Scary moment at the race track Tuesday ... Dale Earnhardt Jr.'s 18-year-old niece was involved in a horrific crash -- but miraculously escaped uninjured!!
It all went down at a USAC Racing event at Red Dirt Raceway in Oklahoma ... where Karsyn Elledge -- whose mom, Kelley Earnhardt Miller, is Jr.'s older sister -- flipped her sprint car multiple times over a barrier and fencing.
Elledge was coming down turn 3 at the track when she lost control ... causing her car to get airborne and tumble several yards OVER a wall before coming to a stop.