Chapter 4: Problem 7

Describe the process of subduction at a consuming boundary. (E)

Short Answer

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At a consuming boundary, the denser oceanic plate subducts beneath the less dense continental plate due to gravitational forces and mantle convection currents. This results in the formation of an oceanic trench, which marks the beginning of the subduction process. As the oceanic plate sinks deeper, it partially melts, producing magma that rises to form volcanic arcs on or near the continental plate. The movement and interaction of the plates can also produce earthquakes and lead to the formation of mountain ranges.

Step by step solution

Introduction to Subduction

Subduction is a geological process that occurs at convergent plate boundaries where one tectonic plate moves under another and sinks into the mantle due to forces exerted on it. Consuming boundaries are also known as destructive plate boundaries because they involve the destruction of Earth's lithosphere. Here, we will focus on explaining the process of subduction at a consuming boundary.

Identify the types of tectonic plates involved

At a consuming boundary, two different types of tectonic plates typically interact: an oceanic plate and a continental plate. Oceanic plates consist of denser basaltic rocks, while continental plates are composed of less dense granitic rocks. It is important to identify which type of plate is subducting and which one is overriding, as this will determine the features associated with subduction at the consuming boundary.

Understand plate movement and forces at the boundary

At a consuming boundary, the denser oceanic plate moves beneath the less dense continental plate, sinking into the mantle. The force of gravity plays a significant role in subduction, as the denser oceanic plate is pulled downward into the mantle. Additionally, the movement of the plates is driven by the convection currents in the mantle, which causes the oceanic plate to be pushed below the continental plate.

Formation of an oceanic trench

As the oceanic plate subducts beneath the continental plate, the shape of the boundary between the two plates causes the formation of a deep linear depression called an oceanic trench. These trenches are the deepest parts of the Earth's oceans and mark the position where the oceanic plate begins to subduct.

Partial melting of the oceanic plate

As the oceanic plate sinks deeper into the mantle, it is subjected to increasing temperatures and pressures. This causes the basaltic rocks of the oceanic plate to partially melt, forming a layer of molten rock called magma.

Magma rises and forms volcanic arcs

The newly-formed magma, being less dense than the surrounding material, begins to rise toward the Earth's surface. As the magma rises, it may collect in magma chambers beneath the continental plate or break through the surface to form volcanic arcs on or near the continental plate.

Earthquakes and the formation of mountain ranges

The movement of the oceanic plate beneath the continental plate can cause intense stress along the boundary, resulting in earthquakes. Additionally, the pressure exerted by the subducting oceanic plate can cause the continental plate to crumple, leading to the formation of mountain ranges near the consuming boundary. In conclusion, the process of subduction at a consuming boundary involves the interaction of tectonic plates, resulting in various geological features such as oceanic trenches, volcanic arcs, earthquakes, and mountain ranges due to the sinking of the denser oceanic plate beneath the less dense continental plate.

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Describe the process of subduction at a consuming boundary. (E)

Short Answer

Step by step solution

Introduction to Subduction

Identify the types of tectonic plates involved

Understand plate movement and forces at the boundary

Formation of an oceanic trench

Partial melting of the oceanic plate

Magma rises and forms volcanic arcs

Earthquakes and the formation of mountain ranges

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