Geo First Chapters PDF

Mod 2: Plate Tectonics Ch 2, pg 26, 32-45 Solar Neb Hyp Terrestrial planets are inner planets All plants move around sun in elliptical orbits We are terrestrial planet We are a tiny portion of an enormous universe Common theory - "Big Bang Theory" Nuclear fusion - combine nu...

Mod 2: Plate Tectonics Ch 2, pg 26, 32-45 Solar Neb Hyp Terrestrial planets are inner planets All plants move around sun in elliptical orbits We are terrestrial planet We are a tiny portion of an enormous universe Common theory - "Big Bang Theory" Nuclear fusion - combine nucleus - every time this happens, energy is released (lighter elements like hydrogen combine to form helium) Temp must reach close to 1mill celsius, unless that temp is reached, Nuc fusion won't happen. Heating - Temp increase Spinning - increase in velocity, gravitational and centrifugal force Flattening - protoplanetary disc, Solid, rocky planets formed in the hotter parts closer to the proptopplanetary disc, gas giants formed in the colder parts of the protoplanetary disk. Iron rich core of our planets goes back to the proto disk time. In the Beginning About 4.56 billion years ago = Age of earth, current theory ○ Geol - Use data to create story, needs imagination LOL Whole mantle of earth is hot, our central part is very high pressure, high temperature. Processes of planet formation created huge amounts of heat ○ Impact energy → energy of impact was transferred into the planet and is stored. ○ Decay of radioactive elements - Some elements cannot remain in their natural state, Potassium and iron can, uranium cant. Uranium decays until it becomes a new element. Uranium becomes stable (lead) it takes 20 steps and a huge amount of energy release. Gets transferred to thermal energy and is stored. U → PB (20 step process) ○ Gravitational energy → When it cools, heavy ones go to the center and lighter ones go to the surface ○ Differentiation into layers Early History of Earth First 100 million years after Earth's formation ○ Earth was molten with no distinct layers ○ Constant bombardment from meteorites ○ Collision with mars size object forming moon at ca.4.5 billion years ○ Object struck our planet, didn't leave bc of gravitational attraction, formed the moon and started orbiting around our planet. Just 1 of the current theories Earth Early Years After 100 million years… ○ Slow cool down ○ Differentiation into dense, metal rich core and lighter, silicate-bearing mantle, and crust  First solid crust formed from mantle at ca. 4.4 billion years All the elements like hydrogen, helium, magnesium etc are mixed together at a high temp, the temp cools down very slowly. Iron, titanium, start to sink towards the centre (core) of the big melting mass. The lighter elements such as potassium, sodium float to towards the surface Mantle - some layers Outer layer that we walk on is called the crust Crust → Mantle → Core. Crust is mostly light elements, heavier in the core. Earth History: TImetable 4.0 Ga ○ Large oceans, small continents/ early meteorite bombardment/ outgassing and secondary atmosphere 3.5Ga ○ Life (photosynthetic bacteria) 2.5 Ga ○ Growing contients/atmosphere I1% O2)/ plate tectonics 1.5 Ga ○ Large continents/ oxygen rich atmosphere What makes Earth Unique? Earth is the only planet that has life Earth has ○ Atmosphere: rich in oxygen ○ Hydrosphere: water as solid, liquid, or gas (vapour) ○ Biosphere: full of living organisms ○ Lithosphere: (Plate Tectonics): changing surface Q1: Earth is about _______ years old 30, 000 50 mill 3,500 million 13.5 billion 4.5 bill Differentiation of the Earth Differentiation: Layering of terrestrial planets based on chemical composition and density ○ Crust: outermost compositional layer Oceanic and continental crust → Continental crust is lighter, thicker, older than oceanic crust, esp below mountain belts Oceanic crust is darker in colour, continental crust is lighter in color and thicker and lighter and older. Below the oceans we have thinner, colder, denser crust. Thin, low-density and rocky ○ Mantle: middle compositional layer Rocky, intermediate density 83% of Earth's volume, 67% of Earth's mass  ○ Core: Innermost compositional layer High density and metallic 16% of earths volume, 32% of Earths mass Inner core: solid Outer core: liquid We rotate the sun, a little bit on the side which creates seasons. Rotational axis is a little on the side. Having a solid core contributes to the magnetic field. Protects us from the solar radiation, it protects us from meteorite impacts. Smaller meteorite impacts we barely notice, we notice the bigger ones. Layers of the Earth Physical Behaviour → Atmosphere (gas) Hydrosphere (liquid) Lithosphere (solid) Asthenosphere ("soft plastic") Mesosphere ("stiff plastic") , outer core (liquid) , inner core (solid) Density/Composition → Crust, mantle, core Seismic waves Terminology Lithosphere: Thin, rocky, rigid outer layer comprising crust, and small part of the upper mantle. ○ Mantle has several layers and the upper level is sold and then partially molten, then solid again. Lithosphere is broken into pieces that come together like a jigsaw puzzle. Asthenosphere: below lithosphere; layer is weak due to hot temp (near melting point) ○ Seismic waves will speed up in the upper most layer of the mantle, and then slow down in the asthenosphere. ○ Partially molten layer ○ If we didn't have this, no plate tectonics and we would have a water planet. But because plate tectonics and seismic waves, we have a solid planet. ○ Asthenosphere allows the plates to move. Isostasy: Relationship between lithosphere & asthenosphere ○ Lithosphere is essentially floating on the asthenosphere due to lower density -----End of Lecture-------- Sept 19 Lecture Divergent PLate Boundaries New oceanic crust forms new ocean boundaries Divergent plate boundary: A spreading zone where new crust is formed ○ Neighboring tectonic plates move in opposite direction ○ Constructive plate boundary - why we dont have oceanic crust older than 2 mill years Characteristics of divergent plates: ○ Creation of new oceanic crust ○ Associated with volcanism and earthquakes ○ Forming mid-oceanic ridges due to seafloor spreading ○ Neighbouring plates move apart from each other creating new oceanic crust on boundary due to volcanism ○ Mid oceanic ridge Convergent plate boundary: locations where lithospheric plates are moving towards one another 3 different types of convergent plate boundaries: ○ Continental - continental collision ○ Continental - oceanic collision ○ Oceanic - oceanic collision --older heavier will subduct ○ Subduction Characteristic of convergent plate boundaries: ○ Destruction of oceanic crust ○ Formation of mountain ranges or volcanic island arc ○ Earthquakes, volcanism and crustal deformation Collision of 2 continental curst creating mountain range and resulting often in earthquakes Closure of ocean that was once between these 2 plates Insert diagram Subduction Subduction → Geological process in which the edge of a lithospheric plate slides underneath the edge of an adjacent plate Subduction occurs between: ○ A continental and an oceanic crust: denser and thinner ○ An oceanic crust and another oceanic crust: Characteristics of subduction zones: ○ Formation of deep oceanic trenches, island arcs, and coastal mountain ranges made of volcanoes ○ Oceans get smaller and eventually disappear ○ Volcanism and earthquakes Examples of subduction zones: ○ Oceanic-continental crust: Andes, Cascadia ○ Oceanic-oceanic crust: Japan, Indonesia Sunduction: Oceanic- Continental Crust  Subduction of thinner, denser oceanic crust below thicker, less dense continental crust Result: Closure of ocean, mountain range of volcanoes and earthquakes Subduction: Oceanic-Oceanic Crust Aleutian Islands: Oceanic-Oceanic Collission Transform Plate Boundary Transform plate boundaries: Locations where two tectonic plates slide past one another ○ Movements are NOT smooth and can create high stress on rocks Results: ○ Shallow earthquakes ○ Deep faults and fractures on surface and rocks ○ NO volcanism Examples: ○ San Andreas fault, Western USA Movement of 2 tectonic plates against each other without diverging or converging Result (shallow) earthquakes, NO volcanism, deformation of rocks The Grand Unifying Theory Tectonic cycle: ○ Asthenosphere partially melts, rises up and creates new oceanic lithosphere along mid ocean ridges/spreading centres ○ Divergent plate boundaries ○ New oceanic lithosphere becomes older and denser as it gets older and farther from the ridge where it formed ○ Eventually oceanic lithosphere collides with another plate; whichever is colder and denser will be forced underneath and pulled into the mantle Subduction Convergent plate boundaries ○ When two plates collide and one plate is oceanic crust, denser (colder, older) plate goes beneath less-dense (warmer, younger) plate in subduction Oceanic plate beneath oceanic plate Volcanic island arc next to trench (Aleutian Islands of Alaska) Oceanic plate beneath continental plate Volcanic arc on continent edge next to trench (Cascade Range of Oregan, Washington, BC) ○ Plate tectonics requires time and perspective of millions and billions of years Plate movement may be 1cm/year → 75 cm in human lifetime 1cm/year is 10km in 1 million years ○ Plate tectonics requires size perspective of continents and plates ○ Time ○ Size How we Understand the Earth  Must think in terms of geologic time rather than human time Thousands, millions and billions of years In 1788, James Hutton introduced concept of geologic time ○ "No vestige of a beginning, no prospective of an end" ○ Everyday changes over millions of year add up to major results ○ Introduced term Uniformitarianism Uniformitarianism → Natural laws are uniform through time and space ○ "The present is the key to the past" ○ Physical and biological processes have observable effects today, this was also true in the past ○ Processes happening in and on earth today have operated in a similar manner throughout geologic time Currently modified actualism: Rates of earth processes can vary Study the present to the understand past nad make probabilistic forecast of the future Natural Disasters happened throughout geological time Module 3: Earthquakes Tuesday, Sept 24 What is an Earthquake? Earthquake: A sudden and violent shaking of the ground, sometimes causing great destruction, which results from shock waves generated by the movement of rock masses deep within the Earth, particularly near boundaries of tectonic plates. Caused by: ○ Volcanic activity ○ Meteorite impacts ○ Undersea landslides ○ Explosions of nuclear bombs ○ Most commonly, by movement of the earth across a fault ○ A crack with no movement is a joint, when there is a crack with movement we call it a fault ○ Heavy machinery in mines could cause minor earthquakes Earthquakes occur on all 3 plate boundary types: ○ Convergent: Ocean-continent collision Ocean-ocean collision Continent-continent collision ○ Transform ○ Divergent Fault: Fracture in the Earth across which two sides of a rock or plate move relative to each other Stresses: build up enough to cause rocks to fracture and shift, sending off waves of seismic energy, felt as earthquakes. Major Earthquakes between 1906-2012 Most earthquakes with magnitude >8.5: Along subduction zones = convergent plate boundaries are places where majority of very strong earthquakes occur Exception: Assam, Tibet = Continent-continent collision Earthquakes with high magnitudes caused by subduction = megathrust earthquakes Question 1: Earthquakes are most commonly caused by ____sudden earth movement along faults_______. Earthquakes & Faults  Earthquakes happen by sudden movement of strained blocks of Earth's crust along faults. ○ Fault surfaces are not smooth, movement of plate is constant - local stress increases ○ Plates move only a few cm/year against each other ○ Frictional resistance causes strain to build in rocks ○ Local stress > frictional resistance = release of strain energy Faults: A Description Fault Surface: planar surface along which movement or displacement occurs Footwall: fault block that underlies an inclined fault surface (ground where people stand) Hanging Wall: fault block that overlies an inclined fault surface Strike: direction of fault surface measured in the horizontal surface Dip: angle and direction of fault surface measure in a vertical surface Types of Faults Dominantly "vertical" movement ○ Dip-slip faults ○ Normal fault: hanging wall moves down (extension of pulling apart) ○ Reverse Fault ○ Thrust Fault ○ (a) Normal faults form during extension of the crust. The hanging wall moves DOWN. Dom vertical movement ○ Dip-slip ○ Normal fault ○ Reverse fault: hanging wall moves up ○ Thrust ○ (b) reverse faults form during shortening of the crust; the hanging wall moves UP and the fault is steep. ○ Thrust fault: reverse fault with shallow dip angle Dip-Slip Faults: Normal Fault Dominant force is extensional (pulling apart) - hanging wall moves down relative to footwall Zone of omission results: layers are missing in a vertical bore Found at locations of seafloor spreading and where continents are pulling apart Hanging block down = normal fault caused by extension divergent Dip-Slip Faults: Reverse Fault Dominant force is compressional Reverse fault occurs when hanging wall moves up relative to footwall Zone of repetition results: Layers are repeated in a vertical borehole Occur where plates converge in continental collision or subduction If dip of fault