A **giant kettle** is an erosional cavity, roughly cylindrical or pit-shaped, found in the beds of some rivers, especially in areas of hard rock such as granite.
**How does it form?**
1. **Irregularities:** The process begins with small irregularities or hollows in the rock surface of the riverbed.
2. **Abrasion:** The water current traps pebbles, sand, and other hard sediments. The swirling motion of the current causes these materials to act as drilling tools, eroding and deepening the initial hollow through abrasion.
3. **Deepening:** Over time, the cavity grows larger and deeper, acquiring its characteristic "kettle" or "pot" shape. The fragments broken off from the parent rock contribute to this erosive process.
**Characteristics:**
* They are typically found in the upper reaches of rivers, where the current has greater velocity and energy.
* The rock in which they form is usually hard and durable, such as granite or sandstone.
* Their size can vary from a few centimeters to several meters in diameter and depth.
* They often form in groups along the riverbed.
* When the river slows or dries up, the potholes are exposed, revealing their smooth, rounded walls.