Question

Which type of volcano, shown above, is made entirely of tephra? A) shield C) cinder cone B) caldera D) composite

Short answer

Cinder cone volcanoes are made entirely of tephra.

Step-by-step solution

Understand the Term 'Tephra'

Tephra refers to the fragments of volcanic material that are ejected into the air during an eruption. These materials can vary in size from tiny particles of volcanic ash to large boulders.

Know the Types of Volcanoes

There are several types of volcanoes, but for this exercise, focus on these: shield, cinder cone, caldera, and composite volcanoes. Each has unique characteristics based on their formation and eruption style.

Identify the Characteristics of a Cinder Cone Volcano

Cinder cone volcanoes are small, steep-sided volcanoes that are built from the accumulation of tephra, such as volcanic ash, cinders, and bombs. They are often shorter in height compared to other types of volcanoes.

Eliminating Other Types of Volcanoes

- Shield volcanoes have gentle slopes and are built from fluid lava flows, not tephra. - Calderas are large, crater-like forms that occur after a massive eruption and collapse, not specifically with tephra. - Composite volcanoes (also known as stratovolcanoes) are built from alternating layers of lava and other volcanic debris, not solely tephra.

Conclusion

Based on the characteristics listed, cinder cone volcanoes are the ones predominantly made entirely of tephra, due to their formation from volcanic fragments.

Key concepts

Tephra

Tephra is a term used to describe the fragmented pieces of rock and ash that volcanoes eject into the atmosphere during eruptions. These materials can range significantly in size, from very fine ash particles that can travel great distances in the wind, to large rocks known as volcanic bombs.
Volcanoes release tephra during explosive eruptions, when magma is fragmented by escaping gases and pressure. The size and type of tephra produced depend on the composition of the magma and the force of the eruption.

• Volcanic ash consists of tiny particles that can cause respiratory issues and damage machinery when airborne.
• Lapilli are small, pebble-sized fragments that can accumulate around the volcano.
• Volcanic bombs are larger, boulder-sized pieces, which can cause massive damage upon impact.

The accumulation of tephra can dramatically alter landscapes around volcanoes, creating new landforms and affecting ecosystems.

Types of Volcanoes

Volcanoes are fascinating natural structures that come in different shapes and sizes, each with its unique formation process and eruption style. The most common types of volcanoes are:

• Shield Volcanoes: Known for their broad, gentle slopes, shield volcanoes are formed by the flow of highly fluid lava. These eruptions are typically less explosive.
• Cinder Cone Volcanoes: These are the simplest type of volcano. They have steep sides and are built entirely of tephra, such as ash and volcanic bombs, which accumulate around the vent.
• Composite or Stratovolcanoes: Characterized by a classic volcano shape, they have layers of hardened lava, tephra, and volcanic ash. They often produce powerful and explosive eruptions.
• Calderas: Large, basin-like depressions that form after a volcano empties its magma chamber in a massive eruption, leading to the collapse of the volcano's surface.

Understanding the different types of volcanoes helps in predicting their behavior and potential hazards.

Volcanic Eruptions

Volcanic eruptions are incredible geological events that occur when magma from within the Earth's crust breaks through the surface. These eruptions can vary greatly in their magnitude and behavior.
Eruptions are categorized based on their explosiveness and the materials they emit. The key factors that influence an eruption include the type of magma, the amount of trapped gases, and the presence of water.

• An effusive eruption, typical of shield volcanoes, releases runny lava with low gas content, creating gentle lava flows.
• Explosive eruptions release large quantities of ash, tephra, and volcanic gases, often producing towering columns of ash and pyroclastic flows.
• Other types include phreatomagmatic eruptions, caused by the interaction of water and magma, leading to steam explosions.

Studying volcanic eruptions is crucial for mitigating risks and understanding their impact on the environment and human society.