Density and Mantle Convection Blue Type: Read, listen, and think Black Type: Take notes.

Density and Mantle Convection

Blue Type: Read, listen, and thinkBlack Type: Take notes

A shock wave is high density air

Density = Mass / Volume

A greater density means more mass in a given volume.

Similar to population densityPopulation density = Number of people / sq. mi.

Why does smoke rise?

Smoke is less dense than surrounding air. Air is pulled down by gravity and pushes the smoke up.

Test your understanding

You break a brick in half. How does the density of ½ brick compare to the density of the whole brick?

A) Density is half as great.B) Density stays the same.C) Density doubles.D) Impossible to tell.

What is convection?Convection: The transfer of heat energy by the movement of matter.

Less dense matter rises

More dense matter falls

Convection Current Demo

What is needed for convection?

• Matter that flows: gas, liquid, “plastic”– “Plastic” = a solid that can flow – Silly putty

• Density that changes as temperature changes• Room to flow • A gravitational difference (so denser material

sinks and pushes less dense material up)

Earth’s Interior is HOT!

Earth’s mantle brings heat to the surface by convection. It is released where crust spreads apart.

The plates move a few cm per year on average.

Convection Currents in the Mantle

Why do we care?

Tsunami, earthquake and volcano predictions depend on knowing about Earth’s interior.

Test your understanding

Why does fiberglass insulation in your attic help your house stay warm?

A) It produces heat to keep the attic warm.B) It reduces air movement.C) It increases convection.D) It absorbs radiation from the sun.