Exam 3, part 2 | GEOS 1004 - Physical Geology, Quizzes of Geology

Download Exam 3, part 2 | GEOS 1004 - Physical Geology and more Quizzes Geology in PDF only on Docsity! TERM 1 Earthquakes DEFINITION 1 a shaking of the ground produced by the rapid release of energy most commonly associated with slip along fault surface TERM 2 The Elastic Rebound Hypothesis DEFINITION 2 As stress is applied to the fault, the rocks on either side of the fault deform elastically. Critical stress level, slip on the fault occurs and the two blocks or rock slid past each other, relieving the stress on the fault. Stress removed...the rock on either side of the fault bounces back to its original shape, releasing elastic strain energy as shock waves. TERM 3 Seismic Waves DEFINITION 3 pulses of energy released during an earthquake, slower, rope analogy... waves move up and down ***cannot move through liquid Two groups of seismic waves: surface waves and body waves TERM 4 Focus DEFINITION 4 the point within the earth from which seismic waves originate TERM 5 Epicenter DEFINITION 5 the point on the Earth's surface directly about the focus of an earthquake TERM 6 Surface Waves DEFINITION 6 Seismic waves that travel on the Earth's surface spreading outwards from the epicenter "Idaho example" TERM 7 Body waves DEFINITION 7 Seismic waves that travel through the Earth's interior, spreading outwards from the focus in all directions "big waves" Two main types of body waves: P waves and S waves TERM 8 P wave DEFINITION 8 compressional wave in which rock vibrates parallel to the direction of wave propagation move back and forth like a slink, faster speeds of 4 to 7 kilometers per second, propagate through solids and liquids *** first to arrive at a recording station following an earthquake TERM 9 S Wave DEFINITION 9 propagated by a shearing motion, the rock vibrates perpendicular to the direction of wave propagation rope example, move up and down, slower speeds of 2 to 5 kilometers per second, arrives after the arrival of the P wave 'S' for secondary. can only propagate through solids*** TERM 10 How do we know the outer part of earth's core is liquid? DEFINITION 10 S waves cannot travel through liquid, can only propagate through solids TERM 21 Richter Scale DEFINITION 21 logarithmic-difference between two whole numbers on the scale means an increase of 10 times in the amplitude of the earth's vibrations recorded on the seismogram higher numbers..larger earthquakes, largest measured so far is 8.6 tenfold increase in the size of the earth's vibrations is caused by an increase of about 31.5 times in terms of energy released TERM 22 Examples for Mid Term 3 DEFINITION 22 increases by 31.5 every one whole number... magnitude 5 releases 31.5 releases 31.5 times more energy then a quake of magnitude 4 magnitude 6 (31.5x31.5) is almost 1000 times more powerful in terms of energy released than a magnitude 4 quake magnitude 8 is 985,000 times more powerful in terms of energy released than a magnitude 4 quake TERM 23 Intensity DEFINITION 23 A measure of an earthquake's effect on people and buildings (what kind of damage has occurred) TERM 24 Modified Mercalli Scale DEFINITION 24 measuring the intensity of an earthquake and the intensities are expressed as Roman numerals ranging from I to XII. earthquake damage is generally greatest close to the epicenter and decreases with distance from the epicenter TERM 25 Isoseismal lines DEFINITION 25 lines connecting values of equal intensity after an earthquake occurs, intensity values can, for populated areas be plotted on a map (isoseismal map) -only draw maps on land -only draw maps when there is damage iso- means the same TERM 26 New madrid earthquake 1811 DEFINITION 26 plates come together or where mountains-> where most earthquakes occur TERM 27 Earthquakes and Benioff Zones DEFINITION 27 deep earthquakes.. benioff zones: incline zone of earthquakes that dip under a continent, steep oceanic trench TERM 28 Rate of seismic waves DEFINITION 28 Seismic waves travel through fast when material is colder Seismic waves travel slowly when material is warmer TERM 29 The Crust DEFINITION 29 the outer layer of rock which forms a think skin on the Earth's surface TERM 30 The Mantle DEFINITION 30 a thick shell of rock that separates the crust from the core below TERM 31 The Core DEFINITION 31 the central zone of the Earth which is probably metallic and the source of the Earth's magnetic field TERM 32 inge Lehmann DEFINITION 32 She made important contributions to our understanding of the Earth's interior...due to her that the inner part of the core is a solid TERM 33 Velocity of Seismic Waves DEFINITION 33 Speed of seismic waves is proportional to the rigidity of the rocks through which they pass Travel most rapidly in rigid materials which elastically spring back to their original shapes when the stress is removed; the more rigid the rock, the greater the velocity at which the seismic wave travels. lowest speeds- granite, then basalt, then ultramafic TERM 34 Where is the earth's crust thinnest beneath? DEFINITION 34 Thinner beneath the oceans than beneath the continents Seismic waves travel faster in oceanic crust than in continental crust TERM 35 Oceanic crust DEFINITION 35 P waves travel at 7 km per second, speed at which they pass through basalt in the laboratory TERM 46 Ocean Trench DEFINITION 46 narrow, deep trough parallel to the edge of a continent or an island arc (a curved line of islands) TERM 47 Mid- oceanic Ridges DEFINITION 47 large linear mountain ranges, rise from the depths of every ocean basin, and are interconnected in a worldwide network over 60,000 km long Atlantic ocean the ridge is at the centre of the basin Pacific ocean, the ridge is near the eastern margin TERM 48 What is the deepest trench in the world? DEFINITION 48 The Mariana Trench of the western Pacific Ocean 11,035 meters or 36,204 feet below sea level TERM 49 Rift Valley DEFINITION 49 large crack apparently of tensional origin runs down the crest of the ridges, generally 1 to 2 km deep and several kilometers wide TERM 50 Fracture zones DEFINITION 50 major lines of weakness in the earth's crust that cross the mid-oceanic ridges at right angles zones which separate the ridge into segments are often marked by steep cliffs up to 2 or 3 kilometers high, many extend for thousands of kilometers across the ocean floor TERM 51 Geological Activity in Mid-Ocean ridges DEFINITION 51 high heat flow on the crest of the ridge basalt eruption in and near the rift valley shallow focus earthquakes TERM 52 Continental Drift DEFINITION 52 concept that the continents are not fixed in position but move over the earth's surface. Put forward by German meteorologist Alfred Wegener TERM 53 Pangea DEFINITION 53 'all lands' Wegener's theory that the continents could have originally fitted together to form a supercontinent TERM 54 Panthalassa DEFINITION 54 the single ocean that surrounded Pangea TERM 55 What are the two sub-continents of Pangea? DEFINITION 55 Laurasia and Gondwanaland TERM 56 Laurasia DEFINITION 56 made up of present day North America and Europe- Asia TERM 57 Gondwanaland DEFINITION 57 made up of present day South America, Africa, India, Antarctica and Australia TERM 58 Wegener's four main lines of evidence for continental drift and former existence of Pangea DEFINITION 58 1. fit of the continents 2. fossil evidence 3. rock type and structural similarity 4. palaeoclimatic evidence 5. palaeomagnetism (not discovered until after his death) TERM 59 Fit of the continents DEFINITION 59 Similarity in shape of the Atlantic coastlines of South America and Africa TERM 60 Fossil evidence DEFINITION 60 organisms were restricted in geographical distribution, but appeared in two or more areas that are presently separated by oceans