Transcript Introduction

What’s Geophysics
• Understanding the Earth’s composition and
dynamics, and their relationships with the surface
geological phenomena, using the means of
Physics.
• Analogy: How do you figure out what is going on
inside an apple, egg, golf ball, human body,
without slicing it open? (Suggestions: you can
weigh it, spin it, heat it, probe it with
electromagnetism, etc. You can also look at what
is naturally emitted from it.)
Tapping the Earth
Gravity Recovery and Climate
Experiment (GRACE)
General Goals
• A modest foundation of factual knowledge about the Earth,
and a feeling for the size of things.
• A basic understanding of the underlying physical
principles for the observed Earth’s phenomena.
• An awareness of geophysical methodologies and how they
are combined to solve problems.
• An appreciation of the level of current knowledge in
geophysics, and the many exciting problems that still
remain to be tackled.
Why Geophysics?
• Human Nature.
• Related to our daily life.
• Necessary tools for economic applications.
Earth as a Planet
• Mass M = 6 x 1027 g.
• Radius R = 6371 km.
• Mean density = M/(4/3
p R3) = 5.5 g/cm3
• Moment of inertia I of
the Earth:
– I =  r2 dm
– I/(MR2) = 0.331.
– for a uniform sphere
I/(MR2) = 0.4.
Interior of the Earth
• Crust: variable thickness with an average value of
35 km in the continents and 7-8 km in the oceanic
regions. Volume ~1019 m3 Mass 2.8 x 1022 kg.
• Mantle: between the Moho discontinuity (crustmantle) and the core-mantle boundary (R = 3480
km). Volume 9 x 1020 m3 Mass 4 x 1024 kg.
• Core: from the center of the Earth to the coremantle boundary. Volume 1.77 x 1020 m3 Mass
1.94 x 1024 kg.