Squeaks and I live close to a river, and it’s always exciting to watch the water rush by. Sometimes, people even go fishing there! Like most rivers, it flows downhill along the ground. But did you know that some rivers flow right off cliffs? These are called waterfalls!
A waterfall happens when a river flows over the edge of a cliff. One amazing example is Angel Falls in Venezuela, South America. It’s the tallest waterfall in the world, standing almost 1000 meters high! That’s taller than the tallest building!
Waterfalls start as regular rivers with lots of water flowing in one direction. When the river reaches a cliff, the water flows over the edge, creating a waterfall. But here’s something cool: the river actually helps build the cliff!
Underneath the river, there are layers of rock. Some layers are hard, while others are softer, like a cake with many layers. The water flows over these layers, and over time, it wears away the softer layers. This process is called erosion.
Erosion happens when water wears away rocks. It’s easier for water to erode soft rocks than hard ones, just like it’s easier to smash a sandcastle than a brick. As the water erodes the soft rock, it takes away little pieces until the soft layer is gone. This creates a cliff between the hard rock layers.
This process takes a very long time, sometimes millions of years! When the soft rock is gone, the water flows over the top of the cliff and falls straight down, forming a waterfall.
Angel Falls is especially tall because of the way the water and rock interact. The land around Angel Falls has layers of very soft rock that erode easily and layers of very hard rock that hardly erode at all. This big difference in erosion has helped create the tallest waterfall in the world!
Thanks for exploring waterfalls with us on SciShow Kids! If you have questions about waterfalls, erosion, or anything else, ask a grown-up to help you leave a comment or send us an email at [email protected]. See you next time at the fort!
Build Your Own Waterfall: Gather some materials like a tray, sand, small rocks, and a cup of water. Create a small hill with the sand on one side of the tray. Place the rocks on top of the sand hill to represent hard rock layers. Slowly pour water from the cup over the hill and watch how the water flows. Observe how the sand (soft rock) erodes away while the rocks (hard rock) stay in place. Discuss with a friend or family member how this is similar to how real waterfalls are formed.
Waterfall Adventure Walk: Next time you go for a walk in a park or near a stream, look for places where water flows over rocks or small ledges. Imagine how these small flows could become waterfalls over a long time. Take a notebook and draw what you see. Can you find any signs of erosion, like smooth rocks or small cliffs? Share your drawings and observations with your class or family.
Question Time: Think about why some waterfalls are taller than others. Discuss with a friend or family member: What do you think would happen if the rocks under a waterfall were all the same hardness? Would the waterfall still form? Why or why not? Use what you learned about erosion to explain your ideas.
