Question

Distinguish among active, dormant, and extinct volcanoes. (F)

Short answer

Active volcanoes are currently erupting or showing signs of imminent eruption, characterized by regular eruptions and signs like minor earthquakes or gas emissions. Dormant volcanoes are not erupting but could potentially erupt in the future, as they are in a period of inactivity known as dormancy. Extinct volcanoes have not shown signs of activity for thousands or millions of years and are considered highly unlikely to ever erupt again, often due to a lack of a magma chamber or lava source. The main difference among these types of volcanoes lies in their activity level.

Step-by-step solution

1. Definitions

The first step is to understand what each of these terms mean: -A 'Active' volcano refers to a volcano that is currently erupting or showing signs of erupting soon. -A 'Dormant' volcano is one that is not currently active (it's not erupting), but scientists believe it could erupt again. Dormancy is like a volcano’s sleep. -An 'Extinct' volcano is a volcano that scientists consider highly unlikely to erupt again, either because it’s been thousands of years since it last erupted or because it no longer has a lava supply.

2. Active Volcano Characteristics

Active volcanoes are characterised by regular eruptions, with some erupting almost continuously, while others erupt frequently or occasionally. Active volcanoes may also exhibit some signs of upcoming eruptions such as minor earthquakes, emission of steam or gas, and changes in the shape or color of the volcano.

3. Dormant Volcano Characteristics

Dormant volcanoes are not currently erupting. They are typically quiet and do not show signs of upcoming eruptions. However, dormant volcanoes are not entirely safe, as they could still erupt in the future, often with very little warning.

4. Extinct Volcano Characteristics

Extinct volcanoes have not shown signs of activity for thousands or even millions of years and are believed to be unlikely to erupt again in the future. They may be eroding away and do not have a magma chamber or lava source.

5. Comparison

When comparing active, dormant and extinct volcanoes, the key difference lies in their activity level. Active volcanoes are currently erupting or show signs of imminent eruption, dormant volcanoes are not erupting but could potentially erupt in the future, and extinct volcanoes are considered highly unlikely to ever erupt again. By understanding these differences, one can distinguish between active, dormant and extinct volcanoes.

Key concepts

Active Volcano Characteristics

Active volcanoes are akin to Earth's combustion engines, continuously shaping the surface of our planet. These volcanoes can erupt frequently or even persistently over long periods. Some iconic examples include Mount Etna and Kilauea. Active volcanoes are not just about spectacular eruptions. They also emit gases, such as water vapor, carbon dioxide, and sulfur dioxide.

To detect impending eruptions, scientists look for indicators such as:

• Increased seismic activity, like small earthquakes.
• Notable changes in the shape of the volcano, often noted as bulges or movement along its flanks.
• Emissions of steam and gases that might become more intense.
• Visible signs such as lava glow at the summit or fissure vents.

Understanding these warning signs is crucial for early detection and evacuation efforts. Given their unpredictability, active volcanoes require extensive monitoring, ensuring the safety of communities residing in close proximity.

Dormant Volcano Characteristics

Dormant volcanoes can be thought of as being in a state of volcanic 'nap'. They aren’t erupting currently, but they hold the potential for future activity. Unlike active volcanoes, they do not display clear signs of unrest most of the time. Examples include Mount Fuji in Japan and Mount Rainier in the United States.

Dormant volcanoes, despite their present state of calm, still have magma chambers which could become active. Scientists are cautious about them because:

• Their potential to erupt with little to no warning.
• They can change status to 'active' if certain geological conditions are met.
• They are often under surveillance to identify any geological changes that may hint at an upcoming eruption.

Though dormant volcanoes might not be a cause for immediate concern, it is essential to keep them under observation. Their deceptive tranquility can lead to unexpected eruptions, which makes understanding and planning crucial for disaster management.

Extinct Volcano Characteristics

Extinct volcanoes are like relics of the Earth’s fiery past. These geological features have not erupted in over thousands or millions of years, and the probability of them erupting again is extremely low. Famous extinct volcanoes include the Shiprock in New Mexico and the Edinburgh Castle Rock in Scotland.

The reasons for a volcano becoming extinct include the depletion of its magma source or significant tectonic changes over time.

• They often show signs of erosion, with their characteristic volcanic shapes eroded by natural forces.
• No magma chamber or lava source is present, removing the possibility of future eruptions.
• Some extinct volcanoes have been studied to understand the Earth's geological history and evolution.

While they pose no threat of volcanic activity, extinct volcanoes are important for educational and research purposes. They offer a window into past volcanic activity on Earth and help scientists piece together the geological history of our planet.