Turf
I don't think they are eventually covered with soil and grass.
To hide them from view.
The thick mass of grass and soil is called the topsoil
It takes about two months for covered grass to die. Covering grass with cardboard and organic mulch is a good way to effectively kill grass and create rich soil at once.
The dirt under grass can be called soil.
A person who studies the grass and soil, etc. is called a Agrostologist
The top layer of soil and grass attached to it is called the "sod." It includes the grass and roots growing in the topsoil, forming a dense mat that can be cut and lifted for transplanting.
Gullies are more likely to form in a field with plowed soil and no plants because the soil is loose and more susceptible to erosion from runoff. A field covered with thick grass helps prevent gully formation by reducing the speed of runoff and holding the soil in place with its roots.
Yes, bare soil tends to absorb more solar heat than grass-covered soil due to its darker color and lower albedo (reflectivity). The dark surface of the bare soil absorbs more sunlight, warming it up more quickly than the lighter-colored grass, which reflects more sunlight. This difference in heat absorption can lead to significant temperature variations between the two types of surfaces.
In the latter.
The uppermost layer of soil that is covered in grass and the roots that hold it together. This layer can be cut and removed in slabs or rolls.
Gullies would be more likely to form in a field with plowed soil and no plants because the soil is more exposed and vulnerable to erosion from water flow. In contrast, a field covered with thick grass can help reduce erosion by holding the soil in place with its roots and providing protection from rainwater runoff.