Tectonic Earth

4.4 Life on the Edge

In this section of the assignment, you will analyze population density, tectonic plate boundaries, volcanoes, and earthquake activity, identifying areas of subduction along tectonic plate boundaries in South and Southeast Asia. By the end of this section, you will be able to:

  • Describe the relationship between zones of high seismic or volcanic activity and tectonic plate boundaries.
  • Identify densely populated areas that are most at risk for volcanic and/or seismic disasters.

Where are the most densely populated areas in Asia?

Step 1: Go to the ArcGIS Online map, Life on the Edge, and explore it.

Step 2: With the Details button depressed, click the button, Show Contents.

Geographic Question
  • Where the darkest colors indicate high population density and the cream colors indicate low population density, describe the population density pattern in East Asia.

Step 3: Click the button Bookmarks. Choose Mumbai, India.

Step 4: Click the green dot on the map to view its population. (Zoom out, if necessary.)

Geographic Question
  • What is Mumbai’s population?
  • Using the Kunming, China, and Tokyo, Japan, bookmarks, what are the populations of both these cities?

Where did high-magnitude earthquakes occur?

Step 5: In the upper-left corner of the map, click the Default Extent (house) button.

Step 6: Turn on the Earthquake Magnitude 5.7+ (2004-2007) layer.

Geographic Questions
  • In general, where did earthquakes with a magnitude greater than 5.7 occur?
  • Which densely populated areas did these earthquakes occur?

Are cities in East Asia near active volcanoes?

Step 7: Turn off the layer, Earthquakes 5.7+ (2004-2007).

Step 8: turn on the layer, Volcanoes By Type.

Step 9: Pause your pointer over the Volcanoes By Type layer name and click the Show Legend icon. Volcanoes are grouped into active, potentially active, and solfatara states (venting mostly hot gas).

Step 10: Note the different symbols used for each type of volcano.

Step 11: Find a city near a volcano and measure, in kilometers, between the nearest active volcano and that city. Click Measure, select the Distance button, and from the drop-down list, choose a unit of measurement. Click once to start the measurement on the map, click again to change direction, and double-click to stop measuring. Hint: Position the area of interest on the map so that the Measure window does not obscure it.

Where might tectonic plate subduction occur?

Step 12: Turn off all layers, except the layer, Earth’s Tectonic Plates.

Step 13: Click the plates to discover their names.

Many of the tectonic plate boundaries around the Pacific Ring have areas called subduction zones, where one plate is diving underneath another one and can be identified by deep underwater trenches and volcanic island arcs along tectonic plate boundaries.

Step 14: Turn on the layer, World Imagery.

Geographic Question
  • By turning the Plate Boundaries layer off and on as needed, it appears that subduction is occurring along the western boundary of the Pacific tectonic plate and the eastern and southern boundaries of the Indo-China tectonic plate.

Where are future cities at risk?

Step 15: Turn on the two layers, Major Cities and Volcanoes by Type.

Step 16: Zoom and pan the map, clicking cities to find the closest to active volcanoes and subduction zones

Geographic Question
  • List three cities that may be at risk of volcanic or seismic events in the future?

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