Try This: The Effects of Plate Movements

Question

The Cascade Range is a line of volcanic mountains near the west coast of North America. The mountain range formed near a plate boundary. You will draw a cross-section diagram that shows what occurs at the boundary between the two plates. Your diagram should show what happens under Earth’s surface, and how that causes the formation of the line of volcanoes. You can refresh your memory by reviewing lessons in the unit.

Answer 1

To create a cross-section diagram showing the effects of plate movements at the boundary between the oceanic and continental plates that contribute to the formation of the Cascade Range, follow these steps:

Diagram Components:

1. Earth's Layers:

   • Draw the crust, mantle, outer core, and inner core. Label each layer.

2. Plates:

   • Represent the oceanic plate (the Juan de Fuca Plate) and the continental plate (the North American Plate). Indicate their boundaries.

3. Subduction Zone:

   • Illustrate the oceanic plate sliding beneath the continental plate at a convergent boundary. Show the oceanic plate being forced down into the mantle in a downward slant.

4. Mantle and Magma Formation:

   • Indicate areas of melting where the subducted oceanic plate heats up and causes partial melting of the mantle. Draw these melted rock materials as magma pools forming beneath the continental plate.

5. Volcanic Activity:

   • Show magma rising from the mantle and accumulating in magma chambers beneath the surface of the continental plate. Include arrows indicating this upward movement.
   • Illustrate the formation of volcanic structures as the magma pushes through the continental crust. Label these as "volcanoes."

6. Eruption and Surface Features:

   • Indicate the potential for eruptive events by showing ash clouds or lava flows emerging from the volcanoes on the surface.
   • Label the Cascade Range at the surface where the volcanoes are located.

Diagram Example:

--------------------------------------------------
|                  Surface (Cascade Range)       |
|    ^   ^           ^   ^          ^   ^       | 
|  Volcano Volcano  Volcano Volcano  Volcano      |
|                  (Eruptions)                   |
--------------------------------------------------
|                                                |
|                  Continental Crust             |
|                                                |
|                 (North American Plate)        |
--------------------------------------------------
|                      \   /                     |
|                       \ /                      |
|             ↓         |         ↑              |
|          Subducting Oceanic Plate              |
|             (Juan de Fuca Plate)               |
--------------------------------------------------
|          Melting Mantle & Magma Formation      |
|                     (Magma Pool)               |
--------------------------------------------------
|                                                |
|                      Mantle                    |
|                                                |
--------------------------------------------------

Key Explanations:

• Subduction: The process where the denser oceanic plate is forced under the less dense continental plate.
• Magma Formation: As the oceanic plate descends, it heats up and releases water, lowering the melting point of the surrounding rock and generating magma.
• Volcanic Eruptions: The magma that rises to the surface contributes to the formation of the Cascade Range through eruptions.

This diagram will help visualize the geological processes involved in the formation of the Cascade Range due to the movements of tectonic plates.