GroupAssig3
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Moorpark College *
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Geology
Date
Feb 20, 2024
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4
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1 Group Assignment #3: Earth’s Active Surface Introduction The extremely high temperatures of Earth’s core causes material in the surrounding mantle to become hot, expand, and rise toward the surface. The mantle material then cools and sinks, resulting in a circular motion of material moving beneath Earth’s surface. This circulation of mantle mantel material causes the continental and oceanic plates to move across Earth’s surface. At various locations on Earth’s
surface, we are able to observed plates colliding, plates separating, and plates moving horizontally with respect to each other. Objectives The purpose of this exercise is to 1)
Explain the theory of plate tectonics 2)
Describe the difference between rift and subduction zones 3)
Describe the relationship between fault zones and mountain building Figure 1. Oceanic to Continental Plate convergence zone. This image shows a cross section of Earth’s surface and its underlying mantle. At this particular location of the surface (D), the dense oceanic plate is forced beneath the less dense continental crust. The dense oceanic plate experiences higher temperatures and pressures. This interaction between the oceanic plate and continental plate causes molten material to move upward through the continental plate until it breaks the surface in the form of volcanoes.
2 Plate Tectonics Geology
is the study of Earth’s crust and the processes that have shaped its surface throughout history. Plate tectonics
is a theory that explains how slow motions within the mantle of Earth move large segments of the crust, resulting in a gradual “drifting” of the continents as well as the formation of mountains and other large-scale geological features. Earth’s crust and upper mantle (to a depth of about 60 kilometers) are divided into about a dozen tectonic plates that fit together like the pieces of a jigsaw puzzle: As the plates slowly move, they bump into each other, causing dramatic changes in Earth
’s crust over time. Four kinds of interactions between crustal plates at their boundaries are: (1) they can pull apart, (3) they can slide alongside each other, or (2) one plate can burrow under another, (4) they can jam together. Plates pull apart from each other along rift zones
, such as the Mid-Atlantic ridge, driven by upwelling currents in the mantle. As new crust is added to Earth, the old crust must go somewhere. When two plates come together, one plate is often forced beneath another in what is called a subduction zone
. Along much of their length, the crustal plates slide parallel to each other. These plate boundaries are marked by cracks or faults
. Volcanoes
mark locations where lava rises to the surface. One example is mid ocean ridges, which are long undersea mountain ranges formed by lava rising from Earth’s mantle at plate boundaries. A second major kind of volcanic activity is associated with subduction zones, and volcanoes can also appear in regions where continental plates are colliding. Other volcanic activity occurs above mantle “
hot spots
”—
areas far from plate boundaries where heat is nevertheless rising from the interior of Earth. One of the best-known hot spots is under the island of Hawaii, suppling heat to two volcanoes on land, one under the ocean.
Figure 2. Earth’s Continental Plates
. This map shows the major plates into which the crust of Earth is divided. Arrows indicate the motion of the plates at average speeds of 4 to 5 centimeters per year (similar to how fast your hair grows).
3 Group Assignment #3: Earth’s Active Surface
Name ____________________________________ Group Partner(s) ____________________________________ Date/Time ____________________________________ Use figures 1 and 2 above to answer the following questions. 1.
Which way is the oceanic plate 1 moving? Circle one and explain your reasoning. Left Right Up Down ___________________________________________________________________________ 2.
Which way is the oceanic plate 2 moving? Circle one and explain your reasoning. Left Right Up Down ___________________________________________________________________________ 3.
Which is hotter, the piece of mantle material at Position A, or the piece of mantle material at Position B? Explain your reasoning. ___________________________________________________________________________ 4.
What direction is the piece of mantle material moving at Position B? Circle one and explain your reasoning. Left Right Up Down _____________________________________________________________________________________________________
5.
What direction is the piece of mantle material moving at Position C? Circle one and explain your reasoning. Left Right Up Down _____________________________________________________________________________________________________
6.
Just above Point C on Figure 1 is a tropical island. What will eventually happen to the island as the oceanic plate moves? Why? Circle one and explain. Left Right Up Down _____________________________________________________________________________________________________
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4 7.
Consider Point D on Figure 1, what kind of interaction between crustal plates at their boundaries is happening? Explain your reasoning. ___________________________________________________________________________ 8.
Imagine that an impact occurred on the continental plate millions and millions of years ago, leaving behind an impact crater near the right side of the base of the volcano (above Point F). Why would there be little evidence of this impact crater found today? _____________________________________________________________________________________________________ ___________________________________________________________________________ 9.
The volcano above Point C is in the middle of an oceanic plate, and obtains its energy from what type of mantle activity? ______________________________ 10.
Consider the image below (Figure 3) of the rocky and crater-covered Moon. Its very old surface has remained virtually unchanged over the las few billion years. Do you think the Moon has an active, hot, and molten interior? Circle one and explain your reasoning. Yes No
___________________________________________________________________________ ___________________________________________________________________________ Figure 3. Heavily cratered Lunar surface.