Creating Lake-Effect Snow
Situated on Lake Erie, the city of Buffalo, New York, is one of the snowiest cities in the United States. Like other cities on large lakes, it is subject to a phenomenon called lake-effect snow. Water retains heat, so lake water is often warmer than the air. In the lake effect, cold air moves over warmer lake water, initiating a process that can produce large snowstorms. Moisture from the lake evaporates into the cold air, warming it. Because warm air is less dense than cold air, it begins to rise. As it rises and moves away from the lake, it cools down. As the air cools, moisture condenses and forms into clouds. If the temperature is cold enough, the moisture falls to the ground as snow.
What is the main, or central, idea of the passage?
A In the lake effect, warm air, which is lighter than cold air, rises and moves away.
B Buffalo, New York, gets more snow than most cities in the United States.
C When cold air moves over the warmer water of a lake, lake-effect snow can be produced.
The correct answer and explanation is:
The correct answer is C: “When cold air moves over the warmer water of a lake, lake-effect snow can be produced.”
Explanation:
The passage focuses on explaining the process of lake-effect snow, particularly in the city of Buffalo, New York, which is located on Lake Erie. The central idea is the scientific explanation behind the phenomenon that occurs when cold air moves over a warmer lake, which then leads to the production of snow. This process involves several stages, starting with cold air moving over the relatively warmer lake water. The warmer water causes the cold air to warm up, and as the air rises, it moves away from the lake. As it rises, the air cools down, and the moisture within it condenses to form clouds. If the temperature is low enough, this condensation results in snow.
The passage emphasizes the relationship between the lake and the atmosphere and how this interaction produces large snowstorms, a specific weather phenomenon that happens near large lakes. It also highlights why Buffalo is one of the snowiest cities in the U.S., as it is directly affected by this process.
Option A discusses the movement of warm air, which is part of the explanation, but it does not capture the overall process of snow formation. Option B mentions that Buffalo gets a lot of snow, which is a supporting detail, but it is not the main focus of the passage. Therefore, option C correctly summarizes the central idea of how lake-effect snow occurs.