Transcript Elementary Earth Physics

Jean-Claude Mareschal
Fiona Darbyshire
Course outline
 Age and formation of Earth and planets. Origin of the elements.
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Formation of the moon. The early Earth. Geochronology. (JCM)
Shape and rotation of the Earth. Tides. (JCM)
The gravity field of Earth. Gravity anomalies. Isostasy. (JCM)
Heat flow, thermal regime, and the energy budget of the Earth.
(JCM)
Earth’s magnetic field. The geodynamo. (JCM)
Seismic wave propagation. Body and surface waves. Free
oscillations. (FD)
Seismicity of the Earth. Earthquake focal mechanisms. (FD)
Plate tectonics. (FD)
Seismic tomography: implications for geodynamics and mantle
convection. (FD)
Course objectives
 What do we want to know about Earth interior?
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Physical properties (density, elastic properties, viscosity, electrical
conductivity, …)
Pressure, temperature at depth
Chemical composition
Physical state (liquid, solid)
Equation of state
 How did it come to be what it is today?
 How does it work?
Feynman’s Lectures on Physics
(1962)
Some references
 Davies, G. F. Dynamic Earth: Plates, Plumes and
Mantle Convection, Cambridge University Press, 2000.
 Fowler, CMR, The Solid Earth: An Introduction to
Global Geophysics, 2nd Edition, Cambridge,
University Press, 2004.
 Stacey, F.D., and Davis, P., Physics of the Earth, 4th
Edition, Cambridge University Press, 2008.
 Bott, M.H.P. The interior of the Earth, 2nd Edition,
Edward Arnold, London, 1982
Useful information
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Instructors:
Fiona Darbyshire (20 October-1 December)
[email protected], [email protected]
514-987-3000x5054
Jean-Claude Mareschal (1 September-13 October)
[email protected],
[email protected]
 514-987-3000x6864
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Evaluation:
Midterm: 40% (15 October)
Final: 40% (TBA)
Homeworks: 20%
Units. Numbers.
SI unit
Practical unit
Conversion
factor
length
m
Light year
Parsec
1 LY= 1013km
1 pc = 3.1 1013km
Mass
kg
Time
s
yr
1 yr = 3.15 107s
acceleration
ms-2
Gal (cm s-2), mGal
1 mGal = 10-5 ms-2
Force
N (kg m s-2)
Energy
J (kg m2 s-2)
Calorie
1 cal =4.18J
Power
W (J s-1)
Pressure
Pa (N m-2)
bar, kbar
1 kbar= 108 Pa
Viscosity
Pa s
poise
1 poise = 0.1 Pa s
Temperature
K
deg C
T(C)= 273 +T(K)
Physical constants.
c
300,000 km s-1
G
6.67 10-11 N m2 kg-2
NA (Avogadro)
6.02 1023 mol-1
R (Gaz constant)
8.31 J mol-1 K-1
k (Boltzman) = R/NA
1.38 10-23J K-1
Numbers.
Mass Earth
5.97 1024 kg
Mean density
5,515 kg m-3
Mass Sun/Mass Earth
332,947
Mass Earth/Mass Moon
81
Solar density
1,408 kg m-3
Moon density
3.341 kg m-3
Numbers.
Distance
Time
Atomic unit
10-15
Solar day
86,400 s
Astronomical day
86,146 s
Last glaciation
10,000 yr
Man
2-4 Myr
Earth
4.5 Gyr
Universe
~15 Gyr
s
Earth radius
~6,400 km
Earth-Moon
~400,000 km
Earth-Sun
~150 106 km (8 min)
Nearest star
~ 4 LY
Galaxy
100,000 LY
Nearest galaxy
1,000,000 LY
Universe
1010 LY