1. AICE Environmental Management
UNIT 1: Lithosphere

2. GUIDED READING QUESTIONS
Define lithosphere.
Describe the internal structure of the earth, including the characteristics of the core, mantle, asthenosphere.
Differentiate between oceanic and continental crust.
Describe how seismic wave data provides evidence of earth structure. (a sketch might be useful)
Name the 7 major (primary) plates and the minor plate with the coolest name.
For each of the following plate boundaries, describe the characteristics of the boundary and the natural hazards/ geologic processes that tend to be associated with that boundary:
a. Destructive (Convergent)
b. Constructive (Divergent)
c. Conservative (Transverse)
How do convection currents relate to the plate movements?
Explain sea-floor spreading.
Discuss the following types of evidence that exists to support the plate tectonic theory (post-Pangaea plate movement):
a. Paleo-magnetism
b. Paleontology
c. Geographic fit

3. L.KQ.1.: What are the key elements of the structure of the Earth?
characteristics of the core, mantle, asthenosphere
difference between oceanic & continental crust
convection currents
seismic waves data as evidence
plate tectonics & major plates
types of plate boundaries
seafloor spreading
post-Pangaea plate movement evidence

4. BELLRINGER
If you journeyed to the center of the Earth, what do you think you would see along the way?

5. Earth’s Structure – The Layers Chemical Composition
GR #2
Earth’s Structure – The Layers Chemical Composition
divided into three layers
crust
mantle
core (inner & outer)

6. Earth’s Layers: The Crust
outermost layer of the Earth
5 to 100 km thick (thinnest layer)
made up of oxygen, silicon and aluminum (light minerals)
least dense

7. Continental vs. Oceanic Crust
GR #3
Continental vs. Oceanic Crust
Continental Crust
Oceanic Crust
located beneath land masses & under shallow seas
located beneath deep ocean
very thick – b/w 30 – 60 km
very thin – b/w 5 – 8 km
less dense (e.g. granite)
denser (e.g. basalt)

8. Earth’s Layers: The Mantle
layer of the Earth b/w the crust & the core
much thicker than the crust (2,900 km)
67% of the mass
more magnesium, less aluminum & silicon than crust
more dense than crust

9. Earth’s Layers: The Core
the central part of the Earth that lies below the mantle
makes up 33% of Earth’s mass
radius 3,430 km
made mostly of iron and smaller amounts of nickel (heavy minerals)
most dense layer

10. Earth’s Physical Structure

11. Earth’s Physical Structure – The Lithosphere
GR #1
Earth’s Physical Structure – The Lithosphere
outermost, rigid layer of the Earth
derived from the greek word “lithos” meaning rocky stone
divided into pieces called tectonic plates
made up of two parts
crust & upper part of mantle

12. Earth’s Physical Structure – The Asthenosphere
plastic layer of the mantle on which the tectonic plates move
made of solid rock that flows very slowly

13. Exploring the Earth – Using Seismic Waves
GR #4
Exploring the Earth – Using Seismic Waves
same waves that travel through Earth’s interior during an earthquake
use seismic waves to learn about Earth’s interior
altered by the nature of the material through which it travels
changes in speed & direction measured when passing through different layers
Tapping on a melon to see if it is ripe

14. https://youtu.be/aY6SG7GPAlo

15. ACTIVITY: Earth’s Structure Foldable

16. BELLRINGER How is heat transferred? What causes convection currents?
What causes convection currents in the Earth’s mantle?

17. Convection
Heat transfer caused by differences of temperature & density within a fluid
Liquid/gas is heated  particles move faster
Particles spread apart, taking more space and density decreases
Add image of density mass/volume

18. Convection: How is heat transferred?
Heating
Particles move faster
Spread apart taking up more space
Density decreases
Cooling
Particles slow down
Settle closer together
Density increases
Particles sink

19. VIDEO: Convection Currents
Flow that transfers heat within a fluid
Heating & cooling changes fluid’s density
Force of gravity sets convection currents in motion

20. Where do convection currents occur?
Geosphere – plate tectonics
Atmosphere – wind
Hydrosphere - water

21. Convection Currents – Geosphere Source of Energy
GR #7
Convection Currents – Geosphere Source of Energy
Heat generated from radioactive decay of elements deep interior of the Earth
Creates magma (molten rock) in asthenosphere
Magma drives plate tectonics

22. Has the Earth always looked like this?
If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle…..the shape of Africa and South America are a good example.
Distribute the Handout: Pangaea Puzzle.
Say:
The continents shown on the Pangaea Puzzle are not to scale. They
are in the approximate location as present day continents.
Label the continents. Some large islands, such as Madagascar and
Greenland, are not included
This is because they DID used to fit together!
The Earth as we see it today was not always like it is now. Land masses have pulled apart and joined together by the process we call Plate Tectonics….

23. How Continents Move Wegener’s Continental Drift
Hypothesis that all continents once formed a single landmass called a supercontinent
Began breaking apart 250 mya (Mesozoic Era)

24. THEORY: Plate Tectonics
theory that explains why & how continents move
study of the formation of features in Earth’s crust
Earth’s crust and upper mantle are broken into sections called plates
plates move around on top of the mantle like rafts

25. Two Types of Plates Ocean plates - plates below the oceans
Continental plates - plates below the continents
Remember lithosphere and asthenosphere

26. GR #5
The Major Plates

27. Plate Boundaries – Three Types
GR #6
Divergent (constructive)
Convergent (destructive)
Transform (conservative)
Firstly, there are three types of plate boundary, each related to the movement seen along the boundary.
Divergent boundaries are where plates move away from each other
Convergent boundaries are where the plates move towards each other
Transform boundaries are where the plates slide past each other.
Presenter: See diagrams for each - it is important to remember the names of the boundary types and the motion involved.

29. Divergent Boundaries a.k.a. constructive (new)
Boundary between two plates that are moving apart or rifting
 
RIFTING causes SEAFLOOR SPREADING

30. Features of Divergent Boundaries
Mid-ocean ridges
rift valleys
fissure volcanoes

31. Age of Oceanic Crust Where are ocean ridges located?
ICELAND
Where are ocean ridges located?
Where are the divergent boundaries?
Ocean Ridges: This map shows the age of the oceanic crust. The red coloring shows the youngest ages, whilst the dark blue shows the oldest ages (around 200 million years old).
Presenter ask: Where are the Ocean Ridges located? I.e. where are the divergent boundaries?
Answer: The divergent boundaries are where the plates are pulling apart and new material is being produced. Therefore the Ocean ridges are in the middle of the red areas (the boundaries are in fact shown on the map). We can see a progression of the oceanic crust getting older away from the ocean ridges (like a conveyer belt).
Presenter: Before moving on to the next slide, point out Iceland. The divergent boundary runs straight through Iceland….
Courtesy of
Red color = youngest, dark blue = oldest

32. Iceland: example of continental rifting
Iceland has a divergent plate boundary running through its middle
Iceland is located right on top of a divergent boundary. In fact, the island exists because of this feature.
As the North American and Eurasian plates were pulled apart (see map) volcanic activity occurred along the cracks and fissures (see photographs).
With many eruptions over time the island grew out of the sea!
Question: Why don’t we have islands like Iceland where ever we get an Ocean Ridge?
Answer: Scientists believe that there is a large mantle plume (an upwelling of hot mantle material) located right underneath where Iceland has formed. This would mean that more material would be erupted in the Iceland area compared with if there was just the divergent boundary without the plume underneath it.

33. Did you know that the Earth’s longest mountain range is underwater and is called the mid-ocean ridge?
The Mid-Ocean Ridge system, shown above snaking its way between the continents, is more than 56,000 kilometers (35,000 mi) long. It circles the earth like the stitching on a baseball!

34. Convergent Boundaries
a.k.a. destructive
Boundaries between two plates that are colliding
 
There are 3 types…
Continent-oceanic
Ocean-ocean
Continent-continent

35. Type 1: Ocean - Continent
Ocean plate colliding with a less dense continental plate
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 centimetres per year. This oceanic crust is called the “Subducting Slab” (see diagram).
When the subducting slab reaches a depth of around 100 kilometres, it dehydrates and releases water into the overlying mantle wedge (Presenter: explain all of this using the diagram).
The addition of water into the mantle wedge changes the melting point of the molten material there forming new melt which rises up into the overlying continental crust forming volcanoes.
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.

36. Subduction
Oceanic lithosphere subducts underneath the continental lithosphere
Oceanic lithosphere heats and dehydrates as it subsides
The melt rises forming volcanism
E.g. The Andes
The Andes mountain range along the western edge of the South American continent is an example of a mountain belt formed by subduction.
The continental crust of the South American plate has buckled under the compressional strain of converging with the Nasca and Antarctic plates. Additionally there are many volcanoes, the result of melting of the subducting slab and the production of new material that has risen through the crust to the surface.

37. Andes Mountains, South America

38. Type 2: Ocean-Ocean
The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH
worlds deepest parts of the ocean are found along trenches
E.g. The Mariana Trench is 11 km deep!
When two oceanic plates converge, because they are dense, one runs over the top of the other causing it to sink into the mantle and a subduction zone is formed.
The subducting plate is bent down into the mantle to form a deep depression in the seafloor called a trench.
Trenches are the deepest parts of the ocean and remain largely unexplored.

39. Manned or unmanned submersible vehicles (top right photo) have explored small parts of trenches discovering new species (like the fish photographed here) and amazing ecosystems.

40. Type 3: Continent-Continent
continental plate colliding with another continental plate
Have Collision Zones:
a place where folded and thrust faulted mountains form.
Forms mountains (European Alps, Himalayas)
When continental crust pushes against continental crust both sides of the convergent boundary have the same properties (think back to the description of continental crust: thick and buoyant). 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. For example, the European Alps and Himalayas formed this way.

42. Himalayas
Example:
India used to be an island, but about 15 million years ago it crashed into Asia (see map).
As continental crust was pushing against continental crust the Himalayan mountain belt was pushed up.
“Mountains” were also pushed down into the mantle as the normally 35 km thick crust is approximately 70 km thick in this region.
Mt Everest is the highest altitude mountain on our planet standing 8,840 metres high. This means that below the surface at the foot of the mountain the crust is a further 61 km deep!!

43. Transform Boundaries a.k.a conservative
where plates slide past each other
earthquakes along faults
The third type of boundary are transform boundaries, along which plates slide past each other.
The San Andreas fault, adjacent to which the US city of San Francisco is built is an example of a transform boundary between the Pacific plate and the North American plate.
Above: View of the San Andreas transform fault

45. San Andreas Fault, CA

46. This map summarises all the known plate boundaries on Earth, showing whether they are divergent, convergent or transform boundaries.

47. ACTIVITY: Plate Tectonic GIZMO
Website explorelearning.com

48. Continental Drift Wegener’s Theory
Hypothesis that all continents once formed a single landmass called a supercontinent
Began breaking apart 250 mya (Mesozoic Era)

49. Wegener searched and found three main pieces of evidence.
GR #9
Wegener searched and found
three main pieces of evidence.
Geologic - evidence in the layers
of rocks across continents
Fossil - evidence in the places
certain fossils are found
Climate - evidence in the changing
climates during the past

50. GR #9
Geologic
Evidence
Fit of Continents Across the Atlantic Mountain ranges in South America line up exactly with those in Africa!

51. Fossil Evidence GR #9 Notice how fossils lined up across continents!
Notice how fossils lined up across continents!

52. Climate change Amazing Facts: Did you know...
...that India was once in the Southern Hemisphere connected to Antarctica?
...that North America was once surrounded by warm, tropical seas?
...that Africa was once covered by glaciers, which were kilometers in thickness?
...that the Sahara desert was once a tropical rain forest?

53. An example of the proof for changing climate:
At one time, the area that is New Mexico was below the equator!
As North America has drifted to different latitudes, changing climates were experienced. This shows the changes in the state of New Mexico.

54. Wegener: Doubted by ALL
could not find the force that was causing the continents to drift
could not convince anyone that continents could move
died in Greenland on an expedition; no one believed him
Technology developed during the 1940’s changed all that!

55. Discovery of Seafloor Spreading

56. Amazing proof of that the inner core flips! GR #8
As the sea floor spreads, the lava cools according to the magnetic poles at the time. The rocks on the ocean floor have proved that the earth’s magnetic field sometimes reverses. The inner core flips and so the north pole moves to the southern hemisphere! The earth itself does not flip.

57. Animation of sea floor spreading
Can you explain this diagram!?

58. This is a model of sea floor spreading at a divergent boundary called a mid ocean ridge.