Water Cycle and Freshwater Sources

The video reviews Earth's water distribution, highlighting that 75% of the planet is covered in water, with 97% being saltwater and only 3% freshwater. Of the freshwater, two-thirds is frozen in glaciers and ice caps, leaving only 1% of all Earth's water usable by humans. The water cycle plays a crucial role in replenishing freshwater supplies. The video also explains how oceans became salty through weathering and erosion over millions of years. Finally, it identifies the main sources of freshwater, including glaciers, groundwater, lakes, rivers, and the atmosphere.

What percentage of Earth's water is freshwater?

• 50%

• 25%

• 3%

• 97%

Where is the majority of Earth's freshwater found?

• Atmosphere

• Rivers

• Oceans

• Glaciers and ice caps

What percentage of Earth's total water is usable by humans?

• 50%

• 25%

• 10%

• 1%

Why don't we run out of freshwater despite its limited availability?

• Desalination

• Water cycle

• Increased rainfall

• Reduced usage

What role do oceans play in the water cycle?

• They prevent water pollution

• They are the main source of evaporation

• They increase rainfall

• They store all freshwater

How did the ocean become salty over time?

• Volcanic eruptions

• Weathering and erosion

• Human activities

• Animal waste

What process contributes to the ocean's salinity by leaving salt behind?

• Condensation

• Evaporation

• Precipitation

• Infiltration

Which of the following is NOT a major source of freshwater?

• Deserts

• Glaciers

• Groundwater

• Lakes

What is the second largest source of freshwater on Earth?

• Groundwater

• Atmosphere

• Lakes

• Rivers

Which component of the atmosphere is crucial for the water cycle?

• Carbon dioxide

• Oxygen

• Water vapor

• Nitrogen