Mountains are not closer to the sun than any other point on the Earth's surface. The Earth orbits the sun in a nearly circular path. The axis of the Earth's rotation is tilted with respect to the plane of the orbit, so different parts of the Earth receive more or less direct sunlight at different times of the year. Mountains are formed by the collision of tectonic plates, and are therefore found in areas where the Earth's crust is thicker. The thicker crust means that the geothermal gradient is lower in mountainous areas, so the air temperature at a given altitude is lower than it would be in a thinner-crusted area. In addition, mountains are often covered in snow and ice, which reflects sunlight and further contributes to the cooler temperatures.