GEOL100C

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Fullerton College *

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100

Subject

Geology

Date

Oct 30, 2023

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pdf

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Uploaded by eyeaye

Study Guide For Test 4 Geologic Time • Understand how geologists use fossils to help determine the age of rocks. • From a diagram showing geologic rocks and structures, be able to put these features in order from oldest to youngest: • o Law of Superposition o Law of Horizontality o Law of Cross-Cutting •

Unconformity o Nonconformity o Angular Unconformity o Disconformity •

Law of Faunal Succession • • o

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o Index Fossils • o Plate Tectonics • Continental Crust • Oceanic Crust •

• • Convergent Boundary • Divergent Boundary • Transform Boundary • • Hot Spot- A hot spot is an area on Earth over a mantle plume or an area under the rocky outer layer of Earth, called the crust, where magma is hotter than surrounding magma . The magma plume causes melting and thinning of the rocky crust and widespread volcanic activity Subduction- the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.

Tectonic plates- There are major, minor and micro tectonic plates. There are seven major plates: African, Antarctic, Eurasian, Indo-Australian, North American, Pacific and South American . The Hawaiian Islands were created by the Pacific Plate, which is the world's largest plate at 39,768,522 square miles. • Understand how tectonic plate movement speed is calculated distance/time. Use the formula (island distance from hotspot ÷ island age ) to calculate the rate of movement for 1. each island in the chart, then multiply by . 1 to convert from kilometers per million years to centimeters per year. • Understand what happens to crust when it is over a hot spot and what happens to it after it moves off of the hot spot • What happens to a hot spot as the crust moves over it? • A hot spot is an intensely hot area in the mantle below Earth's crust. The heat that fuels the hot spot comes from very deep in the planet. This heat causes the mantle in that region to melt. The molten magma rises up and breaks through the crust to form a volcano . • What happens when a hot spot volcano moves off the hot spot?

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• A volcano above a hot spot does not erupt forever. Attached to the tectonic plate below, the volcano moves and is eventually cut off from the hot spot. Without any source of heat, the volcano becomes extinct and cools . This cooling causes the rock of the volcano and the tectonic plate to become more dense. • Compare and contrast all 7 types of plate boundaries • Convergent boundaries: where two plates are colliding. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. ... • Divergent boundaries – where two plates are moving apart. ... • Transform boundaries – where plates slide passed each other Convergence Boundary: Convergence boundary created when two plates move towards each other and one plate undergoes to another plate leads to the destruction of crust. The following are three types of convergence boundary: § Continent-continent plates convergence § Continent-Ocean plates convergence § Ocean-Ocean convergence Continent-continent convergence: The following are activities: § Fold mountain is created. § No subduction zone. § Earthquake may originate § No volcanoes activities Continent ocean convergence: The following are activities: § Fold mountain § Subduction zone formed as ocean plate is generally heavy and undergoes to continents plate § Volcanoes formed in the land. § Earthquake occurs. § Trenches are created at the meeting zone of ocean and continent. Ocean-Ocean convergence: The following are activities: § Subduction Zone formed § The occurrence of volcanoes in the ocean. § Earthquakes originated Divergence boundary: In divergence boundary, two plates move away from each other. A new crust is created in divergence boundaries. There are two types of divergence boundary: § Continetal-continetal divergence § Oceanic-oceanic divergence Continetal-continetal divergence The following are activities:

§ Rift Valley is created. § Examples, African rift valley is examples of continent-continent divergence. Oceanic-oceanic divergence The following are activities: § The mid-ocean ridge is created in the boundary region. § Volcanoes activities in the mid-oceanic region § Earthquakes originated The transverse boundaries: The transverse boundary is created when the plate slides each other without submergence and the creation of any plates. Alpine fault in New Zealand is an example of the transverse boundary. The similarity in three boundaries: § Earthquake is generated in all types of plate boundaries. § Pacific ring of fire is the result of all three types of plate boundaries that is Ocean- ocean convergence, Ocean-ocean divergence, Ocean-ocean transverse. Earthquake Hazards and Human Risks Understand the time-travel curve and how to determine the distance from an earthquake epicenter to a seismic station • To figure out just where that earthquake happened, you need recordings from seismic stations in other places. While earthquake locations are normally done with a computer that can quickly determine the paths of seismic waves through the Earth to many seismic stations, you can get a good estimate of an earthquake location using a map, a ruler, a pencil, and a compass for drawing circles on the map. • Here are examples of a seismograms from different places in North America that recorded the same earthquake. Distances from the stations to the earthquake are estimated from the difference between P and S wave arrival times:

• • Measure the distance between the first P wave and the first S wave. In this case, the first P and S waves are 24 seconds apart. • Find the point for 24 seconds on the left side of the chart of simplified S and P travel time curves and mark that point. According to the chart, this earthquake's epicenter was 215 kilometers away. • Measure the amplitude of the strongest wave. The amplitude is the height (on paper) of the strongest wave. On this seismogram, the amplitude is 23 millimeters. Find 23 millimeters on the right side of the chart and mark that point. • Place a ruler (or straight edge) on the chart between the points you marked for the distance to the epicenter and the amplitude. The point where your ruler crosses the middle line on the chart marks the magnitude (strength) of the earthquake. This earthquake had a magnitude of 5.0. •

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Understand how to plot the epicenter of an earthquake. • Focus • Epicenter • Earthquakes originate at a point called the focus (plural foci). From this point, energy travels outward in different types of waves. The place on the Earth’s surface directly above the focus is called the epicenter • Body wave • P-wave • S-wave • Surface wave • As an earthquake occurs, two different types of waves are produced; body waves , so termed because they travel through the body of the Earth, and surface waves that travel along the Earth’s surface (Figure 13.4). There are two types of body waves. P- waves , or primary waves, are compressional waves that move back and forth, similar to the action of an accordion. As the wave passes, the atoms in the material it is travelling through are being compressed and stretched. Movement is compressional parallel to the direction of wave propagation, which makes P-waves the fastest of the seismic waves. These waves can travel through solids, liquids, and gases, because all materials can be compressed to some degree. S-waves , or sec- ondary waves, are shear waves that move material in a direction perpendicular to the direction of travel. S-waves can only travel through solids, and are slower than P-waves. • Love-wave • Rayleigh-wave • Surface waves are slower than body waves, and tend to produce more roll- ing sensations to those experiencing an earthquake, similar to being in a boat on the sea. Because surface waves are located at the ground’s surfacewhere humans (and their structures) are lo- cated, and because they move so slowly, which bunches them up and increas- es their amplitude, they are the most damaging of seismic waves. Love waves are the faster surface waves, and they move material back and forth in a hor- izontal plane that is perpendicular to the direction of wave travel (see Figure 13.4). Buildings do not handle this type of movement well, and Love waves may be responsible for considerable damage

to structures. Rayleigh waves make the Earth’s surface move in an elliptical mo- tion, similar to the movement in a sea wave. This results in ground movement that is up and down and side-to-side. • Seismogram • The study of earthquakes, called seismology , began to take off with the development of instruments that can detect earthquakes; this instrument, called a seismograph , can measure the slightest of Earth’s vibrations (Figure 13.5). A typ- ical seismograph consists of a mass suspended on a string from a frame that moves as the Earth’s surface moves. A rotating drum is attached to the frame, and a pen attached to the mass, so that the relative motion is recorded in a seismogram . Previous