1. Section 5-1 Earth’s
Interior

2. Exploring Inside the Earth
Geologists have used two
main types of evidence to
learn about Earth’s
interior:
1. Evidence from
examining rock samples
2. Evidence from seismic
waves
-earthquakes produce
different types of seismic
waves. Some waves can
travel through solids and
liquids others can only
travel through solids.
-Also, they travel at
different speeds as they
move through different
materials.

3. Temperature Inside the Earth
The graph shows how
temperatures change
between Earth’s surface
and the bottom of the
mantle.
Interpreting Data:
How does
temperature change
with depth in Earth’s
interior?
It increases with
depth.

4. Temperature Inside the Earth
•In addition to temperature, pressure
also increases as you go deeper into
the earth, just like a swimming pool!

5. The Crust
•The crust is a layer of solid rock that
includes both dry land and the ocean floor.
•Although continental crust is thicker, it is
less dense.
•Granite is the most common rock on the
continental crust and basalt is the most
common rock on the ocean floor.

6. The Mantle
• Earth’s mantle is made up of rock that is very hot, but
mostly solid. Scientists divide the mantle into layers
based on the physical characteristics of those layers.
1. Lithosphere-upper mantle and crust. Very rigid and solid!
2. Asthenosphere-beneath lithosphere, softest part of the
mantle. It is mostly solid rock but is able to bend and move
like taffy. It does have some areas though which are
melted (molten).
3. Lower Mantle- below asthenosphere. Intense pressure
makes the rock very solid which extends all the way to the
core.

7. The Core
• When the earth was forming, heavy metals
like iron and nickel sank towards the center,
or core. It consists of two parts:
1.Liquid outer core
• The motions of the moving metals and
electrical charges in the outer core are
thought to contribute to the earth’s
magnetic field. When you use a compass,
the needle aligns with the magnetic field.
2. Solid inner core
• Intense pressure squeezes the metals into
a solid.

8. Section 5-2
Convection and
the Mantle

9. Types of Heat Transfer
•You hold an ice cube and your hand
gets cold. Is your hand losing heat or
gaining cold?
•Only heat moves-cold is just the
absence of heat!
•There are three types of heat transfer:
radiation, conduction, and convection.

10. Types of Heat Transfer
1. Radiation is the transfer of energy
through space or air outwards in all
directions from its source.
2. Ex. Sunlight or heat from a fire.

11. Types of Heat Transfer
2. Conduction is the transfer of
energy through touch or contact – like
getting burned on a hot stove.

12. Convection Currents
•3. Convection-Heating and cooling of a fluid
which causes changes in the fluid’s density
and sets convection currents in motion.
•Ex. When you heat water, the water nearest
the stove warms, expands, and becomes less
dense so it moves upward. It then cools,
compacts, and moves downward again.

13. Convection Currents in Earth
•Heat from the core (and the mantle itself)
causes convection currents in the mantle.
•These convection currents ultimately cause
landmasses to move (more on this later)
•What other layer of the Earth has convection
currents?
•The outer core.

14. b

15. Section 5-3
Drifting
Continents

16. Continental Drift
•In 1910, a German scientist named
Alfred Wegener presented his
hypothesis called Continental Drift. It
said that all the continents were once
joined together in a single landmass
called Pangaea and have since moved
through the ocean moving to their
current locations.

17. Evidence for Continental Drift
1. Land Features- The shapes
of the continents matched!

18. Evidence for Continental Drift
2. Climate – As a continent moves toward the
equator, it’s climate becomes warmer. As a
continent moves toward the poles, its climate
becomes colder. But the continent carries with it
the fossils and rocks that formed at its previous
locations.
•Tropical plant fossils have been found on islands
in the arctic ocean!

19. Evidence for Continental Drift
•Striations left behind by glaciers are
found in rocks in areas such as South
Africa and India that now have very
warm climates

20. Evidence for Continental Drift
3. Fossils- Fossils of the Glossopteris plant are
found in Africa, South America, Australia, India and
Antarctica. Mesosaurus fossils are found in both
Africa and South America.
•These places are now separated by oceans!

21. Evidence for Continental Drift

22. Evidence for Continental Drift
• Despite all of the evidence, Wegener
could not provide a satisfactory
explanation for the pushes/pulls of
continents so his theory was rejected
even up until the 1960’s.

27. Section 5-4
Sea-Floor
Spreading

28. Mid-Ocean Ridge
•The earth’s longest mountain range is
underwater! It is called the mid-ocean ridge
system that was discovered using sonar (sound
navigation and ranging) in the mid-1900’s.
•Sonar bounces sound waves off the ocean floor
and records the how long it takes for an echo to
determine distances.

29. Mid-Ocean Ridge
•In the mid-ocean ridge system, is a deep
central valley with mountain peaks on both
sides.
•What happens at these ridges?

30. What Is Sea-Floor Spreading?
•In the 1960’s Harry Hess and others studied the
mid-ocean ridge and proposed the theory of sea-
floor spreading:
********At the mid-ocean ridge, magma erupts from
the mantle, cools, and older rock moves outward on
both sides, adding new oceanic crust to each
side.********

31. What Is Sea-Floor Spreading?
•As a result, the ocean floors
move like conveyor belts,
carrying the continents along
with them.

32. Evidence for Sea-Floor Spreading
Several types of evidence support the theory of
sea-floor spreading:
1. Pillow Lava-
• When lava that erupts in the ocean hits cold
water it cools quickly and forms characteristic
pillow shapes. This “Pillow Lava” has been
found at mid-ocean ridges.

33. Evidence for Sea-Floor Spreading
2. Magnetic stripes in the rock
of the ocean floor
•When rock cools, any iron in
the rock becomes magnetized
in direction of earth’s
magnetic field. The rock has
“magnetic memory”.
•For unknown reasons, the
earth’s magnetic field
periodically reverses itself.

34. Evidence for Sea-Floor Spreading
•According to sea-floor spreading, new rock is being added
in equal amounts to both sides of the mid-ocean ridge.
•Therefore, it is expected that rock strips of equal size and
magnetism should be parallel to each other on both sides of
the ridge.
•Scientists have used sensitive instruments that show that
the “magnetic memory” of the rocks does alternate and is in
the same pattern on both sides of the ridge.
•Because is found to be true, this is strong evidence for sea-
floor spreading.

35. http://www.windows.ucar.edu/tour/link=/earth/interior/seafloor_

36. Evidence for Sea-Floor Spreading
3. Drilling core samples-rock is
younger near the mid-ocean ridge and
gets progressively older moving away
from the ridge.
Glomar Challenger

37. Subduction at Trenches
•If ocean floor is constantly being
made at mid-ocean ridges, is the
Earth constantly getting bigger?

38. Subduction at Trenches
•Not only are there mid-ocean ridges in
the ocean, there are deep canyons in the
oceans called deep-ocean trenches.
•The further the ocean floor moves from
the ridges, the cooler and denser it
becomes.

39. Subduction at Trenches
•In a process taking tens of millions of years, cold,
dense ocean floor far away from mid-ocean ridges
sinks back into the mantle through deep-ocean
trenches. This process is known as subduction.

40. The Challenger Deep
• The Challenger Deep is the deepest point in the
oceans and is located at the Southern End of the
Mariana Trench. It is in the Pacific and is 6.78
miles deep!!

41. Subduction at Trenches
•In the Pacific ocean there are
more deep ocean trenches
than there are mid-ocean
ridges.
•In the Atlantic ocean there
are more mid-ocean ridges
than there are deep ocean
trenches.
•What is happening to the size
of the Pacific? The Atlantic?
•The Pacific is shrinking and
the Atlantic ocean is growing!
•Because of sea-floor
spreading, the distance
between Europe and North
America is increasing by a few
centimeters per year.

44. Section 5-5
The Theory of
Plate Tectonics

45. Plates
•The lithosphere (crust and upper mantle) is broken into
sections called plates.
•These plates fit together along cracks in the
lithosphere.
•Plates can contain continents, the ocean floor, or both.

46. Plates
•The mid-ocean ridge is actually one of these
cracks, a boundary between two plates. It is where
two different plates are moving away from each
other.

47. How Plates Move
•The theory of plate tectonics states that plates are in a
slow, constant motion driven by convection currents in
the earth’s mantle.
•Convection currents in the mantle cause some warm
magma to rise and erupt at the mid-ocean ridge.
•Convection currents push and pull the tectonic plates
as shown in the diagram.

48. Plate Boundaries
•A plate boundary is where different plates
meet. At a plate boundary, plates can collide,
pull apart, or grind past each other.

49. Transform Boundaries
1. A transform boundary is a place where
two plates slip past each other, moving in
opposite directions. This boundary or break
in the rock is called a fault.
•Crust is neither created nor destroyed
•Earthquakes occur frequently along these
boundaries.

50. Transform Boundaries
•The San Andreas Fault is
a transform boundary in
California where the North
American Plate and the
Pacific plate are moving
past each other.
•Scientists predict that in
10 million years LA and
San Francisco will pass
each other!
•Right now, scientists are
more concerned about
earthquakes that are
triggered by the
movement.

51. Divergent Boundaries
•The place where two plates move apart, or
diverge, is called a divergent boundary.
•The mid-ocean ridge is a divergent
boundary-each side of the ridge is actually a
different plate.

52. Divergent Boundaries
•If Divergent boundaries form on land,
they stretch and thin the crust creating
rift valleys.
•Ex. Iceland and the Great Rift Valley in
Africa.

54. Convergent Boundaries
•The place where two plates come together, or
converge, is called a convergent boundary.
Trenches, or subduction zones are convergent
boundaries!
•At a convergent boundary, what happens
depends on the density !
•Oceanic crust (mainly basalt) is always more
dense than continental crust (mainly granite).
******Whatever plate is denser, sinks
underneath the other plate!

55. Convergent Boundaries
There are 3 types of collisions at
convergent boundaries:
1. Continental / Continental-
• Same density
• Neither plate really
subducted!
• Folded mountains form
• Ex. India collided with Asia to
form the Himalayas 60 mya
and is still colliding today!
• Ex. North America collided
with Europe and Northern
Africa during the formation of
Pangaea to form the
Appalachians.

56. Convergent Boundaries
2. Oceanic / Continental-
•Oceanic plate denser
•Oceanic plate is subducted and melting creates
Volcanoes/Volcanic Mountains on the land
•Ex. Mt. Saint Helens

57. Convergent Boundaries
3. Oceanic /Oceanic-
•Whichever plate is denser is
subducted and melts creating
volcanoes which may build up into
volcanic islands or “island arcs”
•Ex. The Philippines

58. So how did marine fossils end up
embedded in rock at the top of Mount
Everest?
•As India moved closer to Asia,
the ocean between them was
subducted and became smaller
and smaller, eventually becoming
very narrow.
•In that narrow strip of ocean
were marine organisms that lived
and died. Their shells were
fossilized in the rock on the ocean
floor.
•Then, when India finally collided
with Asia, some of the fossils got
driven up with the rest of the
continental crust and over
millions of years it was pushed up
5 miles to the “top of the world.”

59. Rate of Plate Movement
•Using GPS technology to repeatedly measure
distances between specific points, geologists
can very accurately determine the movement.
between plates.

61. Big Picture
•It has taken the continents about 225
million years since the breakup of Pangaea
to move to their present locations.

62. End of
Chapter!