U2L3: Inside the Earth
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What are the key characteristics of Primary (P) waves?
Fastest seismic waves; travel through solids and liquids; cause back-and-forth compression motion
What are the key characteristics of Secondary (S) waves?
Slower than P waves; only travel through solids; move rock perpendicular to wave direction; cannot pass through the liquid outer core
What is refraction?
The bending of waves as they move between materials of different densities
What does refraction help scientists do?
Determine the densities and boundaries of Earth’s layers
What is the crust like?
Solid thin outermost layer
What is the mantle like?
Mostly solid; thickest layer; rock moves like putty over long time scales
What is the outer core like?
Liquid layer made of molten iron and nickel
What is the inner core like?
Solid layer of iron and nickel due to high pressure
What is the lithosphere?
Rigid outer layer including the crust and uppermost mantle
What is the asthenosphere?
Soft weak plastic-like layer under the lithosphere
What is the mesosphere?
Strong lower part of the mantle
How do scientists obtain mantle samples?
Volcanic eruptions bring up mantle rock called xenoliths
What are the two main sources of heat inside Earth?
Radioactive decay and leftover heat from Earth’s formation
What are convection currents?
Movement where warm less-dense material rises and cool denser material sinks
Why are convection currents important?
They drive plate tectonics
What is differentiation?
Process where Earth separated into layers based on density
Which materials formed Earth’s core?
Dense materials like iron and nickel
Which materials formed Earth’s crust?
Least dense silica-rich materials
How is Earth’s differentiation similar to solar system formation?
In both gravity pulled the densest materials toward the center