GEOL 1210 title

Characterizing Plate Boundaries

This activity is intended to help you learn about the geologic characteristics of the different types of plate boundaries you've been reading about in Chapter 1. Before you begin, be sure that you have read through the section on the natures of the different types of plate boundaries in Chapter 1 your text and thought about the question, "In light of the different processes that occur along divergent, convergent and shear boundaries how would I expect patterns of volcanism, seismicity (earthquake activity) and so on to differ along each type of boundary?" For example, pulling apart thin lithosphere might be expected to produce shallow earthquakes along a divergent boundary, but what about the sinking of thick ocean lithosphere along a subduction zone—a type of convergent boundary? Or, based on density and the principle of isostasy, how would you expect the elevation of an oceanic plate to differ between where it's warm (because of rising asthenosphere beneath it) and where it's cold (because of a long history of cooling at the surface)?

Once you feel that you have a sense of how different types of plate boundaries are likely to differ in terms of their basic geologic characteristics, follow the steps below:

Earthquakes

Compare the maps showing the locations of the plate boundaries (purple lines) and earthquake epicenters (colored dots) for each of the three sites. Note that the colors assigned to the earthquakes indicate their depths, not magnitudes: red = 0-33 km; yellow = 33-70 km; green = 70-300 km and blue = 300-700 km. For each site answer the following questions:

Site 1 Site 2 Site 3
Boundary 1 Boundary 2 Boundary 3
Boundary 1 Boundary 2 Boundary 3

Volcanoes

Compare the maps showing the locations of the plate boundaries (purple lines) and locations of young volcanoes (red dots) for each of the three sites. Most of the boundary at site 2 is underwater, so we rarely witness volcanic eruptions along it. Therefore, assume that the distribution of volcanoes in Iceland is typical of that elsewhere along this boundary. For each site answer the following questions:

Site 1 Site 2 Site 3
Boundary 1 Boundary 2 Boundary 3
Boundary 1 Boundary 2 Boundary 3

Seafloor Age

Compare the maps showing the locations of the plate boundaries (purple lines) and the ages of the adjacent seafloor crust (colored bands) for each of the three sites. Note that "warmer" colors indicate younger crust and "cooler" colors indicate older crust according to the following scheme: red = 0 to 9.7 Ma (millions of years old); shades of orange = 9.7 to 47.9 Ma; shades of yellow = 47.9 to 67.7 Ma; shades of green = 67.7 to 131.9 Ma; and shades of blue = 131.9 to 180 Ma. Dark gray indicates seafloor for which no age data is available and light gray indicates continents. For each site answer the following questions:

Site 1 Site 2 Site 3
Boundary 1 Boundary 2 Boundary 3
Boundary 1 Boundary 2 Boundary 3

Surface elevation

Compare the maps showing the locations of the plate boundaries (purple lines) and the elevation of Earth's surface (colored patterns) for each of the three sites. Note that on the elevation maps "warmer" colors generally indicate higher elevations and "cooler" colors indicate lower ones according to the following scheme: above sea level the highest elevations are shown in purple, moderate elevations in brown and the lowest elevations in green; below sea level the shallowest depths are shown in turquoise, moderate depths in bluish-purple and the greatest depths in pink. Surface elevation is complex near Iceland, so focus on the part of the boundary south of the island. For each site answer the following questions:

Site 1 Site 2 Site 3
Boundary 1 Boundary 2 Boundary 3
Boundary 1 Boundary 2 Boundary 3