chapters 5, 6, 13, 14, 21, 22 section 4 for hominid evolution 1

Chapters 5, 6, 13, 14, 21, 22

Section 4 for Hominid evolution

1

Earth’s Interior Layers•Crust: • 5-90 km thick• Continental and

oceanic

2

• Mantle• composed largely

of peridotite• dark, dense

igneous rock • rich in iron and

magnesium

• Core• iron and a small

amount of nickel

Earth’s Interior Layers3

• Lithosphere• solid upper

mantle and crust• broken into

plates that move over the asthenosphere

• Asthenosphere• part of upper

mantle• behaves

plastically and slowly flows

Earth’s Crust

•Continental

4

• (20-90 km thick) • density 2.7 g/cm3

• contains Si, Al• Oceanic • (5-10 km thick)• density 3.0 g/cm3 • composed of basalt

Plate Tectonic Theory

•Lithosphere is broken into individual pieces called plates

5

• Plates move over the asthenosphere – as a result of underlying convection

cells

Geology and the formulation of theories

•What is a theory?• It is arrived at through the scientific method,

which involves: • gathering and analyzing facts• formulating hypotheses to explain the phenomenon• testing the hypotheses• and finally proposing a theory.

• The hypotheses is a tentative explanation.• A scientific theory is a testable explanation for

some natural phenomenon, that is supported by a large body of evidence.

6

Modern Plate Map7

Plate Tectonic Theory

•At plate boundaries• Volcanic activity occurs• Earthquakes occur

•Movement at plate boundaries • Plates diverge• Plates converge• Plates slide sideways past each other

8

Plate Tectonic Theory•Types of plate boundaries

Transform

Divergent

Cont.-Cont.Convergent Cont.-Ocean

Convergent

Ocean-oceanConvergent

Ridge

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• There are convection cells (currents) in the mantle

The upper part of the mantle and the crust

10

• There are currents in the mantleA Subduction Zone• When the currents in the mantle carry one plate down -• It melts and volcanoes are produced

11

A Subduction Zone• Sometimes the molten rock cools down below the surface

12

Continental Collision• When two plates carrying continents collide mountain chains

are built

13

An Oceanic Ridge• If plates are being destroyed, new plate material must be being made somewhere

else - • At new plate margins

14

Click on the image to launch ‘What Wegener Knew’ PowerPoint

What Wegener knew: an example of ‘how science works’

15

Evidence for the structure of the Earth

19

Launch of a depth charge

20

Earthquake damage

21

The lithosphere (!)

24

Evidence for plate tectonics

25

Convection in the lab

26

Modelling the mantle

28

Mid-Atlantic ridge

http://maps.grida.no/go/graphic/world-ocean-bathymetric-map(Hugo Ahlenius, UNEP/GRID-Arendal)

29

Icelandic-type eruption

Reproduced with kind permission of U.S. Department of Interior, U.S. Geological Survey

30

Black Smokers

31

Pillow lavas

32

Research ship used to tow magnetometer

34

The equipment used

35

Island arc volcanism: Zavadovski Island

42

Ocean-continent convergence: Mount St Helens

Courtesy of USGS/Cascades Volcano Observatory

44

Folds at Lhotse (Himalayas)

46

Plate Tectonic Theoryinfluence on geological sciences:

•Revolutionary concept• comparable to evolution

•Provides a framework for • interpreting many aspects of Earth on a global

scale• relating many seemingly unrelated phenomena• interpreting Earth history

48

Plate Tectonics and Earth Systems

• plate tectonics is driven by convection in the mantle and in turn drives mountain building • and associated igneous and metamorphic activity

• arrangement of continents affects:• solar heating and cooling, • and thus winds and weather systems

• rapid plate spreading and hot-spot activity may release volcanic carbon dioxide and affect global climate

Solid

Ear

th49

Plate Tectonics and Earth Systems

• continental arrangement affects ocean currents• rate of spreading affects volume of mid-oceanic

ridges and hence sea level• placement of continents contributes to the onset

of ice ages

• movement of continents creates corridors or barriers to migration, the creation of ecological niches, and transport of habitats into more or less favorable climates

Hyd

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Bio

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chapters 5, 6, 13, 14, 21, 22 section 4 for hominid evolution 1

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