The document discusses what lies within Earth's interior based on indirect evidence from seismic waves. [1] Seismic waves provide information about Earth's layered structure as the waves refract and reflect differently depending on density changes. [2] Earth has a crust, mantle, outer core, and inner core, with increasing temperatures and pressures toward the center. [3] The core generates Earth's magnetic field through its spinning liquid outer layer.

8. But the question still remains
WHAT LIES IN EARTH’S INTERIOR?

10. Question of density
• The average relative density of Earth comes
out to be 5.5.
• Surprisingly enough.. All the rocks found on
Earth’s surface have a density between 3- 3.5 .

11. Earth’s Magnetic Field

12. Temperature and Volcanism
• Magma coming out of volcanoes.
• Experiences of people engaged in mining
activities.

13. How do we know about Earth’s
interior?
• Through INDIRECT EVIDENCE, mostly from
seismic waves caused by earthquakes.
• As we have no technology to go inside the
earth ,indirect evidence is the only option for
scientists to develop a theory.

14. Seismic waves : What are they?
• Seismic waves are waves of energy that travel
through the earth, and are a result of an
earthquake, explosion, or a volcano that
imparts low-frequency acoustic energy.

15. Seismic waves
• P waves - Primary waves
• S waves - Secondary waves
• L waves – Lateral waves

19. Phenomena associated
Reflection Refraction

21. As Seismic waves behave like light
waves..
• They refract and reflect • We record this on the
at different boundaries surface and observe the
and zones and move at changes and thus
different speeds in the interpret them. Lets
same period of time. have a look how?

24. Different layers of
THE EARTH

25. The Four
• The Earth is composed of
Layers four different layers. The
crust is the layer that you
live on, and it is the most
Crust widely studied and
Mantle
understood. The mantle
is much hotter and has the
Outer Core ability to flow. The outer
core and inner core are
even hotter with pressures
Inner Core so great you would be
squeezed into a ball
smaller than a marble if
you were able to go to the
center of the Earth!

27. Crust
• The crust, the outermost layer, is rigid and
very thin
• Oceanic Crust (beneath the ocean) is about 5
km thick
• Continental Crust (under land) averages about
30 km and 100 km deep.
• Like the shell of a hardboiled egg

29. Mantle
• The Mantle is a dense, hot layer of semi-solid
rock approximately 2,900 km thick.
• The mantle contains more
iron, magnesium, and calcium than the crust
• is hotter and denser because temperature and
pressure inside the Earth increase with depth.
• As a comparison, the mantle might be thought
of as the white of a boiled egg.

31. Core
• the core, is nearly twice as dense as the mantle
because its composition is metallic (iron-nickel alloy).
• the Earth's core is made up of two distinct parts:
– a 2,200 km-thick liquid outer core
– a 1,250 km-thick solid inner core
– As the Earth rotates, the liquid outer core spins, creating
the Earth's magnetic field.

36. The core is important as..
• It is thought to be the main reason behind the
driving forces of convective currents in
Mantle.
• It is responsible to maintain Earth’s magnetic
field.

38. If the core stops spinning, the magnetic field will collapse resulting in
destruction of Earth’s surface by violent solar storms.