2010FEATS1010ASSIGN4

2010FEATS1010ASSIGN4 - Lab. Session:_ Name:_ Student #_...

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Name:_________________________________ Lab. Session: _______ Student #________________________________ YORK UNIVERSITY Fall 2010 EATS 1010 3.0 Laboratory Exercise #4 PLATE TECTONICS This lab is divided into three parts, each dealing with a different aspect of plate tectonics. Read the lab over beforehand and bring a pencil, metric ruler and either your textbook or your class notes to the laboratory . Allow yourself about one hour of time for each exercise. Instructions are given for each part. Follow the procedures as outlined and fill in your answers to all the questions on the work sheets provided. Hand in your completed lab before the end of the session. Be sure your name is on the front page and also on each of your answer sheets (in case some of the pages come apart). PART 1. ISLAND ARC/OCEAN TRENCH EARTHQUAKES Introduction In the western and northern Pacific Ocean there are many arc-shaped groups of islands. The Aleutians, the Marianas, Japan and Indonesia are all examples. There are also island arcs in the Caribbean and South Atlantic. Island arcs have two important characteristics: (1) they all have deep ocean trenches nearby and (2) they are areas of volcanism and intense earthquake activity. The location in the Earth where an earthquake occurs is called its focus. Geophysicists have discovered that most of the world's intermediate and deep-focus earthquakes (below 100 km) occur near island arc/trench systems. For many years there was great curiosity about the unusual character of island arcs. There was no explanation for them prior to the Theory of Plate Tectonics. It proposed that if oceanic plates are created at a mid-ocean ridge, there must be some place where the far ends of the plates dive back down into the mantle. This occurs in the vicinity of island arcs producing the trench as well as volcanic and earthquake activity. Earthquake studies in such regions provide evidence of subduction of the diving plate.
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Objective In this exercise you will: 1) plot and interpret an earthquake focus profile, and 2) explain the seismic characteristics of a subduction zone. Procedure 1. The table below lists the locations of earthquakes that have occurred in the Marianas Trench area. Plot the location of each on the Earthquake Focus Profile provided as page 4. 2. Study your earthquake focus profile and answer the questions on page 3 in the spaces provided. Earthquakes of the Marianas Trench Area Horizontal Horizontal Horizontal Depth (km) Distance from Depth (km) Distance from Depth (km) D i s t a n c e from Trench (km) Trench (km) Trench (km) 0 16 0 50 0 72 0 96 32 168 66 132 83 168 83 184 116 232 116 248 150 200 150 260 200 216 200 248 216 264 232 254 250 264 300 360 350 364 350 400 383 408 416 432 448 448 472 416 472 432 500 450 500 458 516 432 516 456 550 500 580 450 580 464 600 480 600 508 600 524 624 508 624 524 650 532 667 548
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Page 3 Questions 2.What is the relation between the depth of earthquakes and their distance from the Tonga
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2010FEATS1010ASSIGN4 - Lab. Session:_ Name:_ Student #_...

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