The Earth: A Vibrant Planet

Sorry to break it to you but the earth is NOT round – rather a spheroid. It bulges at the equator and flattens at the poles…

Structure of the Earth

Earth: From Core to Crust

CRUST – earth’s exposed rockMOHO the separation between the crust and the asthenosphereASTHENOSPHERE – Plastic like substance – responsible for movement of earth’s crust.MANTLE (MESOSPHERE) a semi-liquid plastic consistency which liquefies when pressure is reducedOUTER CORE liquidINNER CORE solid

THE STRUCTURE OF THE EARTH:

Heating of the Earth causes convection currents in the Mantle

This in turn causes stress on the surface of the earth…

We know the structure of the earth due to the study of SEISMOLOGY (the study

of earthquake waves)

• the branch of geology that studies earthquakes•Primary (P) waves and Secondary (S) waves pass through the internal layers of the planet

Primary Waves

• P waves stretch and squeeze; moving quickly, can pass through any material

• Travel by compression through solids, liquids, and gases

• Speed up through the mantle

• Drop at the outer core (liquid)

• Speed up at the inner core (solid)

Secondary Waves• S waves vibrate passing only through

solids

• Slower than the P wave (60% of the speed)

• Will NOT travel through liquid

• Speeds up gradually through the mantle

• Then stops at outer core

Waves in Action

The use of “indirect evidence” serves to tell us the structure of the earth. Refraction and Shadow zones and arrival times are crucial

Our Vibrant Earth

A Sombrio Production