Final answer:
The word that best summarizes the tone of the passage is panicked.
Step-by-step explanation:
The word that best summarizes the tone of the passage is panicked. The use of words such as 'warning,' 'terrific velocity,' and 'blazing mass' create a sense of urgency and fear, indicating a panicked mood. Additionally, the description of the crowded cities, lit shipyards, and crowded ocean all contribute to the frantic atmosphere. A dash is often used to emphasize or set off an appositive phrase that adds explanatory or clarifying information to the noun that precedes it. In the sentence provided, the dash introduces an appositive that defines “sordid materialism” as the act of accumulating steel structures simply to fulfill the American desire for extremeness in everything.