Question

Match each of these volcanic regions with one of the three zones of volcanism (convergent plate boundaries, divergent plate boundaries, or intraplate volcanism): a. Crater Lake b. Hawaii's Kilauea c. Mount St. Helens d. East African Rift e. Yellowstone f. Vesuvius g. Deccan Plateau h. Mount Etna

Short answer

Crater Lake (Convergent), Kilauea (Intraplate), Mount St. Helens (Convergent), East African Rift (Divergent), Yellowstone (Intraplate), Vesuvius (Convergent), Deccan Plateau (Intraplate), Mount Etna (Convergent).

Step-by-step solution

Identifying Crater Lake's Volcanism

Crater Lake is located in Oregon, USA, and is the result of a volcanic eruption that destroyed the volcano's peak, leading to the formation of a caldera which eventually filled with water. This type of activity is typically associated with **convergent plate boundaries**, where oceanic crust is subducted beneath continental crust.

Identifying Hawaii's Kilauea Volcanism

Hawaii's Kilauea is a shield volcano located in the middle of the Pacific Plate. It is not situated at a plate boundary but rather over a hotspot, making it an example of **intraplate volcanism**.

Identifying Mount St. Helens' Volcanism

Mount St. Helens is located in Washington, USA, and is a part of the Cascade Range, which is known for its volcanic activity due to the subduction of the Juan de Fuca plate beneath the North American plate. This places it in a **convergent plate boundary** zone.

Identifying the East African Rift's Volcanism

The East African Rift is an area where the African Plate is being pulled apart, leading to volcanic activity. This type of tectonic activity is associated with **divergent plate boundaries**.

Identifying Yellowstone's Volcanism

Yellowstone is located in Wyoming, USA, and is known for its volcanic activity related to the presence of a hotspot beneath the North American Plate, categorizing it as **intraplate volcanism**.

Identifying Vesuvius' Volcanism

Vesuvius in Italy is a well-known volcano formed due to the subduction of the African Plate beneath the Eurasian Plate. This type of tectonic setting is characteristic of **convergent plate boundaries**.

Identifying Deccan Plateau's Volcanism

The Deccan Plateau in India is known for extensive flood basalt eruptions that occurred due to volcanic activity related to a hotspot during the late Cretaceous period. This is an example of **intraplate volcanism**.

Identifying Mount Etna's Volcanism

Mount Etna is located on the east coast of Sicily, Italy, and is one of the most active volcanoes in the world. It is associated with the convergent boundary between the African and the Eurasian plates, making it part of a **convergent plate boundary** region.

Key concepts

Convergent Plate Boundaries

Convergent plate boundaries are tectonic zones where two plates move towards each other and collide. This often results in one plate being forced beneath the other, a process known as subduction. Such interactions typically create dramatic geological features like mountain ranges, earthquakes, and especially volcanic activity.
Volcanoes at convergent boundaries can be very explosive due to the thick, viscous magma formed by partially melted subducted oceanic crust, which contains large amounts of volatile compounds. These conditions lead to cataclysmic eruptions.

• Examples: The Cascade Range with Mount St. Helens, and Mount Etna in Sicily.
• Characteristics: High-viscosity lava, explosive eruptions.

Volcanoes at these boundaries often form a chain known as a volcanic arc. One of the most well-known examples of such an arc is the "Ring of Fire", which encircles the Pacific Ocean and includes many active volcanoes.
At these boundaries, the interaction between plates also generates significant seismic activity, contributing to the complexity of these regions.

Divergent Plate Boundaries

Divergent plate boundaries occur where two tectonic plates are moving apart from each other. This movement creates gaps which allow magma from the mantle to rise to the Earth's surface, leading to volcanic activity. Over time, this activity can form new crust as the magma cools and solidifies, contributing to the expansion of ocean basins and the creation of mid-ocean ridges.
One of the most prominent examples on land is the East African Rift, where the African plate is splitting into smaller plates. This tectonic activity can lead to the formation of rift valleys and associated volcanic features.

• Examples: The Mid-Atlantic Ridge and the East African Rift.
• Characteristics: Less violent eruptions, mainly basaltic lava flows.

Volcanoes created in these zones generally feature effusive eruptions, where lava flows out steadily and quietly rather than explosively. This happens because the magma is usually very fluid, which means it doesn't trap gases, preventing pressure buildup. These regions are crucial for understanding plate tectonics as they demonstrate the process of seafloor spreading.

Intraplate Volcanism

Intraplate volcanism occurs within a tectonic plate rather than at a plate boundary. This type of volcanism is often linked to mantle plumes or "hotspots," which are areas where hot material rises through the mantle from great depths. As the plate moves over the stationary hotspot, a chain of volcanoes can form, resulting in features like volcanic islands or large plateaus.
Hawaii's Kilauea and Yellowstone are prime examples of intraplate volcanism, seen as the Pacific and North American plates move over their respective hotspots.

• Examples: The Hawaiian Islands and Yellowstone.
• Characteristics: Shield volcanoes, effusive eruptions in Hawaii, and calderas like those found in Yellowstone.

The Deccan Plateau provides another classic instance, shaped by ancient volcanic activity linked to a hotspot. These features remind us that volcanic activity is not confined solely to the boundaries where tectonic plates meet, but can occur far from them due to dynamic processes occurring within Earth's mantle.