Presentation on theme: "*** 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."— Presentation transcript:
*** 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 - Introduction Hrvoje Tkalčić
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
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…
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 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 climate features Proposed “continental drift” Pangea = Laurasia + Gondwana 16 th century observation of coastal fits Same fossils found on different continents R E J E C T E D !
The Earth’s Interior CORE Outer (liquid) 2900-5160 km Inner (solid) 5160-6370 km MANTLE Upper 34-670 km Lower 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 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” Maxwell’s equation and its implication for the geodynamo:
Plate tectonics and boundaries Active Earth - movie Continental and oceanic crust Collision may cause: Faulting Earthquakes Mountain building Volcanoes
Plate tectonics and boundaries Active Earth - movie 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 boundary - thick lithosphere prevents secondary spreading.