HMH Science Dimensions: Plate Tectonics Lesson 1 Quiz

Earth's Crust and Composition

• Average thickness of Earth's continental crust is approximately 30-50 kilometers.
• The continental crust is thickest in mountain ranges, such as the Himalayas.

Earth's Core and Boreholes

• Scientists have not collected samples from Earth’s core due to extreme temperatures and pressures.
• The deepest borehole on Earth, the Kola Superdeep Borehole, is located in northwestern Russia.

Earth's Layers

• The outermost compositional layer of Earth is the crust.
• The mantle is denser than the crust due to increased pressure and temperature as depth increases.

Seismic Activity and Evidence

• Seismic waves are caused by the sudden release of energy in the Earth's interior, often due to tectonic movements.
• Properties of the asthenosphere are inferred from seismic data, which provides information about wave speeds and behavior as they travel through different layers.

Wave Velocity and Insights

• A graph showing the velocity of P- and S-waves with depth in Earth’s mantle reveals changes in material properties and states (solid/liquid).
• Gradual changes in seismic wave velocity with depth indicate transitions between layers with different densities and states of matter.

Additional Geophysical Phenomena

• The aurora borealis occurs near the poles due to interactions between solar wind particles and Earth’s magnetic field.
• Flow of solid rock in the mantle is driven by heat from the Earth's inner layers, creating convection currents.

Meteorites and Internal Layers

• Many stony meteorites resemble rocks found in Earth's crust due to similar mineral compositions.
• Seismic waves help reveal the internal structure of Earth, showing variations in layers based on wave behavior and velocity changes.