Chapter 5
Gravity
School of Earth and Environmental Sciences
Junkee Rhie
5.2 Gravitational potential and acceleration
Theory of gravity
1
5.2 Gravitational potential and acceleration
Theory of gravity
5.3 Gravity of the Earth
Gravitational acceleration on the Earth
2
5.3 Gravity of the Earth
Gravitational acceleration on the Earth
5.3 Gravity of the Earth
Orbits of satellites
3
5.4 Shape of the Earth
The geoid
5.4 Shape of the Earth
The geoid
4
5.4 Shape of the Earth
Earth’s gravity anomaly field
5.4 Shape of the Earth
Global topography (ETOP02)
5
5.5 Gravity anomaly
Geoid anomaly
5.5 Gravity anomaly
French Expedition (Pierre Bouger and Everest)
• Try to measure the length of a degree of latitude in Peru and near
Pairs in order to determine the shape of the Earth (1735-1745)
d  R(1   2 )
6
5.5 Gravity anomaly
5.5.2 Isostasy
5.5 Gravity anomaly
Airy’s hypothesis
7
5.5 Gravity anomaly
Pratt’s hypothesis
5.5 Gravity anomaly
Airy vs. Pratt
8
5.5 Gravity anomaly
Gravity corrections
5.5 Gravity anomaly
Latitude corrections
9
5.5 Gravity anomaly
Free-air correction
5.5 Gravity anomaly
Free-air anomaly
10
5.5 Gravity anomaly
Austrailia
5.5 Gravity anomaly
Bouguer correction
11
5.5 Gravity anomaly
Bouguer anomaly
5.5 Gravity anomaly
Austrailia
12
5.5 Gravity anomaly
Isostatic equilibrium
5.5 Gravity anomaly
Isostatic equilibrium
13
5.5 Gravity anomaly
Austrailia
5.5 Gravity anomaly
Buried sphere
14
5.5 Gravity anomaly
Ambiguity
5.6 Observed gravity and geoid anomalies
Mid-ocean ridge
15
5.6 Observed gravity and geoid anomalies
Ocean trenches
5.6 Observed gravity and geoid anomalies
Ocean trenches
16
5.6 Observed gravity and geoid anomalies
Subduction profiles
5.6 Observed gravity and geoid anomalies
Subduction profiles
17
5.6 Observed gravity and geoid anomalies
Subduction profiles
5.6 Observed gravity and geoid anomalies
Geoid height anomalies
18
5.6 Observed gravity and geoid anomalies
Gravity and convection
5.6 Observed gravity and geoid anomalies
Gravity and convection
19
5.6 Observed gravity and geoid anomalies
Gravity over Hawaii
5.6 Observed gravity and geoid anomalies
Lithospheric flexure
20
5.6 Observed gravity and geoid anomalies
The elastic plate
5.6 Observed gravity and geoid anomalies
The elastic plate
21
5.6 Observed gravity and geoid anomalies
The elastic plate
5.6 Observed gravity and geoid anomalies
Elastic thickness of oceanic plates
22
5.6 Observed gravity and geoid anomalies
Isostatic rebound
5.6 Observed gravity and geoid anomalies
Isostatic rebound
23
5.6 Observed gravity and geoid anomalies
Isostatic rebound
Measuring Gravity
GRACE (Gravity Recovery And Climate Experiment)
24
Measuring Gravity
GRACE (Gravity Recovery And Climate Experiment)
• Global ocean circulation
• Slow current of Magma
• Thinning of ice sheets
• Earthquake
• and much more
Earth’s Gravity Field Anomaly
25