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Page 1: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Convection in the Mantle

Page 2: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Keyterms

• DensityDensity-mass/volume. The amount of matter in a given area or volume of that matter.

• FluidFluid-matter that can flow. Can be solids, liquids, or gasses

• ConvectionConvection-heat transfer within a fluid. • Convection currentConvection current -a current that develops from a

fluid moving from an area of high density to an area of low density.

Page 3: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

How do convection currents form?

• Convection currents occur when fluids heat

unevenly and areas develop that are different in density

Page 4: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

What are examples of convection currents?

Page 5: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Lava Lamps (see demo)

Page 6: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Boiling water

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Ocean Currents

Page 8: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Air currents in clouds

Page 9: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

The Mantle

Page 10: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that
Page 11: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

What is the theory of plate tectonics?

• The theory of plate tectonics explains the formation and movement of Earth’s plates.• The lithosphere is broken into

sections called plates.

Page 12: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Plate Boundaries:

• Divergent Boundaries- The place where two plates (pieces of the lithosphere) move apart.

• Most divergent boundaries occur along a mid-ocean ridge where sea-floor spreading occurs.

Page 13: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

What is a mid-ocean ridge?

• It is an undersea mountain chain where new ocean floor is produced at a divergent boundary.

Page 14: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Convergent Boundaries:• The place where two plates come together

(often called a collision).• When two plates collide, the density of the

plate determines which one comes out on top.

Page 15: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Convergent Boundaries:• 2 continental plates collide= formation of

mountains• 1 oceanic + 1 continental collide= oceanic

sinks beneath the continental plate (subduction) and forms a trench (a narrow, deep valley along the ocean floor).

• Subduction- the process by which oceanic crust sinks beneath a less dense plate.

Page 16: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Subduction Diagram

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Transform Boundaries:

• A place where two plates slip past each other, moving in opposite directions.

• Earthquakes often occur along transform boundaries, but crust is neither created nor destroyed.

Page 18: Convection in the Mantle. Keyterms Density Density-mass/volume. The amount of matter in a given area or volume of that matter. Fluid Fluid-matter that

Diagram of plate movement:

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Evidence for Plate Tectonics

• Pangaea- The name of the single landmasss that broke apart 200 million years ago and gave shape to today’s continents.

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Evidence for a Supercontinent

• Land features: mountain ranges and coal fields appear to line up according to the shape of continents.

• Fossils: from ancient animals appear to link continents together as well- mesosaurus, lystrosaurus (freshwater reptiles), glossopteris (plant).

• Climate: temperature changes at specific locations show that continents may have shifted toward or away from the equator over time.

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Evidence for Plate Tectonics

• Sea-Floor Spreading- the process by which molten material adds new oceanic crust to the ocean floor.

• The sea floor spreads apart along both sides of a mid-ocean ridge (divergent boundary), as new crust is added.

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Sea-Floor Spreading Diagram

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How do we know the sea-floor actually spreads?

• Evidence from molten material- new material is erupting along mid-ocean ridges.

• Evidence from drilling samples- the age of rocks have been identified through drilling samples. Rocks farther from the ridge were the oldest, the youngest rocks were always in the center of the ridges.


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