07-01-2014, 12:51 PM
LITHOSPHERE : MAGNETIC FIELD AND GRAVITY FIELD IN EARTH
LITHOSPHERE.pptx (Size: 2.68 MB / Downloads: 44)
INTRODUCTION OF THE LITHOSPHERE
Is the hard shell of the Earth, consisting of the crust and the topmost part of the upper mantle.
It is an average of 100km thick.
It contains the minerals, rocks and soils that humans have used for building materials, metals and agriculture.
GRAVITY FIELD
The Earth’s mass exerts an attractive force around the Earth called gravity.
The gravity field of the Earth is an equipotential surface.
We call this equipotential surface the geoid.
For general purposes, the mean sea level is assumed as the surface of the geoid.
There are two ways to measure gravity:
Absolute measurement
Relative measurement
A gravity anomaly is the difference between the observed reduced gravity and the normal gravity.
Normal gravity: perpendicular of the Earth’s gravitational force and the centrifugal force caused by the rotation of the Earth, theoretical value.
Observed reduced gravity: gravity measurement reduced to
sea level.
The difference is caused by the composition and topography of
the Earth, the Earth’s rotation (flattening of the poles), and the dynamic features of the Earth.
gravitational force between two objects determined by their masses and distance between them.
MAGNETIC FIELD
Generated by the convective motion the fluid outer core about the solid inner core.
The “North geographic pole” corresponds to the “south pole” of the imaginary bar magnetic so that the north needle on a compass points towards the north geographic pole