In which locations can convection currents form?

Convection currents can indeed form in a freshwater lake, primarily due to the temperature differences between the warmer surface water and the cooler water below. As the surface water is heated by the sun, it becomes less dense and rises. This movement allows the cooler, denser water from below to sink, creating a continuous cycle of circulating water. This process helps distribute heat throughout the lake, resulting in a balanced temperature profile and providing a dynamic environment for aquatic life.

In contrast, while convection can occur in certain environments, a sand dune lacks the necessary fluid medium, as it consists of solid particles that do not exhibit the same ability to circulate as liquids or gases. Outer space, being a near-vacuum, does not support convection because it lacks a medium to conduct heat and therefore cannot facilitate the movement of particles. Earth's mantle, while it does exhibit convection currents due to the slow movement of the semi-solid rock materials under high temperatures and pressures, is not primarily represented in this question's focus on locations where convection is easily observed and understood, such as in a freshwater lake.