LECTURE 1 Introduction Hrvoje Tkali N B The

LECTURE 1 - Introduction Hrvoje Tkalčić *** 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 Power. Point presentation is not a complete lecture; it is

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.

Time How are relative ages of rocks classified? Fossils (remnants of prehistoric life succeed each other in systemic fashion) How are absolute ages of rocks determined? Radioactive isotope dating

Time… -> Fossils This evolution is a clock of relative time, called the Principle of faunal succession. OLDEST one-celled organisms multi-celled organisms allows geologists to identify rocks of same age in different places. organisms with shells fishes plants insects amphibians reptiles YOUNGEST mammals

Geologic Time � Chart

If the entire Earth’s history were scaled to 1 year… The appearance of planet Earth -around 4: 15 pm the first hominids appear in East Africa
 -between 8 pm and 9 pm, the first humans appear in Africa -at 8: 04 pm, humans make their first tools -around 8: 30 pm, they make their first shelters -between 9 pm and 10 pm, humans arrive to Europe

Geologic time

Atoms, minerals and rocks rock minerals mineral collection of one or more minerals A collection of one or more types of atoms

Atoms, minerals and rocks F Atomic structure Example: mineral quartz made up of silicon (Si) & oxygen (O) atoms 2 - O 4+ Si 2 - O

Atoms, minerals and rocks Example: Granite & constituent minerals Rocks § Sedimentary § Igneous § Metamorphic

Average composition of the continental crust Percent of elements by WEIGHT

Average composition of the continental crust Percent of elements by VOLUME

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

Dynamic Earth: how did plate tectonics concept developed? 16 th century observation of coastal fits RE Alfred Wegener 1912 J Emismatch observed of climate C features T Proposed “continental drift” E D Pangea = Laurasia + Gondwana ! Same fossils found on different continents

Mid-Ocean ridges

Earthquake distribution and focal mechanisms

The Earth’s Interior CRUST Oceanic 0 -6 km (“young”, < 180 m. y. ) Continental 0 -34 km (older, up to 3. 8 b. y. ) MANTLE Upper 34 -670 km Lower 670 -2900 km Brittle “lithosphere” Plastic flow “astenosphere” CORE Outer (liquid) 2900 -5160 km Inner (solid) 5160 -6370 km

Maxwell’s equation and its implication for the geodynamo: Sea floor spreading from the age of rocks and the magnetic “stripes” due to the magnetic field reversals “Conveyor belt” concept by H. Hess (1960) Continents with no “plow experience”

Plate tectonics and boundaries Active Earth movie Continental and oceanic crust Collision may cause: • Faulting • Earthquakes • Mountain building • Volcanoes

Plate tectonics and boundaries Structural contrasts §Tonga-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 Active Earth movie

Plates

slower than average faster than average

Study of the deep Earth’s interior requires a multidisciplinary approach +Geodesy +Mathematical geophysics +Geomagnetism +Geochemistry +Geology +Computer science