The character usually reaches two extremes of his personality, which can be cold as an iceberg, or hot, explosive and unpredictable as a volcano.
Explanation:
If an author describes a character in his story as a volcano and an iceberg, it means that the author wants to show how the character's personality is unstable and can reach two extremes quickly in any situation. That's because the character can present himself as someone cold and insensitive, like an iceberg. However, the same character can assume an explosive, unpredictable and hot personality like a volcano.
