What limits direct observation of Earth's interior?
Volcanic eruptions and drilling reaching only 3% depth.
What does the gravimetric method measure?
The actual value of gravity with gravimeters.
How does the gravimetric method use theoretical gravity?
It compares actual gravity to theoretical gravity expected from altitude and latitude.
What does a positive gravimetric anomaly indicate?
Denser rocks where actual gravity exceeds theoretical gravity.
What does a negative gravimetric anomaly indicate?
Less dense rocks like salt domes where theoretical gravity exceeds actual gravity.
What type of wave are P waves and through which media do they propagate?
P waves are longitudinal and propagate through solids, liquids, and gases.
How do S waves differ from P waves in propagation and wave type?
S waves are transverse and propagate only through solids.
What defines a seismic discontinuity?
A boundary between layers with different composition or physical state causing abrupt wave speed and direction changes.
How does wave speed change with rigidity and density?
Wave speed increases with rigidity and decreases with density.
What is seismic tomography?
A method creating 3D maps of seismic velocities from many seismic waves at different positions.
How does the geochemical model divide Earth's interior?
Into crust, mantle, and core by chemical composition.
What is the average thickness and density of the continental crust?
50 km thickness and 2.7 g/cm³ density.
What types of rocks does the continental crust contain?
Igneous, metamorphic, and sedimentary rocks.
What is the average thickness and density of the oceanic crust?
9 km thickness and 3.0 g/cm³ density.
What is the age limit of the oceanic crust?
No more than 180 million years old.
What mainly composes the mantle and what separates it from the core?
Iron- and magnesium-rich peridotites; separated by the Gutenberg discontinuity.
Why is the external core liquid and the internal core solid?
High pressure keeps internal core atoms together, making it solid; external core is liquid.
How does the dynamic model divide Earth's interior?
Into lithosphere, asthenosphere, mesosphere, level D, and endosphere.
What layers compose the lithosphere and how thick is it continentally?
Crust plus part of upper mantle; 150–250 km thick continentally.
What is the lithosphere's thickness oceanically?
60–100 km thick oceanically.
What mantle corresponds to the mesosphere in the geochemical model?
The lower mantle.
How does the mesosphere behave under high pressure and temperature?
It behaves like a fluid flowing more slowly than the asthenosphere.
Which authors considered the asthenosphere as the entire sublithospheric upper mantle?
Kearey et al. (2009) and Braun (2010)
To what depth does the most accepted current definition extend the asthenosphere?
To the lower-mantle boundary at 660 km
What does level D produce in Earth's interior?
Thermal plumes, columns of hot material rising toward the surface.
What boundary does deep subduction reach in Earth's interior?
The mesosphere–endosphere boundary.
What happens to material accumulated in level D after deep subduction?
It cools the upper endosphere and produces descending cold currents.
What triggers the rise of material after descending cold currents in level D?
Heating causes the material to rise again.
What causes continental volcanism?
The ascent of hot material.
What causes oceanic volcanism?
Melting of subducting oceanic lithosphere.
Where may oceanic volcanism stop in Earth's interior?
At the asthenosphere–mesosphere boundary.
What is the geothermal gradient?
The increase in temperature as depth increases.
What information does the geothermal gradient provide?
Information about the physical state and chemical composition of rocks.
Why do meteorites inform knowledge of Earth?
They formed from the same material and time as Earth.
Where is the focus or hypocenter located in an earthquake?
Inside Earth where the earthquake originates.
What does low seismic velocity indicate about temperature?
It indicates an increase in temperature.
What does increased seismic velocity in a zone indicate?
It indicates lower temperatures.
How do the upper and lower mantle differ in rigidity and density?
Upper mantle is less rigid with 3.5 g/cm³ density; lower mantle is more rigid with 5.5 g/cm³ density.
What is Level D and what happens to seismic velocities there?
A transition layer between mesosphere and endosphere where seismic velocities decrease considerably.
What characterizes the endosphere's external and internal parts?
External core flows rapidly; internal core flows much more slowly.
Who redefined the asthenosphere as a seismic low-velocity zone in 1926?
Beno Gutenberg
How did Joseph Barrell define the asthenosphere in 1914?
As a mechanically weak sphere needed for isostatic compensation
At what depth did Joseph Barrell place the asthenosphere's detachment level?
100–200 km depth
What did studies by Tackley, Vidal, and Kerr reveal about the asthenosphere?
It is not detected in every region and the whole mantle flows
What causes orogenic volcanism?
Melting of subducting oceanic lithosphere that can reach great depth.
Answer 19 questions on Earth’s Internal Structure and Dynamics.
1. What limits direct investigation of Earth’s interior?
2. How does the gravimetric method identify a gravity anomaly?
Go over the full study guide for Earth’s Internal Structure and Dynamics.
Read the study guide →Upload your class notes and Revizly writes your flashcards in about a minute.
Flashcard maker