*** N.B. The material presented in these lectures is from the principal textbooks, other books on similar subject, the research and lectures of my colleagues from various universities around the world, my own research, and finally, numerous web sites. I am grateful for some figures I used in this lecture to E. Garnero and L. Breger. I am thankful to many others who make their research and teaching material available online; sometimes even a single figure or an idea about how to present a subject is a valuable resource. Please note that this PowerPoint presentation is not a complete lecture; it is most likely accompanied by an in-class presentation of main mathematical concepts (on transparencies or blackboard).***

LECTURE 1 - IntroductionHrvoje Tkalčić

Units and scales

Time…

Time is a fundamental variable in geophysics.

Geophysical images of Earth’s surface and interior are snapshots of Earth’s dynamic processes.

How are relative ages of rocks classified?

How are absolute ages of rocks determined?

Radioactive isotope dating

Fossils (remnants of prehistoric life succeed each other in systemic fashion)

Time

This evolution is a clock of relative time, called the Principle of faunal succession.

Time… -> Fossils

allows geologists to identify rocks of same age in different places.

one-celled organisms

multi-celled organisms

organisms with shells

fishes

plants

insects

amphibians

reptiles

mammals

OLDEST

YOUNGEST

Geologic TimeChart

The appearance of planet Earth

-around 4:15pm the first hominids appear in East Africa-between 8pm and 9pm, the first humans appear in Africa-at 8:04pm, humans make their first tools-around 8:30pm, they make their first shelters-between 9pm and 10pm, humans arrive to Europe

If the entire Earth’s history were scaled to 1 year…

Geologic timeGeologic time

rockrock

collection ofone or moreminerals

mineral

A collectionof one or moretypes of atoms

minerals

Atoms, minerals and rocksAtoms, minerals and rocks

Example: mineral quartz made up of silicon (Si) & oxygen (O) atoms

Atoms, minerals and rocksAtoms, minerals and rocks

Atomic structure

Si4+

O2-

O2-

O2-O2-

Example:Granite & constituent minerals

Atoms, minerals and rocksAtoms, minerals and rocks

Rocks Sedimentary

Igneous Metamorphic

Average composition of the continental crustAverage composition of the continental crust

Percent of elements by WEIGHTPercent of elements by WEIGHT

Average composition of the continental crustAverage composition of the continental crust

Percent of elements by VOLUMEPercent of elements by VOLUME

Sedimentary rocksSedimentary rocks

Grand Canyon

Alps, Himalayas, etc. - consist of sedimentary rocks, laid down over many millions of years…But, in what sea were the Himalayan rocks deposited and how did they get sandwiched between India and the Asian landmass? In the geology textbooks of the mid twentieth century - there were no satisfactory answers.

Dynamic Earth: how did plate tectonics concept developed?

Alfred Wegener 1912 -observed mismatch of climatefeaturesProposed “continental drift”Pangea = Laurasia + Gondwana

16th century observation of coastal fits

Same fossils found on different continents

R E J E C T E D !

Mid-Ocean ridges

Earthquake distribution and focal mechanisms

The Earth’s Interior

CORE Outer (liquid) 2900-5160 kmInner (solid) 5160-6370 km

MANTLE Upper 34-670 kmLower 670-2900 km

CRUST Oceanic 0-6 km (“young”, < 180 m.y.)Continental 0-34 km (older, up to 3.8 b.y.)

Brittle “lithosphere”Plastic flow “astenosphere”

Sea floor spreading from theage of rocks and the magnetic “stripes” due

to the magnetic field reversals“Conveyor belt” concept by H. Hess (1960)

Continents with no “plow experience”

€

The force on a charge is r F = q ⋅(

r E +

r B ×

r v )

The law of electromagnetic induction : r E ⋅d

r s ∫ = −

d

dt

r B ⋅

r n

a

∫ da

Applying the Stokes theorem, r

∇ ×r E ⋅

r n da

a

∫ = −∂

∂t

r B

⎛

⎝ ⎜

⎞

⎠ ⎟⋅

r n

a

∫ da

⇒r

∇ ×r E = −

∂

∂t

r B How do these terms remain in balance?

Maxwell’s equation and its implication for the geodynamo:

Plate tectonics and boundaries

QuickTime™ and aCinepak decompressor

are needed to see this picture.

Active Earth - movie

Continental and oceanic crustCollision may cause:•Faulting•Earthquakes•Mountain building•Volcanoes

Plate tectonics and boundaries

Active Earth - movie

Structural contrastsTonga-Fiji islands arc with earthquakes occurring within the descending “slab”. Asthenosphere on both sides of the descending slab with convection, “drag” and secondary spreading.Andean volcanic arc with earthquakes at the slab-lithosphere boundary - thick lithosphere prevents secondary spreading.

Plates

slower than average

faster than average

+Geodesy+Mathematical geophysics+Geomagnetism+Geochemistry+Geology+Computer science

Study of the deep Earth’s interior requires

a multidisciplinary approach