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

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 (crust-mantle) 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 core-mantle boundary. Volume 1.77 x 1020 m3 Mass 1.94 x 1024 kg.