Formed when caves can no longer support the dirt above it.

Collapse dolines.

Explanation:

A doline is a special type of geological depression characteristic of karst reliefs. These reliefs are formed by the chemical weathering of rocks made of minerals that are soluble in water. In general, dolines are found in places where rocks are composed of limestone and clay in different proportions. When the calcium carbonate of limestone gets in contact with the rainwater, turns into calcium bicarbonate, which is soluble in the presence of water. Clay then deposits in lower areas originating the dolines or depressions.

Dolines might be formed by dissolution (the soil is dissolved in pluvial water that first flood and then infiltrate) or by collapsing. Collapse dolines occur because first, soluble material in lower layers formes a cavity underground. Soluble material flow to lower areas making a place to a cavity or hole under the ground. It gets bigger with time as the material in the bottom keeps being removed. It reaches a point in which the cave can no longer support the roof material, such as rocks, soil, and vegetables, and ends collapsing.  

metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). the change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. i hoped i !