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Our Glaciers: Then and Now activity kit helps you see the changes taking place in glaciers around the world. See all our activity kits and classroom activities.

Mature Stage

When the cumulus cloud becomes big, the water in it becomes heavy. It starts to fall out of the cloud. At the same time, cool dry air starts to enter the cloud. Cool air is heavier than warm air. The cool air creates a wind that blows downward. This wind pushes the heavy water to the ground. It starts to rain.

This cloud is now called a cumulonimbus cloud. Lightning and thunder start to occur. The cumulonimbus is now a thunderstorm.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA