Introduction to Earth System

1
Introduction to Earth System

• Solid Earth part
• Rocco Malservisi
• roccom_at_lmu.de
• Phone [phone]

http//www.geophysik.uni-muenchen.de/Members/malse
rvisi/lectures/earth_system_2008
2
NEU PINAKOTEK
ALTE PINAKOTEK
PINAKOTEK DER MODERNE
My office Theresienstr. 41 office 402
roccom_at_lmu.de Phone [phone]
3
SYSTEM A set of objects or characteristics which
are related to one another and which operate
together as a complex entity.

• A system may
• be composed of numerous smaller systems and/or
• form part of a larger system

• The system reacts to driving force that
  represents the application of energy on the
  resisting framework
• 2 types of driving forces
• Exogenic from the outside
• Endogenic from the inside

So if we want to study the system (or a
subsistem) we need to define the boundary
4
For the solid earth system we consider everything
related To atmosphere or idrosphere as
external. It is important to think that the
interaction between the solid Part of the planet
and the outer shells can be very important And in
many study it is considered a system a
part. Geomorphology is mainly the science that
study this interaction.
NASA photo from Apollo 17
5

• Which shape has the planet?
• What can we see (colors)?
• What can we measure?

6

• Is it really a sphere?
• Is it an ellipsoid?
• Is it flat?
• The shape of our system depend on the problem we
  want to study and the required precision!!

7

• How big is the planet?

8

• How big is the planet?
• By definition 40000 km!!
• 1m1/4e6 length of a meridian.
• Or 60x360 nautical miles (21600 nm).

9

• How big is the planet?
• By definition 40000 km!!
• The first one to measure it correctly
  Erstosthenes measuring the distance from
  Alexandria and Syene (5000 stadia) and the angles
  in figure, he computed a circumference of 250000
  stadia 39300km

From Marshak, 2005
10

• How big is the planet?
• By definition 40000 km!!
• Today we say that the radius of the Spherical
  Earth equivalent to the volume of the planet is
• 6371 km
• We also know that an ellipsoid is a better
  approximation
• Eq radius 6378 km
• Pol Radius 6356 km
• Flattening 1/298

From Marshak, 2005
11

• Which shape has the planet?
• How big is the planet?
• What is its mass?

12

• We are attracted to it and there is gravity

http//www.jadetower.org/muses/wlsimages/gravity-n
ewton.jpg
13

• We are attracted to it and there is gravity
• And if we look at the satellite it is falling in
  to the Earth attracted by a force that is
  proportional to the mass of the planet.
• From the orbit parameter we can compute the mass

http//www.jadetower.org/muses/wlsimages/gravity-n
ewton.jpg
14

• Well even from the ground if we know the constant
  G and our distance from the center of the Earth
  we can measure the gravity acceleration thus the
  mass of the Earth (ex a pendulum)
• MgR2/G
• g9.8ms-2
• G6.67e-11 m3kg-1s-2
• R6371km
• M6e24 kg

http//www.jadetower.org/muses/wlsimages/gravity-n
ewton.jpg
15

• So can we say something about the interior of the
  planet?
• what is the average density?
• Mass 6e24 kg
• Volume ?

16

• So what is the average density?
• Mass 6e24 kg
• Volume4/3pR3
• 1.08e21 m3
• So its density is
• 5500 kg m-3
• Density of surface rocks?

17

• So what is the average density?
• Mass 6e24 kg
• Volume4/3pR3
• 1.08e21 m3
• So its density is
• 5500 kg m-3
• Density of surface rocks?
• 1.5-3.5 g/cc
• Density Iron 7g/cc

18

• Which shape has the planet?
• What can we see (colors)?
• What can we measure?

19

• We have a magnetic field that it is very similar
  to the one of a dipole.
• Well in reality this is true close to the surface
  if we go far away enough it looks more complex

Magnetopause 10Re Moon 60Re
20
Variation of Magnetic field on oceans
Looking for subs the British and Americans
developed a map of Magnetic anomalies of the sea
floor, in 1961 Harry Hess explained It using
seafloor spreading theory.
21
Müller et al. 2006
Magnetic and gravity anomalies and
topo/bathymetry
GGM01S, GRACE mission www.csr.utexas.edu/grace/gra
vity/
22
Lets try to look more in details the brownish
regions
23
Lets try to look more in details the brownish
regions
hypsographic curve
www.waterencyclopedia.com
24
Lets try to look more in details the brownish
regions
Some area are flat and some are rough
Some areas look like if someone enjoyed to fold it
Some area are more brownish then other
25
Lets try to look more in details the gravity
What does influence this variation of gravity
field?
26

• So as first approximation the Earth is a planet
  that looks like a sphere with a density higher
  than we would expect looking only at the surface,
  with regions of different colors at the surface
  and able to generate a dipolar magnetic field.
  That does not appear to be constant.

27
So it does not look any longer as an homogeneous
sphere!! On second approximation it is an
ellipsoid 6357 km (polar) 6378 km
(equatorial) And it looks like if some processes
are shaping the brownish regions. We will spend
the rest of the semester (for my part) to look At
these processes and to figure out how we can
observe them How does it change with time??
28

• Meteosat images 2008/10/25 (last saturday) at
• 1800 GMT 1400 GMT
• The white spot moves on the scale of hours!
• What about the brownish region (marked by the
  white line)? They seems fixed.

29
What about the blue part?
So we have changed on different time scales
30

• What about the brownish region (marked by the
  white line)? They seems fixed.
• In reality if we would be able to make a very
  accurate measurement we would see that a point in
  africa and a point in South America would have
  moved 15 mm (3cm/yr)

31
If we would have been able to take picture in the
past we would have been able to see a different
picture
200 Ma
From Marshak, 2005
32
So we have different time scales we can look at
the processes
Some processes are almost instantaneous Some
processes have time scale of hours or days Some
processes on the order of months or years Other
processes in thousands or millions of years
geological processes are in general on this scale
33
THIS MEANS THAT TO STUDY THE EARTH SYSTEM WE MUST
LOOK AT MANY DIFFERENT TIME SCALE DEPENDING
WHICH PROCESS WE WILL LOOK AT. WE HAVE A TIME SO
LONG THAT EVEN VERY SLOW PROCESSES CAN HAVE
SIGNIFICANT IMPACT. THE SPATIAL SCALE PLAY ALSO
A MAJOR ROLE IN UNDERSTANDING THE DIFFERENT
PROCESSES.
34
Time scale for solid earth processes
Differentiation Billions of years Motion of the
mantle Millions of years Motion of the Surface
Millions of years Creation or destruction of a
mountain Millions of years Volcanic Eruption
Minutes/days Earthquakes Loading (thousand of
years) Earthquake seconds/minutes Landslide
seconds/months
35
Space scale for solid earth processes
Differentiation full Earth Motion of the mantle
Global Motion of the Surface Global/hundred of km
Creation or destruction of a mountain hundreds m
km Volcanic Eruption km Earthquakes Loading
(thousand of years) m km Earthquake
seconds/minutes m km Landslide seconds/months m km