| A | B |
|---|
| What are tectonic plates? | fragments of the lithosphere |
| What is hotter asthenosphere or lithosphere | asthenosphere hotter than 1280 degrees C and that the temp where rock begins to flow (litho is cooler and below the 1280 degrees C) |
| Lithosphere BENDS when loaded | elastic |
| Asthenosphere FLOWS when loaded | plastic |
| Principle of buoyancy | floating solids displace liquid = to their mass |
| Lithospheric plates sink where.... | into the asthenosphere |
| What floats higher continental or oceanic plates? | continental floats higher and oceanic floats lower |
| About how high are the continents above the ocean floor? | 4.5 km |
| Why do continents stand higher than ocean basins? | the continental crust is light 2.7g/cm3 |
| thin oceanic crust is pretty heavy | 3.0g/cm3 |
| what is the thickness of lithosphere | 150 km thick |
| old oceanic lithosphere is how thick | ~100 km |
| newer oceanic lithosphere | 7-10 km in thickness---takes some time to thicken up |
| What part of earth's layer is the lithosphere? | it is the crust and upper part of mantle |
| temperature divides up the litho from the asthenos | see picture in binder |
| How many plates is the lithosphere fragmented into? | 15-20 (plates interact on boundaries) |
| How are boundaries identified? | by concentrations of earthquakes |
| Plate INTERIORS are earthquake free; it is the boundaries that are identified by earthquakes | xxxx |
| The ring of fire | see diagram |
| continental margins | ocean/continent boundaries |
| active margins | located near plate boundaries |
| passive margins | NOT near plate boundaries |
| THREE TYPES OF PLATE BOUNDARIES | you will need to know them and they are on the next 3 cards |
| divergent boundary | sea floor spreading, plates move away from each other |
| convergent boundary | plates move toward each other; subduction |
| transform boundary | plates move side by side |
| other names for divergent boundaries | moving away from each other so "spreading boundaries" mid ocean ridge is an example |
| learn process of mid ocean ridges forming | SEE DIAGRAM - best way to learn how the magma forms and filld the chamber |
| what is the total width of mid ocean ridges? | ~1500 km |
| Where is the Mid Atlantic Ridge? | it snakes north to south throught the ENTIRE Atlantic Ocean |
| Facts on Mid Atlantic Ridge | 500 m deep, 10 km wide; symmetic and site of eruptions |
| what are black smokers? | found in some mid ocean ridges and it is water entering fractured rocks heated by magma and the hot water dissolves the minerals and cycles back |
| Atlantic mid ocean ridge | oldest ocean floor near passive continental margins |
| forming lithospheric mantle | asthenosphere cools when it pasts the 1280 degree celsius and is no longer in aesthenos and is now part of lithosphere; thickens, cools, densifies |
| thck mantle | called "ballast" see picture |
| CONVERGENT boundary | plates move toward each other |
| convergent boundary | also called convergent margin |
| process of subduction - convergent boundary | old ocean lithosphere (more than 10 million years old) more dense than the mantle |
| what is the Wadati-Benioff zone? | it's the zone referring to earthquakes associated with subduction |
| At what rate do plates descent (go down) because of subduction? | plates descend 10-15km per year |
| Earthquakes and subduction | earthquakes are associated with subduction up to 660 km deep |
| Oldest ocean floor (because of subduction)? | 200 million years old |
| oldest continental crust because of subduction? | 3.8 billion years old |
| features of subduction | plates melt making magma, magma rises leading to volcanic arcs |
| Why can't continental crust be subducted? | it is too buoyant |
| Why did Japanese earthquake happen March 11? (mom's bday) | slip between Pacific and North American plates - a subduction zone |
| transform boundary | plates move alongside each other |
| transfoirm boundary | plates grid past each other in horizontal motion |
| MOST transform faults occur where? | underwater between oceanic plates |
| San Adreas fault is is an example of? | transform boundary |
| What are triple junctions? | places where three plate boundaries coincide |
| what are hot spots? | volcanic plumes independent of tectonic plates |
| theory of hot spots | they formed from extinct volcanoes and volcanic islands |
| hot spot volcanoes make seamounts | xxx |
| continental rifting | Arabian plate is rifting from African plate |
| continental rifting | East African Rift - thin crust, volcanoes |
| plate collision | can be two continents or a continent and an island arc |
| What drives plate motion? | ridge "push" force OR slab "pull" force gravity pulls the subducting plate downwards |
| What is the key to understanding geology? | plate tectonics |
| the interior and surface of Earth are in constant motion | xxxx |
| Plate tectonics explains | earthquakes, volcanoes, and continental drift |
