Summary: Nebular Hypothesis

Earth: the home planetEarth: the home planet

Earth’s InteriorEarth’s Interior

Earth’s Layered StructureEarth’s Layered Structure

Earth’s interior consists of layersEarth’s interior consists of layers Layers are arranged according to densityLayers are arranged according to density Most dense material is at the center – coreMost dense material is at the center – core Density decreases outwardDensity decreases outward Density layering includes the hydrosphere Density layering includes the hydrosphere

(oceans) and atmosphere(oceans) and atmosphere

Thickness and Composition of Thickness and Composition of Earth’s LayersEarth’s Layers

Earth’s Temperature StructureEarth’s Temperature Structure

How Do We Know?How Do We Know?

Refraction of Seismic WavesRefraction of Seismic Waves

Seismic WavesSeismic Waves

Refraction – change in speed and direction Refraction – change in speed and direction when passing through a material of when passing through a material of different density.different density.

Other EvidenceOther Evidence

Refraction of seismic wavesRefraction of seismic waves Density of the entire planetDensity of the entire planet Gravity (mass) of entire planetGravity (mass) of entire planet Composition of meteoritesComposition of meteorites Existence of magnetic fieldExistence of magnetic field

Earth’s Magnetic DynamoEarth’s Magnetic Dynamo

Earth’s Magnetic FieldEarth’s Magnetic Field

Was it always this way?Was it always this way?

Accretion of the protoplanetAccretion of the protoplanet Homogeneous structureHomogeneous structure Density differentiationDensity differentiation

Density DifferentiationDensity Differentiation

Gravitational effects vary with density of Gravitational effects vary with density of materialmaterial

Materials must be free to moveMaterials must be free to move Requires plastic flow or fluid flowRequires plastic flow or fluid flow Requires heatRequires heat

Earth: The Unfinished PlanetEarth: The Unfinished Planet

Earth continues to lose heatEarth continues to lose heat Volcanism brings material to Earth’s Volcanism brings material to Earth’s

surfacesurface Other processes (subduction) return more Other processes (subduction) return more

dense material to interiordense material to interior Conclusion: Conclusion:

Earth is still under construction!Earth is still under construction!

Implications of anImplications of anUnfinished PlanetUnfinished Planet

VolcanismVolcanism EarthquakesEarthquakes Atmospheric and climate changeAtmospheric and climate change Effects on lifeEffects on life

Theory of Plate TectonicsTheory of Plate Tectonics

Earth’s lithosphere (crust +uppermost Earth’s lithosphere (crust +uppermost mantle) is divided into platesmantle) is divided into plates

Plates move as a result of heat inside the Plates move as a result of heat inside the EarthEarth

Plates interact to cause:Plates interact to cause:– EarthquakesEarthquakes– VolcanosVolcanos– Mountain systemsMountain systems

What makes the plates move?What makes the plates move?

Uneven distribution of heat in the upper Uneven distribution of heat in the upper mantle (mantle (AsthenosphereAsthenosphere) causes heat to rise ) causes heat to rise in some placesin some places

Differences in density cause colder, more Differences in density cause colder, more dense dense LithosphereLithosphere to sink back into the to sink back into the asthenosphereasthenosphere

This This ConvectionConvection drives the motion of the drives the motion of the platesplates

Interactions between Plates Interactions between Plates cause:cause:

EarthquakesEarthquakes VolcanosVolcanos Formation of mountainsFormation of mountains Formation of ocean basinsFormation of ocean basins Increase amount of continental lithosphereIncrease amount of continental lithosphere