The document discusses the internal structure and composition of the Earth. It describes how temperature, pressure, and density increase towards the core. The Earth has a solid inner core made of iron and nickel, a liquid outer core also made of iron and nickel, a thick mantle made of silicate rocks, and a thin crust on top. Seismic data is used to determine this internal structure.

3. Formation: Density Stratification (Layering)

4. Temperature Increases As You Move
Towards the Center of the Earth
• Friction generated during
formation.
• Nuclear decay of
radioactive elements

5. Pressure

6. Density and
Pressure also
Increase as you
move towards
the core.

7. How Do We Know?
Scientists use seismographic (energy waves produced by
earthquakes) data recorded at research stations positioned all
over the world to piece together the earths internal structure.

9. Earth’s Interior
• Core
– High Density
– Iron and Nickel
– Inner Core - solid
– Outer Core - liquid
– Less dense than core
– Iron and Magnesium silicates
– Mostly solid
– Upper mantle is partially molten
• Mantle
– Outermost layer
– Very thin and rigid
– Continental – granite
– Density = 2.8 g/cm3
– Oceanic – basalt
– Density = 3.0 g/cm3
• Crust

10. The Inner Core
 Center of the earth
 Deepest layer, 6250 km under
the surface.
 A solid ball of an iron alloy
(sulphur & nickle traces).
 Solidified due to intense
pressure.
 2400 km in diameter.
 Approximately 6000°C
- Hotter than the surface of the
sun.

11. The Outer Core
• Layer of molten (liquid) Iron
between Inner Core and
Mantle.
• 2,300 km thick.
• Cooler than inner core, but
still scorching hot at 4,500°C
• Mostly iron, plus sulphur &
nickle.
• Constantly in motion as the
earth spins.
– Generates Earth’s
electromagnetic field.

13. The Mantle
• Middle layer (Between Crust and Core)
• 2900 km thick (approx 84% of earth’s volume).
• Temperature:
o 500°C near crust
o 4,000°C near outer core.
• Composed of Magnesium, Iron, Aluminum,
Silicon and Oxygen.

14. Convection Currents
in the Mantle
• The mantle is made of
“solid” rock.
– The rock is extremely hot
but the high pressure
keeps it from melting.
• The rock is “plastic” and
does flow and move
around, like hot asphalt.
– Hot rock rises and cooler
rock descends creating
slow moving convection
currents.

15. Earth’s Crust
• Thin Outermost Layer (0-40km)
– Made up of low density materials.
– Solid Rock (Broken up into large plates)
• Divided into 2 Types:
– Continental Crust:
• Made primarily of Granite.
• Density of 2.7 g/cm3 (less dense)
• Thickness of 40km
• Oldest Crust
– Oceanic Crust:
• Made Primarily of Basalt
• Density of 2.9 g/cm3 (more dense)
• Thickness of 8km
• Youngest Crust
• Bill Nye

16. Layers of the Earth Rap

17. PLATE TECTONICS
Alfred Wegener and the Theory of Continental Drift

19. Alfred Wegner: Continental Drift

22. “The Origin of the Continents
and Oceans” 1906
• Wegner laid out his theory of
plate tectonics and continental
drift.
– Proposed that the continents
were actually large mobile
plates of crust.
– Could not explain the
mechanism by which the
continents move.
• Wegner’s theory was largely
ignored and written off by the
scientific community for nearly
50 years.

23. Plate Tectonics
• The Earth’s crust is divided into 12 major
plates which are moved in various
directions.
• This plate motion causes them to collide,
pull apart, or scrape against each other.
• Each type of interaction causes a
characteristic set of Earth structures or
“tectonic” features.
• The word, tectonic, refers to the
deformation of the crust as a consequence
of plate interaction.

24. World Plates

25. What are tectonic plates made of?
• Plates are made
of rigid
lithosphere.
The lithosphere is made up
of the crust and the upper
part of the mantle.

26. Plate Movement
• “Plates” of lithosphere are moved around by the
underlying hot mantle convection cells

27. • Divergent
• Convergent
• Transform
Three types of plate boundary

28. • Spreading ridges
– As plates move apart new material is erupted to fill the gap
• In plate tectonics, a divergent boundary is a linear feature that
exists between two tectonic plates that are moving away from each
other. These areas can form in the middle of continents or on the
ocean floor.
• As the plates pull apart, hot molten material can rise up this newly
formed pathway to the surface - causing volcanic activity.
Divergent Boundaries

29. Age of Oceanic Crust
Ocean Ridges: This map shows the age of the oceanic crust.
Red: shows the youngest ages.
Blue: shows the oldest ages (around 200 million years old).
New crust is created at divergent plate boundaries

30. • Iceland has a divergent
plate boundary running
through its middle
Iceland: An example of continental rifting

31. • Convergent boundaries are where the plates
move towards each other.
• There are three types of convergent boundary,
each defined by what type of crust (continental
or oceanic) is coming together.
• There are three styles of convergent plate
boundaries
– Continent-continent collision
– Continent-oceanic crust collision
– Ocean-ocean collision
Convergent Boundaries

32. Forms Mountains (Example: European Alps and Himalayas)
Continent-Continent Collision
• When continental crust pushes against continental crust both sides of the
convergent boundary have the same properties.
• Neither side of the boundary wants to sink beneath the other side, and as a
result the two plates push against each other and the crust buckles and
cracks, pushing up (and down into the mantle) high mountain ranges.

33. Himalayas

34. • At a convergent boundary where continental crust pushes against
oceanic crust, the oceanic crust which is thinner and more dense than
the continental crust, sinks below the continental crust.
• This is called a Subduction Zone. The oceanic crust descends into the
mantle at a rate of centimeters per year.
• Subduction is a way of recycling the oceanic crust. Eventually the
subducting slab sinks down into the mantle to be recycled.
• It is for this reason that the oceanic crust is much younger than the
continental crust which is not recycled.
Continent-Oceanic Crust Collision

35. • Oceanic lithosphere subducts
underneath the continental
lithosphere
• Oceanic lithosphere heats and
dehydrates as it subsides
• The melt rises forming
volcanism
• E.g. The Andes
Subduction

36. • When two oceanic plates collide, one runs over the
other which causes it to sink into the mantle forming
a subduction zone.
• The subducting plate is bent downward to form a
very deep depression in the ocean floor called a
trench.
• The worlds deepest parts of the ocean are found
along trenches.
– E.g. The Mariana Trench is 11 km deep!
Ocean-Ocean Plate Collision

38. • Where plates slide past each other.
• Also known as strike-slip faults.
• Frequently form earthquakes.
Transform Boundaries
Above: View of the San Andreas
transform fault

40. Volcanism is
mostly focused at
plate margins
Pacific Ring of Fire

41. - Subduction - Rifting - Hotspots
Volcanoes are formed by:

42. Pacific Ring of Fire
Hotspot
volcanoes

43. • Hot mantle plumes breaching the surface in
the middle of a tectonic plate
What are Hotspot Volcanoes?
Photo: Tom Pfeiffer / www.volcanodiscovery.com
The Hawaiian island chain are examples
of hotspot volcanoes.

44. Hot Spot Volcanoes
The tectonic plate moves over a fixed
hotspot forming a chain of volcanoes.
The volcanoes get younger from one end to the other.

45. As with volcanoes, earthquakes are not randomly
distributed over the globe
At the boundaries between plates, friction causes them
to stick together. When built up energy causes them to
break, earthquakes occur.
Figure showing the
distribution of
earthquakes
around the globe

46. Where do earthquakes form?
Figure showing the tectonic setting of earthquakes

47. Plate Tectonics Summary
• The Earth is made up of 3 main layers (core,
mantle, crust)
• On the surface of the Earth are tectonic plates
that slowly move around the globe
• Plates are made of crust and upper mantle
(lithosphere)
• There are 2 types of plate
• There are 3 types of plate boundaries
• Volcanoes and Earthquakes are closely linked to
the margins of the tectonic plates