ELI5: Explain Like I'm 5

Residuum (geology)

Residuum in geology means the leftover pieces of rocks and minerals that stay behind after the softer and smaller materials are washed away. Think about making a sandcastle on the beach - when the waves come in and wash away the sand, you might still have some bigger shells or rocks left over. These leftover pieces are like residuum.

In geology, residuum is often found in places where there has been a lot of erosion. This can happen when water, wind, or ice wear away the surface of rock formations. Over time, the softer parts of the rock get worn away, leaving behind harder pieces that make up the residuum.

Scientists can study residuum to learn about the history of the area where it was formed. For example, they might examine the types of rocks and minerals in the residuum to get an idea of what the area used to look like millions of years ago. By studying residuum, scientists can gain a better understanding of how the Earth has changed over time.