The document summarizes the structure and composition of Earth's interior layers. It describes how seismic waves and samples from deep drilling provide evidence that the Earth has distinct layers, including a crust, mantle, outer core, and inner core. The crust varies in thickness and composition between continental and oceanic crust. Below the crust lies the mantle, which makes up over 80% of the Earth's volume and is divided into an upper and lower mantle. The lower mantle and outer core are liquid, while the inner core is solid.

1. STRUCTURE AND COMPOSITION OF
THE EARTH’S CRUST

2. DO WE KNOW
WHAT THINGS LIES
BENEATH THE
EARTH SURFACE?
This is our Earth!

3. ORIGIN OF THE EARTH
 Meteors and Asteroids bombarded the Earth.
 Gravitational compression.
 Density Stratified planet.

4. EVIDENCE OF INTERNAL STRUCTURE
 Direct & Indirect
 Direct evidence:
From rock samples. Scientists drill up to 12 km into
the earth. Forces blast rock from as deep as 100 km.
 Indirect evidence:
From seismic waves

5.  Scientists record Seismic waves
 Travel times and direction to give indication of internal structure of Earth.
 Two kind of seismic waves
 P(Primary) wave:
-push and pull movement.
-travel through both solid and liquid material.
-Travel fastest (~ 6 km/sec).
-travel through crust (6km/sec) and mantle (8km/sec).
 S(secondary or shear)waves:
-move side-to-side.
-only travel through solid materials.
-slower(~4km/sec)

6. • The velocity of P-wave depends on how easily
the material can be compressed , rigidity and
density of the material.
• S-waves travel through material by shearing it
or changing its shape in the direction
perpendicular to the direction of travel.

7. Earth interior layers
 The earth has layered interior
Crust
Mantle Upper
lower
Core Inner
Outer

8. THE CRUST
 This is where we live!
 A layer of rock that forms the Earth’s outer skin including the rock under
the ocean
 It is very thin in comparison to the other three layers.
Crust
Continental
Oceanic

9. Continental Crust vs Oceanic Crust
 Continental Crust
-underlines the continent
rock density : 2.7 gm/cmᶟ
Avg. rock thickness: 35-40km
rock type: Granite
-At least 3.8 billion years old
 Oceanic Crust
-underlines the ocean
rock density: 3.7gm/cmᶟ
Avg. rock thickness: 7-10 km
rock type : Basalt
-200 million years old
Continental
oceanic

10. CRUSTAL COMPOSITION

11. THE MANTLE(35–2,890km)
1 • The Mantle is the largest layer of the Earth.
2
• Solid rock layer between the crust and the core.Middle part of
the Earth interior.
3
• Found silicate,iron,oxygen,magnesium
4
• 2885 km thick,the mante is 82% of Earth volume.
5
• Average temperature is 3000°c

12. Mantle
Upper Lower
 Upper mantle is the upper part of the
mantle.
 Lower Mantle is the lower part the
Mantle.

13. THE LITHOSPHERE(0~100KM)
 The crust and the upper layer of the mantle together make up a zone of
rigid, brittle rock called the Lithosphere.
 just above the asthenosphere.

14. THE ASTHENOSPHERE(~100 TO
660KM)
 A Thin zone that lies below the lithosphere.
 Its materials behave like flowing plastic.
 Region of upper mantle.

15. Mesosphere (660 to 2900 km)
 Rock in the lower mantle gradually strengthens with depth, but it is still
capable of flow.
mesosphere

16. MANTLE CONVECTION CELL
 Convection- heat transfer by movement of heated fluids.
 In the mantle hot material rises towards the lithosphere .The
hot material reaches the base of the lithosphere where it
cools and sinks back down through the mantle. The cool
material is replaced by more hot material, and so on forming
a large “convection cell”

17. MANTLE CONVECTION CELL
 As plates move apart new warm material is erupted to fill the gap.

18. THE CORE
 Inner part of the Earth’s interior.
 The core of the Earth is like a ball of very hot metals.
core
Inner
Outer

19. OUTER CORE(2900 to 5170 km)
 Outer core is liquid and composed of the melted metals of molten iron-
nickel.
 Convective flow of this fluid generates much of the Earth’s magnetic field.
 Temperature is around 2000°c
 Thickness 1400 miles

20. INNER CORE(5170 to 6386 km)
 Inner core is solid iron-nickel alloy.
 It is hotter than the outer core.
 High temperatures and pressures.
 Not able to move about like a liquid.
 Temperatures are estimated between 4500-5500°c
 Thickness 1221 km.

21. EARTH’S MAGNETIC FIELD
 The Earth’s magnetic field is generated by the slowly moving liquid part of
the iron core.
 Earth has a North and South magnetic pole.
 It traps many charged particles from the sun which protects us from
harmful solar radiation.

22. MOHO
 The sharp and well defined junction between the mantle and the crust.
 Found roughly 32 km below the continents and about 10 km below the
ocean.
moho

23. THANK YOU