Question

Is seismic risk greater in a town on the west coast of South (B) America or in one on the east coast? Explain your answer.

Short answer

The seismic risk is greater in a town on the west coast of South America compared to one on the east coast. This is because the west coast is near the converging boundary of the South American Plate and the oceanic Nazca Plate, creating subduction zones and the Andean Mountain Range, leading to higher tectonic activity and seismic risk. The east coast, however, is located further from active tectonic boundaries and experiences a lower seismic risk due to comparatively less tectonic activity.

Step-by-step solution

Understand the tectonic setting of South America

South America is located in the western hemisphere and is part of the South American Plate. On its western edge, the South American Plate is converging with the oceanic Nazca Plate. This causes the formation of the Andean Mountain Range and various subduction zones along the west coast, where the oceanic plate is being forced beneath the continental plate. On the east coast, the South American Plate is moving away from the African Plate, forming the South Atlantic Ocean. This area has less tectonic activity compared to the west coast.

Compare seismic risks on the west and east coasts

Due to the tectonic setting discussed above, the west coast of South America experiences more earthquakes and volcanic activity. The subduction zones create a high seismic risk, as they are areas of frequent earthquakes. On the other hand, the east coast has a relatively lower seismic risk. It lies further from any active tectonic boundaries and does not have a history of significant earthquake or volcanic activity.

Conclude which coast has greater seismic risk

Based on the analysis of the tectonic settings and seismic activity, it can be concluded that a town located on the west coast of South America would have a greater seismic risk compared to one on the east coast. This is due to the large-scale tectonic processes occurring on the western edge of the continent, making it more prone to earthquakes and associated hazards.

Key concepts

Tectonic Setting

The tectonic setting of South America is intrinsically linked to the seismic risk faced by the continent. South America sits on the South American Plate, which interacts with several other tectonic plates, most notably the Nazca Plate to the west. The movement of these plates shapes the landscape and influences the likelihood of seismic events.

On the west coast, the convergence between the South American Plate and the Nazca Plate has created the Andes mountains, a classic example of mountain formation at convergent plate boundaries. This region's tectonic activity also results in frequent earthquakes. The east coast, by contrast, is stable with fewer earthquakes because it sits on the interior of the South American Plate, which is moving away from the African Plate, thus experiencing less tectonic stress and associated risks.

Subduction Zones

Subduction zones are areas where one tectonic plate slides beneath another, often triggering significant geological activity. Along the west coast of South America, the oceanic Nazca Plate is being subducted under the continental South American Plate. This process not only gives rise to mountain ranges but also to deep oceanic trenches such as the Peru-Chile Trench.

The interface at these zones is a hotbed for seismic activity, as the two plates interact in a complex dance of stress accumulation and release, often producing powerful earthquakes. Understanding the mechanics and locations of these subduction zones is essential for assessing earthquake risk.

Earthquake Activity

Earthquake activity in South America is primarily concentrated along the west coast due to the interactions at the subduction zones. These earthquakes can range from minor tremors to devastating quakes that can cause widespread damage.

The seismic risk is elevated in regions where the build-up of tectonic stress leads to sudden releases of energy. Urban areas near these zones must plan for earthquakes, reinforcing structures, and implementing strict building codes to minimize the damage from these unavoidable natural events.

Volcanic Activity

Volcanic activity is another manifesting consequence of the subduction processes on the west coast of South America. As the subducted Nazca Plate melts, magma rises and erupts through volcanoes along the Andean volcanic belt. This region is a part of the Ring of Fire, a zone around the Pacific Ocean where a significant number of the world's volcanoes are found and eruptions are common.

Communities near volcanoes need to be prepared for eruptions and have evacuation plans in place, alongside monitoring systems to predict and respond to volcanic activity timely.

Nazca Plate

The Nazca Plate is an important piece of the tectonic puzzle in South America. It is an oceanic plate that lies west of the continent and is moving eastward, towards the South American Plate. Its subduction beneath the continent not only fuels earthquakes and volcanoes but also significantly influences the geography and climate of the region.

The speed and angle at which the Nazca Plate converges with the South American Plate can affect the frequency and intensity of seismic activities, helping scientists predict and prepare for natural disasters.

South American Plate

The South American Plate covers not only the continent of South America but also part of the Atlantic Ocean. While the western margin is characterized by the subduction zone interactions with the Nazca Plate, other boundaries are also active. To the north, the Caribbean Plate and to the southeast, the Scotia Plate interacts with the South American Plate.

However, the seismic risk is not uniformly distributed across the plate due to varying tectonic mechanisms at work. Cities and towns on the plate's western edge face higher seismic risk due to the ongoing subduction processes.