Transcript Document

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
THE STRUCTURE OF THE
EARTH:
CRUST – earth’s exposed rock
MOHO the separation between the crust and the
asthenosphere
ASTHENOSPHERE – Plastic like substance –
responsible for movement of earth’s crust.
MANTLE (MESOSPHERE) a semi-liquid plastic
consistency which liquefies when pressure is
reduced
OUTER CORE liquid
INNER CORE solid
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