Tie a large knotted rope to a mid sized playground slide. Encourage the children to climb up the slide using the rope and they go. Remind them to turn around before climbing back down the stairs. The children really like to be able to walk up the slide for a change. Baking soda, vinegar, red food coloring, play sand or dirt.
Teachers can introduce the concept of volcanos at a group gathering.
First read a book on the subject, and then ask the children what they know about volcanos. Then you can tell the children that you are going to make your very own volcano in the sand. When they are outside, have the kids form a volcano with sand or dirt, leaving a hole in the top for the materials. For best results, add red food coloring to the vinegar before you pour it. Books about various activities in the world, such as tornadoes, glaciers, avalanche, volcanos, thunder, floods etc.