Using paper patterns, students are able to construct a model that depicts Karst topography, including typical features such as caves, limestone bedrock, sink holes, and springs. The accompanying Teachers Guide provides extensive background information about the dissolutional processes that form caves. Information is also provided about unique animals found in caves and the importance of understanding ... Full description.

The European Space Agency's Mars Express Satellite has recorded images in three different bands of the southern polar cap of Mars, which show both frozen carbon dioxide and water ice. The images are presented with a brief caption and links to other Mars Express imagery and status reports. Full description.

This site uses a picture of a covered swimming pool as an example of a watershed and describes real-world watersheds and their processes, including precipitation, infiltration, evaporation, transpiration, and storage. Links to an interactive rainfall calculator and to related websites are included. Full description.

This site describes how snow and ice runoff become surface water and emphasizes how runoff from snowmelt is a major component of the global movement of water. A hydrograph from the U.S. Geological Survey shows a four-year time series of streamflow and illustrates how runoff from snowmelt affects the daily mean values, particularly at certain times of the year. Full description.

This interactive site features games, animations, and teachers' materials intended to introduce younger students to climate change. There is information about what climate change is, the difference between weather and climate, and the greenhouse effect. There are also materials on the climate system, ancient climates, and how scientists investigate climate. Other topics include discussions of whether ... Full description.

The purpose of this activity is to build an instrument that can be used to measure water temperature. Students construct a soda-bottle thermometer, which is similar to the thermometer used by GLOBE schools. Both are based on the principle that most substances expand and contract as their temperature changes. This experiment also demonstrates the principle of heat transfer. The intended outcome is ... Full description.

The purpose of this activity is to construct a model that will provide students with a visual representation of parts per billion. Students work in teams to construct cubes of different volumes and to compare them to get a feel for parts per million by volume and parts per billion by volume. The intended outcome is that students gain a feeling for the small quantities of gases, such as ozone, present ... Full description.

The Antarctic ice sheet changes in size over the course of a year. When it is summer in the southern hemisphere, the ice sheet decreases in size. As the ice sheet melts, it releases fresh water into the ocean. In the southern winter (our summer), the ice refreezes, drawing fresh water out of the surrounding ocean, leaving the salt behind. These seasonal changes in the ice sheet are examined in this ... Full description.

Students in this lesson will be introduced to the concept of tides and tidal forces. By viewing a related applet which visualizes the relationship between the Earth, moon and tides, students will gain an understanding of why the Earth experiences tides. In the process they are asked to observe and explain how the relative positions of Earth, the moon, and the sun are responsible for the moon phases, ... Full description.

This website presents the story of Comet LINEAR, which broke apart in 2000, revealing what many scientists thought all along - water in Earth's oceans could have come from outer space. The article discusses findings from the breakup of Comet LINEAR and the possibility of water in its composition. Full description.