Review for Exam #3
(November 12, 2009)
For the exam, you should be able to do the following:
w List the geotectonic settings in which volcanoes occur (subduction zones, divergent zones, hotspots).
w Tell why volcanoes occur at each of these settings.
w Tell what makes rock melt in the crust and mantle settings where volcanoes occur. Describe the process in terms of changing temperature, changing pressure, and introduction of "impurities" (water and sediments) into the melt.
w Draw a graph illustrating the varying conditions that lead to rock melting.
w Explain what a hotspot is, and tell how it fits into a geotectonic framework. Give an example.
w Describe the differences between lava of mafic and felsic composition, and tell how these differences lead to variation in these aspects:
form/shape/profile of the volcano
q type of material erupted, and
q the volcano's "eruptive style".
w Define the terms pahoehoe and aa, and tell where these materials might be found.
w After viewing the Raging Planet film "Volcano", describe some of the strategies people use to cope with life next to a volcano.
LATITUDE AND LONGITUDE
w Describe the longitude and latitude coordinate system for locating points on Earth's surface.
w Find the approximate (degrees) latitude and longitude of a general area using a world map.
w Explain how the measurement units of degrees, minutes, and seconds are used to indicate latitude and longitude.
w Find precise latitude and longitude coordinates of a specific site using a topographic quadrangle map.
w Explain what is meant by "7.5 minute series" in reference to a topographic quadrangle map.
w Log in to the class wiki and add your name to the "Earthquake Maps" list. Find the latitude and longitude coordinates of the study area for which you sign up.
w Be informed enough about use the USGS earthquake information site to complete the homework assignment on Earthquake Maps.
w Explain the difference between the focus of an earthquake, and the epicenter.
w Tell what the term magnitude means as applied to earthquakes.
w Explain how a seismometer works.
w Explain why every seismograph includes at least three seismometers.
w Describe P-waves and S-waves and explain the differences between them.
w Demonstrate how to use a seismic P-S lag (time difference) to determine the distance to an earthquake epicenter.
w Show how to locate the epicenter of an earthquake using seismograms from three different stations. Explain why it is necessary to use data from at least three stations.
w After viewing some of the videos and animations of the Indian Ocean tsunami of December 26, 2004, research seismograms from the event.
w Use seismograms to find the epicenter of an earthquake using the Indian Ocean tsunami as an example. (Extra copies of the map, the seismograms , and the P-S lag (time difference) graph are linked to this page. This exercise is abridged from an exercise copyrighted in 2004 by Dave Robison and Steve Kluge.)
EARTHQUAKES AND GEOTECTONICS
w Using the earthquake maps the class produced, arrange them in meaningful groups based on the patterns of earthquake epicenters and based on the patterns of focal depths you observe in each. The worksheet appears at this link.