Sometime in the past few million years, collapse at the top of the cave and surface erosion created the natural entrance of Carlsbad Cavern. This opened previously hidden underground cave passageways to the world above for the first time.
The Society of Diagnostic Medical Sonography (SDMS) defines sonography as diagnostic medical procedure that uses high frequency sound waves (ultrasound) to produce dynamic visual images of organs, tissues, or blood flow inside the body. This type of procedure is often referred to as a sonogram or ultrasound scan.
In obstetrics, sonography is used to determine the number, age, and location of a fetus, as well as to check for potential birth defects. It is also used to identify abnormalities in the abdomen, such as liver disease or gallstones. Sonograms can also be used to detect heart disease.