If we knew what caused it, it wouldn't be IDIOPATHIC! If and when a cause is found, it will have a (probably mechanistic) name, and will no longer be called idiopathic.
The Ebright Road benchmark (NGS disk EBRIGHT AZI) was found to be 447.85 feet above sea level. Many people consider Centreville, Delaware to be the highest point in the state; however, a benchmark at Centreville has an elevation of only 445.58 feet making the Ebright Azimuth disk more than two feet higher.
Ryan Ozawa has it right - the summit benchmark of Mauna Kea reads 13,796 feet, although some more recent satellite measurements have indicated 13,802 feet. That's unquestionably the highest natural point in Hawaii. The enclosure for the Gemini Observatory telescope located a few hundred feet from the summit actually reaches higher than the summit, so the highest manmade point in Hawaii would be the top of Gemini's dome, at somewhere above 13,820 feet.