Prelab Exercise Name:______________________________________
Laboratory 2: Plate Tectonics
Please read the background information between pages 30 and 42 in your lab manual, then answer the following questions:
Please briefly describe the relative motion of Earth's lithospheric plates at convergent, divergent, and transform boundaries. In other words, how do two plates move relative to one another at each type of plate boundary?
What geologic evidence indicates that the now widely spaced continents were once joined together?
Earth's outer, brittle shell, called the lithosphere, consists of the entire crust plus the uppermost portion of the underlying mantle, down to a depth of approximately ____________ kilometers (see Fig 2.1 for correct answer).
Beneath the brittle lithosphere, a soft, weak, plastic layer occurs, called the _______________________ (see Fig 2.1).
According to plate tectonic theory, most earthquakes, volcanism, and mountain building occur at plate ______________________.
Earth's ____________ is nearly 3,000 kilometers thick and occurs in between the crust and molten outer core.
In Figure 2.7, find the thick black line labeled "Peridotite Solidus." This line, based on laboratory experiments, provides a graph of the temperature at which the typical mantle rock, peridotite, begins to melt in relation to depth and depth. Think of this line as a graph of peridotite melting temperature vs. depth/pressure.
Peridotite rock will remain solid if pressure and temperature conditions are such that it plots to the left of the peridotie solidus in Figure 2.7; however, if pressure and temperature conditions are such that peridotite plots to the right of the peridotite solidus, it will begin to melt.
If a mass of peridotite were subjected to temperature and pressure conditions depicted by point X in Figure 2.7, the peridotite would remain solid / begin to melt (circle correct answer).
If a mass of peridotite were subjected to a temperature of 1500 degrees celcius and a pressure of 10,000 atmospheres, it would remain solid / begin to melt (circle correct answer).
Mid-plate volcanism like that occurring on the Big Island of Hawaii is difficult to explain by plate tectonic processes alone. According to the mantle plume or hotspot hypothesis, mantle plumes are stationary, vertical columns of hot rock that originate beneath the lithospheric plates. As a plate moves over a stationary mantle plume, a volcano sometimes develops directly above the plume. As the plate continues to move, the volcano moves off of the plume and eventually becomes inactive. Eventually, a new volcano may form atop the plume once more.
Locate the Island of Hawaii (the Big Island) in the southeastern portion of the Figure 2.10, bottom map. The Island of Hawaii consists of three volcanoes, Mauna Kea, Kilauea, and Mauna Loa.
Assume that a stationary mantle plume occurs beneath the island of Hawaii. Based on the age progression of the Hawaiian Islands shown in Figure 2.10, the Pacific plate moving over the Hawaiian mantle plume is migrating toward the northeast / northwest / southeast / southwest (circle correct answer).