| A | B |
|---|
| chemical composition of Earth | 3 layers based on chemical composition: crust, mantle, core |
| crust | thinnest, least dense layer; less than 1% of mass |
| 2 types of crust | continental (thicker, less dense); oceanic (thinner, more dense) |
| mantle | middle chemical layer of Earth; contains most (67%) of Earth's mass |
| core | central, most dense chemical layer; made mostly of iron; 33% of Earth's mass |
| physical structure of Earth | 5 physical layers: lithoshpere, asthenosphere, mesosphere, inner core, outer core |
| lithosphere | outermost, rigid layer including crust and upper mantle; divided into tectonic plates |
| asthenoshpere | soft layer beneath lithoshpere on which tectonic plates "float" |
| mesoshpere | strong, lower part of mantle between asthenosphere and outer core |
| outer core | liquid layer of core between mesosphere and inner core |
| inner core | solid, central part of core |
| tectonic plates | blocks of lithoshere; fit together like jigsaw puzzle; float atop asthenosphere; bump and grind into or past one another or pull apart |
| seismic waves | generated by earthquakes and used to "map" structure of Earth's interior |
| seismograph | instrument used by geologists to study seismic waves |
| Alfred Wegener | created theory of continental drift in early 1900s; not accepted by many at the time |
| Theory of continental drift | theory that continents can drift apart from one another and have done so in past; explains puzzle like "fit" of continents |
| Pangaea | single huge land mass 245 million years ago that split apart to become today's continents |
| Panthalassa | enormous sea that surrounded Pangaea |
| Laurasia | northern piece of what had been Pangaea after it split in two |
| Gondwana | southern part of Pangaea after it split in two |
| Mid-Atlantic Ridge | chain of submerged mountains running through center of Atlantic Ocean |
| sea-floor spreading | process by which new oceanic lithosphere is created as sea floor plates spread apart (magma fills void) |
| magnetic reversal | north and south magnetic poles have reversed position many times in past, as evidenced by directional bands of magnetic minerals |
| plate tectonics | theory that Eath's lithosphere is divided into tectonic plates that move around on top of asthenosphere; explains both continental drift and sea floor spreading |
| 3 driving forces of plate movement | ridge push, slab pull, convection |
| ridge push | process by which oceanic plate slides down lithosphere/asthenosphere boundary |
| slab pull | process by which more dense oceanic plate slides into asthenosphere, dragging rest of tectonic plate with it |
| convection | process by which convecting material drages tectonic plates sideways (hot, less dense material rises; cooler material sinks) |
| 3 main types of tectonic plate boundaries | convergent, divergent, transform |
| convergent boundaries | boundaries where 2 plates push into one another (compression) |
| subduction zone | where one plate slides under another (magma can rise here) |
| divergent boundaries | boundaries where two plates move away from one another (tension); as plates move apart, magma fills gap forming new lithoshpere |
| transform boundaries | boundaries where two plates slide past one another (can cause earthquakes) |
| San Andreas Fault | fault representing transform boundary between North American and Pacific plates which remains stationary for years but occasionally shift several meters, causing earthquakes |
| Global Positioning System (GPS) | network of satellites that can be used to measure tectonic plate movement |
| Deformation | process by which shape of rock changes due to stress |
| compression | stress when object is squeezed (such as at convergent boundaries) |
| tension | stress when an object is stretched (such as at divergent boundaries) |
| folding | bending of rock due to stress; can result in anticlines, synclines or monoclines |
| anticlines | upward arching folds in rock (dome or bump shape) |
| synclines | downward arching folds in rock (trough shape) |
| monocline | rock layers folded so that ends of fold are horizontal to one another |
| fault | break in body of rock along which one block slides past other |
| fault blocks | blocks of rock on either side of fault |
| hanging wall | fault block in which top extends beyond bottom |
| footwall | fault block in which bottom extends beyond top |
| 3 types of faults | normal, reverse, strike-slip |
| normal fault | fault in which hanging wall slides down relative to footwall (tension) |
| reverse fault | fault in which hanging wall moves up relative to footwall (compression) |
| strike slip fault | fault in which fault blocks slide past one another horizontally |
| 3 common types of mountains | folded, fault-block, volcanic |
| folded mountains | mountains created when convergent forces compress rock layers, pushing them upward (Appalachians, Alps, Himalayas) |
| fault-block mountains | mountains in which tension (divergence) causes normal faults with large blocks dropping relative to others, forming jagged peaks (Grand Tetons) |
| volcanic mountains | mountains that occur where oceanic crust sinks at subduction zones at convergent boundaries (Hawaiian Islands) |
| Ring of Fire | ring of volcanoes surrounding Pacific Plate |
| uplift | rising of crust to higher elevations |
| subsidence | sinking of crust to lower elevations |
| rift zones | areas where divergent plates are pulled apart (East African Rift) |
