Lectire3-PPT---The-Earth-2_1672977650.pdf

Okkk

1. INTERIOR OF
THE EARTH

2. Different Spheres
of the Earth

3. Different Spheres of the Earth
There are
five main
systems or
spheres,
on Earth.
Geosphere: consists of interior and surface of Earth, both of
which are made up of rocks.
Solid outer part of the earth is called lithosphere.
Biosphere: Limited part of earth that can support living things
is referred to as biosphere.
Hydropshere: Third system are areas of Earth that are covered with enormous amounts of water, called
hydrosphere.
Atmosphere: Envelope of gas that keeps planet warm and
provides oxygen for breathing and carbon dioxide
for photosynthesis.
Cryosphere: Contains huge quantities of ice at poles and
elsewhere
•All five of these enormous and complex systems interact with one another to
maintain Earth

4. The Earth’s
Interior

5. The Earth’s Interior
Importance of Studying Earth’s Interior
•Interior is essential to have a holistic understanding of geographic system of
earth.
Importance of earth’s interior is as follows:
•Helps understand physical features on earth
•Helps understand evolution of life.
•In 19th century, scientists put forward geological time scale based on fossils found in rock strata.
•Helps us explore and extract minerals and energy
•Helps us understand how and why Earth’s climate has changed in past
•Helps study and understand other planets in solar system and distant stars
•For example, just like earth, other rocky planets like Mercury, Venus and Mars are made of rock.
•Common minerals like feldspars and metals like aluminium.
•Helps understand earth’s magnetic field.

6. The Earth’s Interior
Sources of Information of the Interior
•Earth’s radius is 6,370 km.
•No one can reach centre of earth and make observations or collect samples of
material.
Physical proof like rocks, magma from volcanos, etc.
Direct Sources
Earth’s interior are classified into two:
Direct Sources
Indirect Sources

7. The Earth’s Interior
1. Mining and Drilling: Deep earth mining and drilling reveal nature of rocks deep
down surface.
Information
known:
Helps deduce that pressure and temperature increase from surface
towards interior deeper depth.
Deduce that density of material increases from top surface to interior bottom.
How are these derived?
•Sources are derived from mining, drilling, and studying vulcanism, and faults in crust.

8. The Earth’s Interior
Important
Projects:
“Deep Ocean Drilling Project” (1968) and “Integrated Ocean
Drilling Project” (2003).
Significance of the projects:
Changes in Earth’s magnetic field,
Structure of oceanic crust and upper mantle.
Processes that generate major earthquakes and tsunamis.
Earth’s climate history
Limitations of Mining and
Drilling:
Beyond a certain point, mining and drilling becomes impossible

9. The Earth’s Interior
2. Vulcanism: After a volcanic eruption, lava comes out and cools down
to form different volcanic roks.
Rocks provide us with information about different minerals present in earth's interior, temperature
conditions etc.
3.Surface Rocks:
Helps understanding form of material that can be found up
to a certain depth

10. The Earth’s Interior
Meteorites: Since all space matter had a common beginning, meteorites help
understand earth's materials composition.
For example: Iron meteorites help us understand why find iron in
earth’s interior.
Earth’s
gravitational
field:
Gravitational anomalies help us determine distribution of different
materials within earth.
Earth’s
magnetic field:
Help in understanding presence and distribution of magnetic
materials inside earth.
Provide information about core source of magnetic field.
Seismic Knowledge:
Scientists have applied knowledge of how seismic waves interact with different materials to understand earth's internal structure.
Indirect Sources

11. The Earth’s Interior
Gravitational
force:
•Force that attracts any two objects with mass.
•Greater material mass, stronger gravitational pull.
Gravitational
anomaly:
•Uneven distribution of mass in different materials greatly
influences gravitational force.
•For example, granite is dense and has a high mass.
•Higher gravitational pull than a less dense material of same
volume, such as water.
•Variation in gravity is known as gravitational anomaly.

12. Seismic
Waves

13. Seismic Waves
Earthquake occurs shockwaves of energy, called seismic waves, released from
earthquake focus.
Waves travel through different materials at different speeds.
Waves are recorded and measured by an instrument called
seismometer.
Seismometer produces a graph called a seismogram , shows these waves.

14. Seismic Waves
Outer Core is Liquid:
•Based on absence of S waves
beyond 105° and slowing of P
waves, scientists concluded that
outer core is liquid.
Inner Core is Solid:
•Beyond 145 degrees, P waves again emerged.
•Speed of P wave also increased.
•Helped scientists conclude that inner core is solid.
Significance of the Observations:

15. Seismic Waves
Movement through
different materials
They can move
through solid, liquid
and gaseous
substances of the
earth’s interior.
It can move only
through solid
substances.
It can move only
through solid
materials.
Speed It has the highest
speed-about 5 to
14 km per second.
The speed is lower
than ‘P’ wave-3.5-
7.2 km per second.
It moves slower than
‘P’ and ‘S’ waves-
about 3 to 5 km per
second.

16. Structure of the
Earth

17. Structure of the Earth
Scientists have divided earth into concentric layers based on data collected from
seismic studies.
Three main layers -
Very thin and brittle
outer shell called crust,
middle shell named
mantle and inner core.
Core accounts for almost half of Earth’s radius, but amounts
to only 16.1% of Earth’s volume.
Most of Earth’s volume (82.5%) is its mantle and only a small fraction (1.4%) is its crust.

18. Structure of the Earth
Crust
•Uppermost and thinnest layer of Earth.
•Broad mixture of different types of rocks like igneous, metamorphic, and
sedimentary rocks.
•Granitic and forms continental landmasses.
•Primarily composed of silica and alumina and called “sial.
Upper Crust:
•Continuous zone of dense basaltic rocks that forms ocean floors.
•Mainly composed of silica and magnesium; hence commonly referred to as “sima.”
Lower Crust:
Divisions of Crust:

19. Structure of the Earth
•Continental crust or the “Sial” is lower in density (2.7g/cm³) as
compared to oceanic crust or the “Sima”( 3.5g/cm³ ).
•Continental crust floats higher in mantle than ocean crust because of
lower density of continental crust.
Density:
•Average thickness of crust below ocean is 5 km, whereas continent is around 30 km.
Thickness:
•Transition between sial and sima is called Conrad discontinuity.
Seismic Discontinuity:

20. Structure of the Earth
Mantle
Extent:
•Mantle extends from Moho’s discontinuity to a depth of 2,900 km.
Density:
•Density of mantle is about 4.5 g/cm3.
Composition:
•Mantle comprises minerals like pyroxene, olivine, garnet, plagioclase, and
amphibolite.
It lies between Earth’s crust and core.

21. Structure of the Earth
Upper Mantle: Depth: Ranges from 403 to 660 km from the crust.
Temperature: Ranges from 500 to 900 degrees Celsius.
Upper mantle is more viscous than lower mantle as there is less
pressure than lower mantle.
Lower Mantle: Depth: Around 660 to 2,891 km.
Temperature: Lower mantle is much hotter, reaching 4,000
degrees Celsius.
Seismic Discontinuity: Repetti discontinuity separates upper and
lower mantle.
Divisions of the Mantle:

22. Structure of the Earth
Asthenosphere:
•Upper mantle contains a weaker zone called asthenosphere.
•Extends up to 400 to 500 km from surface.
•Primary source of magma that flows out to surface during volcanic eruptions.
Lithosphere:
•Crust and uppermost part of mantle above Asthenosphere are collectively called
Lithosphere.

23. Structure of the Earth

24. Structure of the Earth
Core:
•Extent:Zone extends from 2900km to approximately 6371km.
•Seismic Discontinuity:Gutenberg discontinuity determines mantle-core
boundary at a depth of 2900km.
•Composition:Core comprises heaviest materials like nickel and iron and called
“Nife”.

25. Structure of the Earth
Outer Core:
•Thickness:About 2,200km thick.
•Temperature: Ranges between
4,500° and 5,500 degrees Celsius.
•Density: Between 12.6-13 g/cm3.
•Outer core is presumed to be
liquid based on studies of seismic
waves.
•Significance:Outer core is
primarily responsible for Earth’s
magnetic field.
Inner Core:
•Composition:Mainly composed of
iron.
•Temperature: About 5,200°
Celsius.
•Inner core is assessed as solid.
•Density:Between 9.9-12.2 g/cm3
•Seismic Discontinuity:Lehmann
discontinuity separates outer and inner core.
Division of Core:

26. Temperature, Pressure
and Density of Earth’s
Interior

27. Temperature, Pressure and Density of Earth’s Interior
Temperature:
•Rise in temperature with increasing depth.
•Rate of increase is not uniform.
•Temperature is around 1000° C at base of crust.
•Rises to around 3500° C at base of mantle and around 5,000°C at Earth’s centre.

28. Temperature, Pressure and Density of Earth’s Interior
•Change in earth’s temperature with depth is called geothermal
gradient.
Geothermal Gradient:
•Frictional heat leftover from collisions of large and small particles that
created Earth
•Decay of radioactive materials present within earth through process of
radioactivity.
•Process includes disintegration of natural radioactive elements inside
earth.
Sources of Heat:

29. Temperature, Pressure and Density of Earth’s Interior
•Pressure is due to huge weight of overlying rocks.
•Pressure increases with increasing depth.
•Pressure at centre of the earth is 364 Gpa.
Pressure:
•Density also increases with increasing depth.
•Density of core ranges between 9.5-14.5g/cm3.
Density:

30. Earth’s Magnetic
Field

31. Earth’s Magnetic Field
•Liquid outer core is major source of earth’s magnetic field.
•Contains metallic minerals like iron and nickel.
Source of Earth’s Magnetic Field:
•Driven by earth’s rotation and convective forces, metallic minerals are
continuously moved within core, generating huge electric currents.
•Process is called geodynamo.
•Responsible for creating and maintaining earth’s magnetic field.
Geodynamo:

32. Earth’s Magnetic Field
•Earth has two sets of poles, geographic pole and magnetic poles.
•Earth's magnetic field can be visualized if one imagines a large bar
magnet inside our planet, roughly aligned with Earth's axis.
•Each end of magnet lies relatively close to geographic North and South
poles.
•Interestingly, magnetic field does not align with earth’s axis of rotation.
•Result, compass needle points towards magnetic north pole and not
geographic north .
Magnetic Poles:
•Angle between true North and magnetic North at any particular position on Earth is called the declination angle.
Declination Angle:

33. Earth’s Magnetic Field

34. Earth’s Magnetic Field
Polar Reversal:
•Complete reversal of magnetic poles of earth over several thousands of years.
•Means that north pole takes up position of south pole and vice versa.
•Cause:Reversal has been attributed to changes in convection pattern in Earth’s
core.
Magnetosphere:
•Region above ionosphere that is defined by extent of Earth’s magnetic field in
space.

35. Earth’s Magnetic Field
Magnetopause:
Abrupt boundary between a magnetosphere and the surrounding
solar wind plasma.
Magnetosheath:
Turbulent magnetic region just outside magnetopause.
Bow Shock:
Located sunward of magnetopause ; solar wind slows abruptly.
Plasmasphere: Located inside magnetosphere
Region containing low-energy charged particles.
Region begins at height of 60 km, extends up to 3 or 4 Earth radii, and includes ionosphere.
Region rotates with Earth.

36. Earth’s Magnetic Field
Significance of the
Magnetosphere:
Protects Earth from charged particles of solar wind and cosmic
rays that would otherwise strip away upper atmosphere,
including ozone layer.

37. Van Allen
Radiation Belt

38. THANK YOU