Introduction to Earth System

Introduction to Earth System Solid Earth part Rocco Malservisi malservisi@geophysik.uni-muenchen.de Phone: 2180 4201

NEU PINAKOTEK ALTE PINAKOTEK PINAKOTEK DER MODERNE My office: Theresienstr. 41 office 402 malservisi@geophysik.uni-muenchen.de 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. Well in reality this is true close to the surface if we go far away enough it looks more complex Magnetopause 10Re Moon 60Re

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 area are flat and some are rough Some areas look like if someone enjoyed to fold it Some area are more brownish then other

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 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 operatetogether 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

Introduction to Earth System