Geological Oceanography

OCN 622

Gary McMurtry

GravityGravity

The Gravimeter

Lacoste & Romberg G-28 Gravimeter

(and why should we care?)

Gravity Anomaly

I.e., the nullhypothesis is it’s all granite!

Plumb Bob DeflectionInitially discoveredwhile surveying at base of Himalayas!

Plumb Bob Deflection

(Pendulum clock as a precise gravimeter!)

Latitude Correction

Rotation Correction

(Within the precision of modern GPS units)

Elevation or Free-Air Correction

Excess Mass or Bouguer Correction

Summary of Gravity Types (cont.)

Buoyancy and Isostasy

Transcontinental Gravity Survey

=> Simplified Model of Subduction

Free-Air and Bouguer Anomalies Over a Spreading Center

Gravity Profiles have

Contributedto our Models of the Earth’s

Interior

Earth-Core Formation

Models

Space Probe Gravity Models of Planets => Estimates of

Europa’s deep structure

From: NASA Galileo Jupiter Mission Images

Micro-gravity surveys

at Poas Volcano,Costa Rica

Rymer et al. (2000)

High-Res. Regional Gravity Maps by Tandem Satellite Surveys

R. A. Kerr, Science 325, 798 (2009)

Oops!

Global Gravity Anomalies Reveal Deep Earth Structure & History

From: GRACE Mission; http://www.jpl.nasa.gov/news/features.cfm?feature=11

Gravity Summary

Gravity Summary (cont.)

Gravity Summary (cont.)