Earth: the home planet

Earth’s Interior

Earth’s Layered Structure Earth’s interior consists of layers Earth’s interior consists of layers Layers are arranged according to density Layers are arranged according to density Most dense material is at the center – core Most dense material is at the center – core Density decreases outward Density decreases outward Density layering includes the hydrosphere (oceans) and atmosphere Density layering includes the hydrosphere (oceans) and atmosphere

Thickness and Composition of Earth’s Layers

Earth’s Temperature Structure

How Do We Know?

Refraction of Seismic Waves

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

Other Evidence Refraction of seismic waves Refraction of seismic waves Density of the entire planet Density of the entire planet Gravity (mass) of entire planet Gravity (mass) of entire planet Composition of meteorites Composition of meteorites Existence of magnetic field Existence of magnetic field

Earth’s Magnetic Dynamo

Earth’s Magnetic Field

Was it always this way? Accretion of the protoplanet Accretion of the protoplanet Homogeneous structure Homogeneous structure Density differentiation Density differentiation

Density Differentiation Gravitational effects vary with density of material Gravitational effects vary with density of material Materials must be free to move Materials must be free to move Requires plastic flow or fluid flow Requires plastic flow or fluid flow Requires heat Requires heat

Earth: The Unfinished Planet Earth continues to lose heat Earth continues to lose heat Volcanism brings material to Earth’s surface Volcanism brings material to Earth’s surface Other processes (subduction) return more dense material to interior Other processes (subduction) return more dense material to interior Conclusion: Earth is still under construction! Conclusion: Earth is still under construction!

Implications of an Unfinished Planet Volcanism Volcanism Earthquakes Earthquakes Atmospheric and climate change Atmospheric and climate change Effects on life Effects on life

Theory of Plate Tectonics Earth’s lithosphere (crust +uppermost mantle) is divided into plates Earth’s lithosphere (crust +uppermost mantle) is divided into plates Plates move as a result of heat inside the Earth Plates move as a result of heat inside the Earth Plates interact to cause: Plates interact to cause: –Earthquakes –Volcanos –Mountain systems

What makes the plates move? Uneven distribution of heat in the upper mantle (Asthenosphere) causes heat to rise in some places Uneven distribution of heat in the upper mantle (Asthenosphere) causes heat to rise in some places Differences in density cause colder, more dense Lithosphere to sink back into the asthenosphere Differences in density cause colder, more dense Lithosphere to sink back into the asthenosphere This Convection drives the motion of the plates This Convection drives the motion of the plates

Interactions between Plates cause: Earthquakes Earthquakes Volcanos Volcanos Formation of mountains Formation of mountains Formation of ocean basins Formation of ocean basins Increase amount of continental lithosphere Increase amount of continental lithosphere