Topic 3: Earth's Systems

UCAR: The Geosphere

Ducksters: Composition of the Earth

Geography4Kids: A Big Ball of Life

National Geographic: Acid Rain, explained

USGS: The Fundamentals of the Water Cycle

NOAA: Water Cycle

UCAR: Earth's Atmosphere (and at least two layers of the atmosphere)

National Geographic: The Ozone Layer

Beavers and the Biosphere

Beavers and the Hydrosphere