I have a mouth, but do not speak; I have a bed, but do not sleep; I can be small or big, thin or wide; And when I’m calm, you can go for a ride. What am I?

This intriguing riddle cleverly describes a natural phenomenon that has shaped landscapes and civilizations for millennia. The answer, a river, perfectly fits each clue. When the riddle mentions a "mouth," it refers to the point where a river empties into another body of water, such as a sea, lake, or larger river. Similarly, the "bed" of a river is the channel that holds the flowing water, a geological feature rather than a place for slumber.

Rivers are incredibly diverse, ranging from narrow, shallow streams to vast, powerful waterways like the Nile or the Amazon, illustrating how they can be "small or big, thin or wide." This variability is influenced by factors such as rainfall, topography, and the surrounding environment. Throughout history, these moving bodies of water have been crucial for transportation, irrigation, and as a source of food and drinking water, supporting countless ecosystems and human settlements.

Finally, the line "when I’m calm, you can go for a ride" points to the recreational and practical uses of rivers. When the current is gentle, rivers offer ideal conditions for activities like boating, kayaking, and even rafting, providing both enjoyment and a means of travel. Rivers are dynamic systems, constantly changing and interacting with their environment, making them fascinating and vital components of our planet.