1

Chapter 5

Gravity

School of Earth and Environmental SciencesSchool of Earth and Environmental SciencesJunkee Rhie

5.2 Gravitational potential and accelerationTheory of gravity

2

5.2 Gravitational potential and accelerationTheory of gravity

5.3 Gravity of the EarthGravitational acceleration on the Earth

3

5.3 Gravity of the Earth Gravitational acceleration on the Earth

5.3 Gravity of the Earth Orbits of satellites

4

5.4 Shape of the EarthThe geoid

5.4 Shape of the EarthThe geoid

5

5.4 Shape of the EarthEarth’s gravity anomaly field

5.4 Shape of the EarthGlobal topography (ETOP02)

6

5.5 Gravity anomalyGeoid anomaly

5.5 Gravity anomalyFrench 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)

)( 21 Rd

7

5.5 Gravity anomaly5.5.2 Isostasy

5.5 Gravity anomalyAiry’s hypothesis

8

5.5 Gravity anomalyPratt’s hypothesis

5.5 Gravity anomalyAiry vs. Pratt

9

5.5 Gravity anomalyGravity corrections

5.5 Gravity anomalyLatitude corrections

10

5.5 Gravity anomalyFree-air correction

5.5 Gravity anomalyFree-air anomaly

11

5.5 Gravity anomalyAustrailia

5.5 Gravity anomalyBouguer correction

12

5.5 Gravity anomalyBouguer anomaly

5.5 Gravity anomalyAustrailia

13

5.5 Gravity anomalyIsostatic equilibrium

5.5 Gravity anomalyIsostatic equilibrium

14

5.5 Gravity anomalyAustrailia

5.5 Gravity anomaly Buried sphere

15

5.5 Gravity anomaly Ambiguity

5.6 Observed gravity and geoid anomaliesMid-ocean ridge

16

5.6 Observed gravity and geoid anomalies Ocean trenches

5.6 Observed gravity and geoid anomalies Ocean trenches

17

5.6 Observed gravity and geoid anomalies Subduction profiles

5.6 Observed gravity and geoid anomalies Subduction profiles

18

5.6 Observed gravity and geoid anomalies Subduction profiles

5.6 Observed gravity and geoid anomalies Geoid height anomalies

19

5.6 Observed gravity and geoid anomalies Gravity and convection

5.6 Observed gravity and geoid anomalies Gravity and convection

20

5.6 Observed gravity and geoid anomalies Gravity over Hawaii

5.6 Observed gravity and geoid anomalies Lithospheric flexure

21

5.6 Observed gravity and geoid anomalies The elastic plate

5.6 Observed gravity and geoid anomalies The elastic plate

22

5.6 Observed gravity and geoid anomalies The elastic plate

5.6 Observed gravity and geoid anomalies Elastic thickness of oceanic plates

23

5.6 Observed gravity and geoid anomalies Isostatic rebound

5.6 Observed gravity and geoid anomalies Isostatic rebound

24

5.6 Observed gravity and geoid anomalies Isostatic rebound

Measuring GravityGRACE (Gravity Recovery And Climate Experiment)

25

Measuring GravityGRACE (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