Transcript Introduction to Earth System - uni

Introduction to Earth
System
Solid Earth part
Rocco Malservisi
[email protected]
Phone: 2180 4201
NEU
PINAKOTEK
ALTE
PINAKOTEK
PINAKOTEK
DER MODERNE
My office: Theresienstr. 41 office 402
[email protected]
Phone: 2180 4201
NASA photo from Apollo 17
Which shape has the
planet?
What can we see
(colors)?
What can we measure?
How big is the planet?
By definition 40000 km!!
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
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
From Marshak, 2005
Which shape has the
planet?
How big is the planet?
What is its mass?
We are attracted to it and
there is gravity
http://www.jadetower.org/muses/wlsimages/gravity-newton.jpg
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-newton.jpg
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
M=gR2/G
g=9.8ms-2
G=6.67e-11 m3kg-1s-2
R=6371km
M=6e24 kg
http://www.jadetower.org/muses/wlsimages/gravity-newton.jpg
So can we say
something about the
interior of the planet?
what is the average
density?
Mass = 6e24 kg
Volume = ?
So what is the average
density?
Mass 6e24 kg
Volume=4/3pR3=
1.08e21 m3
So its density is
~5500 kg m-3
Density of surface rocks?
So what is the average
density?
Mass 6e24 kg
Volume=4/3pR3=
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
Which shape has the
planet?
What can we see
(colors)?
What can we measure?
We have a magnetic field
that it is very similar to
the one of a dipole.
Magnetopause 10Re Moon 60Re
Well in reality this is true
close to the surface if
we go far away
enough it looks more
complex
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.
Let’s try to look more in details the brownish regions
Some
Somearea
areasare
look
flat
like
and
ifsome
someone
are
rough
enjoyed
Some
area
are
more
brownish
then
other to fold it
Let’s try to look more in details the gravity
What does influence this variation of gravity field?
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??
Meteosat images 2006/10/18 (yesterday) at
18:00 GMT
14:00 GMT
The white spot moves on the scale of hours!
What about the brownish region (marked by the
white line)? They seems fixed.
What about the blue part?
So we have changed on different time scales
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)
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
So we have different time scales we can look at the processes
Some processes are almost instantaneous
QuickTime™ and a
Graphics decompressor
are needed to see this picture.
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
How old is the eath?
Earth Birthday 0:00 on January 1st
Oldest known rock: Early February
First Bacteria: End of February
First Invertebrate: October 25th
First Animal on land: November 20th
Super Continent Pangea: December 7th
Dinosaurs December 15th to 25th
First Hominids: December 31st evening
First Homo sapiens 31 December 23:59
Written history 31 December 23:59:32
Roman Empire: 31.12. 23:59:45-23:59:50
Today: December 31st 24:00
1second+~150 yr
Geological Survey Bureau, Iowa Department of Natural Resources
How old is the eath?
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.
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

If there were no endogenic forces …
… the Earth would look like the Moon