the fascinating layers of Earth's interior, including the crust, mantle, outer core, and inner core. This quiz covers the formation of stars from Giant Molecular Clouds and the energy accumulation over billions of years. Test your knowledge on these geological and astronomical concepts.

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