DOCSLIB.ORG

Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, Beta, Corner Magnitude, Coupled Lithosphere Thickness, A

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, Beta, Corner Magnitude, Coupled Lithosphere Thickness, A Bulletin of the Seismological Society of America, Vol. 94, No. 6, pp. 2380–2399, December 2004 E Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, Beta, Corner Magnitude, Coupled Lithosphere Thickness, and Coupling in Seven Tectonic Settings by Peter Bird and Yan Y. Kagan Abstract A new plate model is used to analyze the mean seismicities of seven types of plate boundary (CRB, continental rift boundary; CTF, continental transform fault; CCB, continental convergent boundary; OSR, oceanic spreading ridge; OTF, oceanic transform fault; OCB, oceanic convergent boundary; SUB, subduction zone). We compare the platelike (nonorogen) regions of model PB2002 (Bird, 2003) with the centroid moment tensor (CMT) catalog to select apparent boundary half-widths and then assign 95% of shallow earthquakes to one of these settings. A tapered Gutenberg-Richter model of the frequency/moment relation is fit to the subcatalog for each setting by maximum likelihood. Best-fitting b values range from 0.53 to 0.92, but all 95% confidence ranges are consistent with a common value of 0.61– 0.66. To better determine some corner magnitudes we expand the subcatalogs by (1) inclusion of orogens and (2) inclusion of years 1900–1975 from the catalog of Pacheco and Sykes (1992). Combining both earthquake statistics and the plate- tectonic constraint on moment rate, corner magnitudes include the following: CRB, 0.48ם 0.52ם 0.21ם 0.47ם 0.76ם -Cou . 0.46מand SUB, 9.58 ; 0.22מOCB, 8.04 0.39מCCB,; 8.46 0.21מCTF,; 8.01 ;0.26מ7.64 7.0ם ,CTF 1.4מpled lithosphere thicknesses are found to be the following: CRB,;3.0 ?ם 0.13ם ?ם 11ם ;for strike slip 0.21מfor normal faulting and 0.40 0.09מOSR, 0.13 11מCCB,; 18 ; 4מ8.6 1.1ם 1.1ם ?ם ,at low, medium, and high velocities; OCB 0.5מand 1.6 , 0.5מ1.8 , 7.3מOTF,13 ?ם 13.7ם In general, high coupling of subduction and continental . 10.8מand SUB, 18.0 ; 2.3מ3.8 plate boundaries suggests that here all seismic gaps are dangerous unless proven to be creeping. In general, low coupling within oceanic lithosphere suggests a different model of isolated seismic fault patches surrounded by large seismic gaps that may be permanent. Online Material: Global seismic subcatalogs of shallow earthquakes. Introduction Since the introduction of plate-tectonic theory four de- (e.g., Cascadia and South Chile trenches) and many centu- cades ago, it has been widely expected to provide a basis for ries in plate interiors. quantitative prediction of long-term-average seismicity and The plate model of Bird (2003) was specifically con- seismic hazard. This promise has not been fully realized be- structed to address the first two problems. Instead of 14 cause of several problems: (1) Early models with 12–14 plates, it has 52, allowing most of the complexity of the plates gave seriously oversimplified kinematic predictions in Pacific margin to be described. It explicitly excludes the some of the most seismically active areas (e.g., the southwest most complex regions as “orogens.” This new global model Pacific). (2) Some regions are so complex that it is doubtful allows the third problem to be addressed by use of the er- whether any rigid-plate model can adequately describe them godic assumption: for studies of globally uncorrelated be- (e.g., Tibet Plateau and North Fiji Basin). (3) It is not re- havior, data collected widely in space can substitute for local solved whether seismic coupling is nearly perfect, or highly data collected over long times. By merging the behavior of variable, within the cold frictional seismogenic layer of the all subduction zones or all continental transform faults lithosphere. This question is difficult to answer in any re- worldwide for a century, we may have enough information gional study because the instrumental seismic record only to extract their average seismicity properties with confidence covers one century, whereas there are good indications of limits that are small enough to be useful. seismic cycles lasting five centuries in some plate boundaries The model of Bird (2003) also explicitly classifies each 2380 Plate-Tectonic Analysis of Shallow Seismicity 2381 short plate-boundary step (interval) as belonging to one of www.seismology.harvard.edu/projects/CMT/. This catalog seven classes: continental rift boundary (CRB), continental begins 1 January 1977, and through the cutoff date for this transform fault (CTF), continental convergent boundary study (30 September 2002) it contains 15,015 events with (CCB), oceanic spreading ridge (OSR), oceanic transform centroid depth Յ70 km. Nuclear tests and other explosions fault (OTF), oceanic convergent boundary (OCB), and sub- are excluded from CMT. The threshold moment for com- ഡ 17 ן ס duction zone (SUB). We first consider the reasons why earth- pleteness is Mt 3.5 10 Nm(mt 5.66) overall; for quake epicenters do not lie precisely on plate boundaries and specific years and/or regions, the threshold is sometimes adopt a rule for selecting the apparent seismic half-widths lower (Kagan, 2003). Each solution includes a moment ten- of plate-boundaries. Then, we use a probabilistic approach sor; we make use of the orientations of the principal axes to match shallow earthquakes with particular plate-boundary and the scalar moment but do not consider possible non- segments by searching for the best match between earth- double-couple source components. Ekstro¨m and Nettles quake properties. Then, we collect the earthquakes into eight (1997) extended the CMT catalog by finding moment tensors subcatalogs, corresponding to seven plate-boundary types of 108 large events (including 98 shallow events) in 1976. 18 ן ഡ and plate interiors. We analyze each subcatalog by maxi- If their threshold magnitude is estimated as Mt 3 10 ഡ mum-likelihood methods to determine the parameters of its Nm(mt 6.28) for shallow events, then there are 59 shal- tapered Gutenberg-Richter frequency/moment relation (Ka- low earthquakes in the complete part. gan, 2002a). Finally, we integrate these distributions to es- There are at least three valuable catalogs of the earlier timate the long-term-average moment rate for each class and years of the twentieth century (1900–1975): Pacheco and compare them with plate tectonic model predictions of the Sykes (1992), Triep and Sykes (1997), and Engdahl and Vil- line integrals of relative velocity. From the ratios, we deter- lasen˜or (2002). The first catalog is most convenient for our mine coupled lithosphere thicknesses for each type of plate study because Pacheco and Sykes collected moment deter- boundary. minations from the literature, when available, and scaled 20- sec surface-wave magnitudes to estimated moments for other Data Sets events. Saturation of surface-wave magnitudes should not greatly affect this catalog, since most of the larger events The plate-tectonic model used in this study is named (all but two of the m Ͼ 8.0 events) have independently de- PB2002. Bird (2003) described its construction and format, termined moments. Where multiple-moment estimates were which included explicit mapping of boundary locations. In available, we accept their selection. In addition, the Pacheco addition to the 14 large plates of the NUVEL-1 model and Sykes (1992) catalog provides limited mechanism in- (DeMets et al., 1990), it includes 38 small plates docu- formation (generic type) for 41% of the events, which is mented with recent geodetic, bathymetric, and/or seismic useful in assigning events to the correct tectonic setting. It data. Euler poles are tabulated for estimation of present rela- lists 598 shallow events during 1900–1975 and is complete Ն tive velocities. Model PB2002 does not claim to achieve a for shallow earthquakes with surface-wave magnitude Ms complete description of kinematics on the Earth. Instead, it 7. One peculiarity of the Pacheco and Sykes (1992) catalog formally designates 13 “orogen” regions in which the plate is that it lists the two largest earthquakes of the twentieth model is known to be inaccurate, either due to very many century as occurring only 1 min apart at virtually the same small plates or to nonplatelike behavior. In most phases of location: 19:10 versus 19:11 on 22 May 1960, at 38.05/ and 9.49 ס this study, seismicity of these orogens will be excluded. 38.20Њ S, 73.34/73.50Њ W, 32 km depth, with m However, it will be considered in some cases where we seek 9.64, respectively. The first event apparently refers to the to maximize the sizes of subcatalogs of large earthquakes. low-frequency precursor detected by both Kanamori and Ci- Earthquake sizes are best characterized by scalar mo- par (1974) and Cifuentes and Silver (1989) 15–19 min be- ment M, but moment magnitude m is also a popular scale. fore the main shock. Such fault-creep events (also called In this project, we used the conversion “slow” or “silent” earthquakes) are rarely detected unless they generate tsunamis or precede famous main shocks. מ ס m (2/3)(log10 (M) 9.05) (1) Since it is not possible to include all fault-creep events down to the same moment threshold used for earthquakes, we pre- of Hanks and Kanamori (1979). There is confusion because fer to drop this one slow precursor event from the catalog. some later authors have used slightly different values of the We note that Engdahl and Villasen˜or (2002) treated this constant (Kagan, 2003). Magnitudes quoted in this article event in the same way. (as a convenience for readers) should be converted to scalar moments using (1) only. Apparent Boundary Half-Widths Our primary seismic catalog is the shallow-earthquake subset of the Harvard Centroid Moment Tensor (CMT) cat- To analyze earthquakes by plate setting, it is necessary alog, which was presented in a number of incremental pub- to associate most shallow earthquakes with nearby plate lications (e.g., Dziewonski et al., 1981; Ekstro¨m et al., 2003) boundaries, while classifying the remainder as intraplate and which is presently available in digital form at events.
Load more

Recommended publications
  • I. Convergent Plate Boundaries (Destructive Margins) (Colliding Plates)
    I. Convergent plate boundaries (destructive margins) (colliding plates) 1. Plates collide, an ocean trench forms, lithosphere is subducted into the mantle 2. Types of convergence—three general classes, created by two types of plates —denser oceanic plate subsides into mantle SUBDUCTION --oceanic trench present where this occurs -- Plate descends angle average 45o a. Oceanic-continental convergence 1. Denser oceanic slab sinks into the asthenosphere—continental plate floats 2. Pockets of magma develop and rise—due to water added to lower part of overriding crust—100-150 km depth 3. Continental volcanic arcs form a. e.g., Andes Low angle, strong coupling, strong earthquakes i. Nazca plate ii. Seaward migration of Peru-Chile trench b. e.g., Cascades c. e.g., Sierra Nevada system example of previous subduction b. Oceanic-oceanic convergence 1. Two oceanic slabs converge HDEW animation Motion at Plate Boundaries a. one descends beneath the other b. the older, colder one 2. Often forms volcanoes on the ocean floor 3. Volcanic island arcs forms as volcanoes emerge from the sea 200-300 km from subduction trench TimeLife page 117 Philippine Arc a. e.g., Aleutian islands b. e.g., Mariana islands c. e.g., Tonga islands all three are young volcanic arcs, 20 km thick crust Japan more complex and thicker crust 20-35 km thick c. Continental-continental convergence— all oceaninc crust is destroyed at convergence, and continental crust remains 1. continental crust does not subside—too buoyant 2. two continents collide—become ‘sutured’ together 3. Can produce new mountain ranges such as the Himalayas II. Transform fault boundaries 1.
    [Show full text]
  • Plate Tectonics Says That Earth’S Plates Move Because of Convection Currents in the Mantle
    Bellringer Which ocean is getting smaller and which ocean is getting bigger due to subduction and sea floor spreading? Plate Tectonic Theory Notes How Plates Move • Earth’s crust is broken into many jagged pieces. The surface is like the shell of a hard-boiled egg that has been rolled. The pieces of Earth’s crust are called plates. Plates carry continents, oceans floors, or both. How Plates Move • The theory of plate tectonics says that Earth’s plates move because of convection currents in the mantle. Currents in the mantle carry plates on Earth’s surface, like currents in water carry boats on a river, or Cheerios in milk. How Plates Move • Plates can meet in three different ways. Plates may pull apart, push together, or slide past each other. Wherever plates meet, you usually get volcanoes, mountain ranges, or ocean trenches. Plate Boundaries • A plate boundary is where two plates meet. Faults form along plate boundaries. A fault is a break in Earth’s crust where blocks of rock have slipped past each other. Plate Boundaries • Where two plates move apart, the boundary is called a divergent boundary. • A divergent boundary between two oceanic plates will result in a mid-ocean ridge AND rift valley. (SEE: Sea-Floor Spreading) • A divergent boundary between two continental plates will result in only a rift valley. This is currently happening at the Great Rift Valley in east Africa. Eventually, the Indian Ocean will pour into the lowered valley and a new ocean will form. Plate Boundaries • Where two plates push together, the boundary is called a convergent boundary.
    [Show full text]
  • Santa Monica Mountains National Recreation Area Geologic Resources Inventory Report
    National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science Santa Monica Mountains National Recreation Area Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2016/1297 ON THE COVER: Photograph of Boney Mountain (and the Milky Way). The Santa Monica Mountains are part of the Transverse Ranges. The backbone of the range skirts the northern edges of the Los Angeles Basin and Santa Monica Bay before descending into the Pacific Ocean at Point Mugu. The ridgeline of Boney Mountain is composed on Conejo Volcanics, which erupted as part of a shield volcano about 15 million years ago. National Park Service photograph available at http://www.nps.gov/samo/learn/photosmultimedia/index.htm. THIS PAGE: Photograph of Point Dume. Santa Monica Mountains National Recreation Area comprises a vast and varied California landscape in and around the greater Los Angeles metropolitan area and includes 64 km (40 mi) of ocean shoreline. The mild climate allows visitors to enjoy the park’s scenic, natural, and cultural resources year-round. National Park Service photograph available at https://www.flickr.com/photos/ santamonicamtns/albums. Santa Monica Mountains National Recreation Area Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2016/1297 Katie KellerLynn Colorado State University Research Associate National Park Service Geologic Resources Division Geologic Resources Inventory PO Box 25287 Denver, CO 80225 September 2016 U.S. Department of the Interior National Park Service Natural Resource Stewardship and Science Fort Collins, Colorado The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado, publishes a range of reports that address natural resource topics.
    [Show full text]
  • Active Continental Margin
    Encyclopedia of Marine Geosciences DOI 10.1007/978-94-007-6644-0_102-2 # Springer Science+Business Media Dordrecht 2014 Active Continental Margin Serge Lallemand* Géosciences Montpellier, University of Montpellier, Montpellier, France Synonyms Convergent boundary; Convergent margin; Destructive margin; Ocean-continent subduction; Oceanic subduction zone; Subduction zone Definition An active continental margin refers to the submerged edge of a continent overriding an oceanic lithosphere at a convergent plate boundary by opposition with a passive continental margin which is the remaining scar at the edge of a continent following continental break-up. The term “active” stresses the importance of the tectonic activity (seismicity, volcanism, mountain building) associated with plate convergence along that boundary. Today, people typically refer to a “subduction zone” rather than an “active margin.” Generalities Active continental margins, i.e., when an oceanic plate subducts beneath a continent, represent about two-thirds of the modern convergent margins. Their cumulated length has been estimated to 45,000 km (Lallemand et al., 2005). Most of them are located in the circum-Pacific (Japan, Kurils, Aleutians, and North, Middle, and South America), Southeast Asia (Ryukyus, Philippines, New Guinea), Indian Ocean (Java, Sumatra, Andaman, Makran), Mediterranean region (Aegea, Cala- bria), or Antilles. They are generally “active” over tens (Tonga, Mariana) or hundreds (Japan, South America) of millions of years. This longevity has consequences on their internal structure, especially in terms of continental growth by tectonic accretion of oceanic terranes, or by arc magmatism, but also sometimes in terms of continental consumption by tectonic erosion. Morphology A continental margin generally extends from the coast down to the abyssal plain (see Fig.
    [Show full text]
  • Copyright © by SIAM. Unauthorized Reproduction of This Article Is Prohibited. 82 PHILIPPE GUYENNE and DAVID P
    SIAM J. SCI. COMPUT. c 2007 Society for Industrial and Applied Mathematics Vol. 30, No. 1, pp. 81–101 A HIGH-ORDER SPECTRAL METHOD FOR NONLINEAR WATER WAVES OVER MOVING BOTTOM TOPOGRAPHY∗ † ‡ PHILIPPE GUYENNE AND DAVID P. NICHOLLS Abstract. We present a numerical method for simulations of nonlinear surface water waves over variable bathymetry. It is applicable to either two- or three-dimensional flows, as well as to either static or moving bottom topography. The method is based on the reduction of the problem to a lower-dimensional Hamiltonian system involving boundary quantities alone. A key component of this formulation is the Dirichlet–Neumann operator which, in light of its joint analyticity properties with respect to surface and bottom deformations, is computed using its Taylor series representation. We present new, stabilized forms for the Taylor terms, each of which is efficiently computed by a pseu- dospectral method using the fast Fourier transform. Physically relevant applications are displayed to illustrate the performance of the method; comparisons with analytical solutions and laboratory experiments are provided. Key words. gravity water waves, bathymetry, pseudospectral methods, Dirichlet–Neumann operators, boundary perturbations AMS subject classifications. 76B15, 76B07, 65M70, 35S30 DOI. 10.1137/060666214 1. Introduction. Accurate modeling of surface water wave dynamics over bot- tom topography is of great importance to coastal engineers and has drawn considerable attention in recent years. Here are just a few applications: linear [16, 33] and nonlinear wave shoaling [25, 24, 28, 27], Bragg reflection [35, 15, 36, 14, 30, 33, 4], harmonic wave generation [3, 17, 18], and tsunami generation [37, 22].
    [Show full text]
  • Plate Tectonics Passport
    What is plate tectonics? The Earth is made up of four layers: inner core, outer core, mantle and crust (the outermost layer where we are!). The Earth’s crust is made up of oceanic crust and continental crust. The crust and uppermost part of the mantle are broken up into pieces called plates, which slowly move around on top of the rest of the mantle. The meeting points between the plates are called plate boundaries and there are three main types: Divergent boundaries (constructive) are where plates are moving away from each other. New crust is created between the two plates. Convergent boundaries (destructive) are where plates are moving towards each other. Old crust is either dragged down into the mantle at a subduction zone or pushed upwards to form mountain ranges. Transform boundaries (conservative) are where are plates are moving past each other. Can you find an example of each type of tectonic plate boundary on the map? Divergent boundary: Convergent boundary: Transform boundary: What do you notice about the location of most of the Earth’s volcanoes? P.1 Iceland Iceland lies on the Mid Atlantic Ridge, a divergent plate boundary where the North American Plate and the Eurasian Plate are moving away from each other. As the plates pull apart, molten rock or magma rises up and erupts as lava creating new ocean crust. Volcanic activity formed the island about 16 million years ago and volcanoes continue to form, erupt and shape Iceland’s landscape today. The island is covered with more than 100 volcanoes - some are extinct, but about 30 are currently active.
    [Show full text]
  • Presentation on Pacific Plate and Associated Boundaries
    PACIFIC PLATE AND ASSOCIATED BOUNDARIES The Pacific Plate • Pacific Plate is the largest plate and an oceanic plate. • It shares its boundaries with numerous plates namely; North American Plate.(Convergent and transform fault) Philippine Plate.(Convergent) Juan de Fuca Plate.(Convergent) Indo – Australian Plate.(Convergent, Transform Fault) Cocos Plate.(Divergent) Nazca Plate.(Divergent) Antarctic Plate.(Divergent,Transform Fault) Types of Plate Boundaries • Convergent Boundary: Subduction zones where two plates converges. Eg; Aleutian Islands(Alaska) • Divergent Boundary: Spreading centres where two plates move away from each other. Eg; East Pacific Rise (MOR, Pacific Ocean). • Transform Faults: Boundary where two plates slide past each other. For Eg. ; San Andreas Fault. BOUNDARY WITH ANTARCTIC PLATE DIVERGENT BOUNDARY • Pacific – Antarctic Ridge TRANSFORM FAULT • Louisville Seamount Chain Pacific – Antarctic Ridge Pacific – Antarctic Ridge(PAR) is located on the seafloor of the South Pacific Ocean. It is driven by the interaction of a mid oceanic ridge and deep mantle plumes located in the eastern portion of East Pacific Ridge. Louisville Seamount Chain It is the longest line of seamount chain in the Pacific Ocean of about 4,300 km, formed along the transform boundary in the western side between Pacific plate and Antarctic plate. It was formed from the Pacific Plate sliding over a long – lived centre of upwelling magma called the Louisville hotspot. BOUNDARY WITH PHILIPPINE PLATE CONVERGENT BOUNDARY • Izu – Ogasawara Trench • Mariana Trench Izu – Ogasawara Trench It is an oceanic trench in the western Pacific Ocean. It stretches from Japan to northern most section of Mariana Trench. Here, the Pacific Plate is being subducted beneath the Philippine Sea Plate.
    [Show full text]
  • What's the Difference?
    New Zealand American Submarine Ring of Fire 2007 What’s The Difference? FOCUS SEATING ARRANGEMENT Volcanic processes at convergent and divergent Classroom style if students are working individu- tectonic plate boundaries ally, or groups of two to four students GRADE LEVEL MAXIMUM NUMBER OF STUDENTS 9-12 (Earth Science) 30 FOCUS QUESTION KEY WORDS How do volcanic processes differ at convergent Volcano and divergent tectonic plate boundaries? Caldera Hot spot LEARNING OBJECTIVES Ring of Fire Students will be able to compare and contrast Asthenosphere volcanoes at convergent and divergent plate Lithosphere boundaries. Magma Fault Students will be able to identify three geologic Transform boundary features that are associated with most volcanoes Convergent boundary on Earth. Divergent boundary Subduction Students will be able to explain why some volca- Tectonic plate noes erupt explosively while others do not. BACKGROUND INFORMATION MATERIALS The Submarine Ring of Fire is an arc of active vol- Copies of “Submarine Volcanism Worksheet,” canoes that partially encircles the Pacific Ocean one copy for each student or student group Basin, including the Kermadec and Mariana Islands in the western Pacific, the Aleutian Islands AUDIO/VISUAL MATERIALS between the Pacific and Bering Sea, the Cascade (Optional) Computer projection equipment to Mountains in western North America, and numer- show downloaded video materials ous volcanoes on the western coasts of Central America and South America. These volcanoes TEACHING TIME result from the motion of
    [Show full text]
  • Assessment of Peak Tsunami Amplitude Associated with a Great
    Assessment of peak tsunami amplitude associated with a great earthquake occurring along the southernmost Ryukyu subduction zone for Taiwan region Yu-Sheng Sun1, Po-Fei Chen1, Chien-Chih Chen1, Ya-Ting Lee1, Kuo-Fong Ma1 and Tso-Ren Wu2 5 1Department of Earth Sciences, National Central University, Taoyuan City, Taiwan 320, R.O.C. 2Graduate Institute of Hydrological and Oceanic Sciences, National Central University, Taoyuan City, Taiwan 320, R.O.C. Correspondence to: Yu-Sheng Sun ([email protected]) Abstract. The southernmost portion of the Ryukyu Trench closed to Taiwan island is a potential region to generate 7.5 to 8.7 tsunami earthquakes by shallow rupture. The fault model for this potential region dips 10º northward with rupture length of 10 120 km and width of 70 km. The earthquake magnitude estimated by fault geometry is Mw 8.15 with 8.25 m average slip as a constrain of earthquake scenario. The heterogeneous slip distributions over rupture surface are generated by stochastic slip model, the slip spectrum with k-2 decay in wave number domain, and they are consistent with above identical seismic conditions. The results from tsunami simulation illustrate that the propagation of tsunami waves and the peak wave heights largely vary in response to the slip distribution. The wave phase changing is possible as the waves propagate, even under the same seismic 15 conditions. The tsunami energy path is not only following the bathymetry but also depending on slip distribution. The probabilistic distributions of peak tsunami amplitude calculated by 100 different slip patterns from 30 recording stations reveal the uncertainty decreases with distance from tsunami source.
    [Show full text]
  • Earth Science
    EARTH SCIENCE A Review of our Earth HISTORY OF THE EARTH The Geologic Time Scale HOW OLD IS THE EARTH? Geologists use fossil records to separate the history of the Earth The divisions are from largest to smallest length of time eon era period epoch 4.6 BILLION YEARS OLD Eon: measured in billions of years Era: measured in hundreds of millions of years and marked by differences in life-forms that are preserved in rocks. Period: measured in tens of millions of years and marked by life-forms that were abundant and then extinct Epoch: measured in millions of years and marked by different groups of organisms THE FOUR EONS Hadean (4.6-3.9 bya) Archeozoic (3.9-2.5 bya) Precambrian Proterozoic (2.5-0.54 bya) Time Phanerozoic (540 mya - present) WHAT ERA DO WE COME IN? Precambrian times: bacteria Paleozoic Era (540-248 mya): fish, reptiles, marine invertebrates, land plants and amphibians Mesozoic Era (248-65 mya): age of dinosaurs (triassic, jurassic & cretaceous) Cenozoic Era (65 mya - present): age of mammels WHAT PERIOD DO I HAVE HUMAN? Cenozoic Era Tertiary Period Paleocene Eopch Eocene Epoch Oligocene Epoch Miocene Epoch Pliocene Epoch Quaternary Period Pleistocene Epoch You are Holocene Epoch here RELATIVE AGE OF ROCKS The relative age of rocks can be determined by examining the different horizontal layers rocks fossils unconformities ABSOLUTE AGE DATING Radiometric Dating Half-life Thorium-232 (14.0 billion yrs) to Lead-208 Uranium-238 (4.5 billion yrs) to Lead-206 Uranium-235 (0.7 billion yrs) to Lead-207 Carbon-14 (only 5,730 yrs) to Nitrogen-14 GEOLOGIC TIMELINE ASSIGNMENT http://www.learner.org/vod/vod_window.html? pid=321 Complete the “Geologic Timeline” found on the “APES Assignment” page.
    [Show full text]
  • Plate Tectonics and Regional Features the SURFACE of EARTH IS NOTABLE for Its Dramatic Mountains, Beautiful Valleys, and Intricate Coastlines
    Final PDF to printer CHAPTER 10 Plate Tectonics and Regional Features THE SURFACE OF EARTH IS NOTABLE for its dramatic mountains, beautiful valleys, and intricate coastlines. Beneath the sea are unexpected features, such as undersea mountain ranges, deep ocean trenches, and thousands of submarine mountains. In this chapter, we examine the distribution of these features, along with the locations of earth- quakes and volcanoes, to explore the theory of plate tectonics. These images of the world show large topographic features on the land, colored using satellite data that show areas of vegetation in green and areas of rocks and sand in tan. Colors on the seafloor indicate depths below sea level, ranging from light blue for seafloor that is at relatively shallow depths to dark blue for seafloor that is deep. 10.00.a1 The seafloor west of North America displays a long, fairly straight fracture, named the Mendocino Fracture Zone, that trends east-west and ends abruptly at the coastline. North of this fracture, a ridge called the Juan de Fuca Ridge zigzags across the seafloor. What are these features on the seafloor and how did they form? South America has two very different sides. The mountainous Andes parallel the western coast, but a wide expanse of lowlands, including the Amazon Basin, makes up much of the rest of the continent. The western edge of the continent drops steeply into the Pacific Ocean and is flanked by a deep trench. The eastern edge of the continent continues well beyond the shoreline and forms a broad bench covered by shallow waters (shown in light blue).
    [Show full text]
  • Information Circular 85. Washington State Earthquake Hazards
    WASHING1rON STATE EARTHQUAKE:HAZARDS by LINDA LAWRANCE NOS , ANTHONY QAMAR, AND GERALD W. THORSEN WASHING TON DIVISION OF GEOLOGY AND EARTH RESOURCE INFORMATION CIRCULAR 85 1988 WASHINGTON STATE DEPARTMENT OF Natural Resources Brian Boyle - Commissioner of Public Lands Art Stearns - Supervisor Division of Geology and Earth Resources Raymond Lasmanis, State Geologist Cover photo: Damage to an unreinforced masonry building in downtown Centralia in 1949. A man was killed by the falling upper walls of this two-story corner building. Unreinforced masonry walls, gables, cornices, and partitions were the most seriously damaged structures in the 1949 and 1965 earthquakes. Inferior mortar and inadequate ties between walls and floors compounded the damage. (Photo from the A. E. Miller Col­ lection, University of Washington Archives) -- WASHING TON ST ATE EARTHQUAKE HAZARDS by LINDA LAWRANCE NOSON, ANTHONY QAMAR, AND GERALD W. THORSEN WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES INFORMATION CIRCULAR 85 1988 • . ' NaturalWASHING10N STATE Resources DEPARTMENT OF Brtan Boyle • Commasloner 01 P\lbllc Lands Art Steorns • Supervisor Divisfon 0 1 Geology and Earth Resources Raymond Lasmanis. State Geo!ogisl The authors gratefully acknowledge review of the manuscript of this publication by members of the Geophysics Program. University of Washington. This report is available from: Publications Washington Department of N arural Resources Division of Geology and Earth Resources Mail Stop PY-12 Olympia, WA 98504 The printing of this report was supported by U.S. Geological Survey Earthquake Hazards Reduction Program Agreement No. 14-08-0001-A0509. This publication is free, but please add $1.00 to each order for postage and handling. Make checks or money orders payable to the Department of Natural Resources.
    [Show full text]