Sinkhole also form in high and dry places in specific locations. Sinkholes that capture drainage can hold it in large limestone caves. These caves may drain into tributaries of larger rivers. The formation of sinkholes involves natural processes of erosion or gradual removal of slightly soluble bedrock (such as limestone) by percolating water, the collapse of a cave roof, or a lowering of the water table. Sinkholes often form through the process of suffosion. For example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void. Occasionally a sinkhole
The Heart Is a Lonely Hunter (Once Upon a Time) that Graham helped fill a void for her character, commenting that his loss "was not easy for [Regina]. That’s why, when she crushes his heart, there’s a tear coming out of her eye. She didn’t want to do it, but she had no choice — almost like how she had no choice to kill her father. I’m not saying I agree with it, but for the character, it’s what she had to do." Parrilla also cited "The Heart Is a Lonely Hunter" as the first episode where viewers see "how the two worlds collided," a reference to Regina's ability to