GEOL 240Lg 1st Edition Lecture 1Outline Current Lecture I. Definition of scienceII. What is a “Paradigm”?III. Who is George Mendel? IV. Introduction to what are Plate Tectonics and Earthquakes V. 1960’s Revolution in Earth Science VI. Defining edges of Tectonic Plates VII. Fault PlanesCurrent Lecture- A theory in science is a hypothesis, which is what makes science.- Science is simply taking observations and testing them out like pot shots.- You conduct many experiments until you reach the point when the hypothesis has much data and is ironed into a theory.- In science and all encompassing idea or set of practices that define a scientific discipline.- Humans have been doing this for 10,000 years been doing this in trial and error until Gregor Mendel did his experiments.- Gregor Mendel (1822- 1884) the father of modern genetics. He spent his entire life cross breeding peas. His hypothesis wasn’t accepted during his lifetime. His studies helped humanity understand biology.- Why are we talking about this? Because earth sciences went through a similar shift called THE ADVENT OF PLATE TECTONICS- In 1960 if you pulled all the scientists in the world all this was ridiculed as nonsense but by1970’s, 99% believe plate tectonics thought this was this right.- How did we go from thinking this was nonsense to right? This is how science is…it takes times to be proven right.- 1965-1970 there was a complete revolution in earth science ...complete shift in how people were thinking about plate tectonics --> this revolution explains mountains and everything…even volcanoes, distribution of volcanoes, why we have oceans and why we have continents … why are the ocean levels low and continents high. - It also explains why some floors of the world’s oceans are low- What’s an earthquake? -> It is the sudden slippage of one block of rock past another alonga fault.- A fault is a failure in the rock, a crack in the rock What makes it a fault? = A crack in the rock that had slip of the blocks on either side past each other. --> The sudden slip generates seismic waves The passage of these waves causing the shaking we feel as an earthquake So faults are only there from earthquakes. If no earthquakes occur then they are just cracksEarthquakes don’t occur just anywhere around the world-- They occur in very well defined areas-- Most of earth has very few earthquakes (earthquake belts)90% of the energy released in earthquakes around the world is around the Pacific Ocean belts - Some of these belts are really narrowly, designed. (Ocean)- Other belts mostly next to (continents) are much wider. 3rd type of belt are really messy...mainly in Southern Asia. really wide and spread out Bathymetry (underwater photography) - Bathymetric studies show that these narrow mid-ocean earthquake belts correspond to mid-ocean undersea mountain chains Wider belts around Pacific Rim--> Earthquakes extend from near seafloor to as much as 700km depth --> These earthquakes correspond to oceanic trenches (e.g., Marianas trench)Where we are (California) we only have shallow earthquakes!--> These belts are closely associated with most of the world’s volcanoes.The point at which an earthquake starts is hypocenter, this is when the fault starts slipping.These really shallow earthquakes generally don’t cause damage.We worry about the surface earthquakesEpicenter-> the point on the surface directly on top of hypocenter.Earthquake belts define edges of tectonic plates1) Eq belts define the edges of ~(about) 12 tectonic plates1) ~ 100km thick2) Thin, rigid “skin” of the earth3) The plates constitute what we call the lithosphere4) Rigid lithospheric plates move relative 2 one another above a weak slushy layer called the asthenosphere.I. All tectonic activities -> Earthquakes, mountains, volcanoes occur at boundaries beneath atmospheric plates --> Tectonic - Greek “ tectos”= builderI. 3 types of plate boundariesDivergent= where 2 plates move apart (or diverge) Convergent = where 2 plates move towards each other (or converge)- Transform= plates move horizontally past each other accommodate space problems associatedwith spherical earth)FAULT AREN’T LINES... THEY ARE