FIGURE 2.12 Generalized geologic map of southern California. Half-arrows indicat
ID: 295951 • Letter: F
Question
FIGURE 2.12 Generalized geologic map of southern California. Half-arrows indicate relative motions along the San Andreas Fault. The fault is also a boundary between two of Earth's lithospheric plates. The relative motion of the Pacific Plate (under the Pacific Ocean) is northwest. The North American Plate is located east of the fault and is moving relatively southeast. CALIFORNIA San PACIFIC OCEAN Q Quatemary ? socene Santa Barbera Cretaceous Los Angeles 100 200 m San Andreas Fault Hazards b. You can estimate the average annual rate of movement along the San Andreas Fault by mea- suring how much the Late Miocene rocks have been offset by the fault and by assuming that these rocks began separating soon after they formed. What is the average annual rate of fault movement in centimeters per year (cm/yr)? c. The average yearly rate of movement on the San Andreas Fault is very small. Does this mean that the residents of southerm California have nothing to worry about from this fault? Explain d. An average movement of about 5 m (16 ft) along the San Andreas Fault was associated with the devastating 1906 San Francisco earthquake that killed people and destroyed properties. Assuming that all displacement along the fault was produced by Earth motions of this magnitude, how often must such earthquakes have occurred in order to account for the total displacement? Study the geologic map of southen California in Figure 2.12, showing the position of the famous San Andreas Fault. The east side of this fault is rocks of the North American lithospheric plate. The west side of the fault is the Pacific lithospheric plate, which is moving northwest. It is well known to all who live in southern California that plate motions along the fault cause frequent earthquakes that place at risk humans and their properties Question 19. The two bodies of Late Miocene rocks (about 25 million years old) located along either side of the San Andreas Fault (Figure 2.12) were one body of rock that has been separated by motions along the fault. Note that arrows have been placed along the sides of the fault to show the relative sense of movement. a. The San Andreas Fault is what kind of plateExplanation / Answer
a) The San Andreas fault is a Transform boundary. this is clearly shown in the map , with the help of the two arrows.the two arrows slide eachother.There are 3 types of plate boundaries 1) convergent boundary; where two plates come together; 2) divergent boundary, when two plates move away from eachother, 3) and transform boundary when two plates slide eachother, like in San Andes.
b)San Andes fault is 1300 km long and extends 25 km in depth.and has north west -- south east trend.The average rate of movement along san Andes fault is between 2.5cm per years.
c)San Andes Fault experiences tactonic movements every year ,although these are small shifts but they are dangerous ,as it causes earthquakes.The 1906 earthquake was accompanied by nearly 300 miles of surface rupture along the San Andes between San Juan Bautista and shelter cove. The movements are so jurky and disruptive in nature,
Earthquake is serious problem, as it cause alot of distruction.There are more faults formed due to small tremors it is a serious as it might lead to a serious earthquake.there were nearly 200 small earthquakes that shook southern califonia.
Being on the seaside any serious earthquake can also cause a Tsunami. which is ver devasting in nature.
It can also cause valcanoes,Continous movement of the plates can creat deep faults which can lead to volcanous. volcanous tend to occur in earthquaks prone areas.
In san Andes due to faults creation the area has also witnessed the release of helium gas. which is very dangerous for humans.
plate movements has lead to redistribution of land masses and long term effect on climate.these effects may result these effects may result from land mass drifting into different latitudes or from sea beds being pushed upwards to form fold mountains.
Rain water sweeping into the cracks and faults of the plates can cause earthquakes and valcanoes.
all these effects the life of people and distroy life and properties. small earthquakes can lead to sever earthquakes which can devast many lives and properties.
d)Along the earth"s plate boundaries , such as the san Andreas fault segments exist where no large earthquakes have occured for a long time . Scientists term these segments as seismic gaps, and in general have been successful in forecasting the time when some of the seisemic gaps will produce large earthquakes. Geologic studies show that over past 1400 to 1500 years large earthquakes have occurred at about 150 year intervals on the sourthern San Andreas fault .
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.