Question

Which one of the following is a gently sloping (< 10°) volcanic landform resulting from eruption of basaltic lava?

• A. Shield volcano
• B. Composite volcano
• C. Lava dome
• D. Caldera

Answer 1

The Correct Option is A

The question asks us to identify a volcanic landform characterized by a gentle slope of less than 10 degrees and formed from basaltic lava eruption. Let's evaluate each option to determine the correct answer:

1. Shield volcano: These are large, broad volcanoes with gentle slopes due to low-viscosity basaltic lava that can travel long distances. Typically, the slopes of shield volcanoes are less than 10 degrees, making them fit the description perfectly. Hence, this is the correct option.
2. Composite volcano: Also known as stratovolcanoes, these have steeper profiles and are formed from a combination of explosive eruptions and lava flows, usually involving andesitic or dacitic lava. The slopes are much steeper than 10 degrees, ruling out this option.
3. Lava dome: These occur when viscous lava piles up near the vent, creating a dome-shaped, steep-sided mound. Lava domes have steep slopes, certainly steeper than 10 degrees, eliminating this as a possible answer.
4. Caldera: A caldera forms after the collapse of a volcano's summit following a major eruption, leading to a large crater. They are not characterized by gradual slopes formed by lava flow, so this does not match the question’s description.

Based on the above analysis, the correct choice is the Shield volcano. This type of volcano has the gentle slopes described in the question and is the result of the eruption of low-viscosity basaltic lava.

Conclusion: The gently sloping volcanic landform resulting from basaltic lava is the Shield volcano.