The Arnold Lava Tube System (or Arnold system) is series of lava tubes in Deschutes County, Oregon, in the United States. It is located several miles southeast of the city of Bend. The system starts in the Deschutes National Forest on the northern flank of Newberry Volcano, heads northeast onto BLM land before finally terminating on private property near Horse Ridge. The system acted as a conduit for the lavas from Lava Top Butte that later fed the Badlands rootless shield. The lava flow that created the Arnold system is also referred to as the basalt of Lava Top Butte and is related to the Horse Cave lobe which is a lava flow that created the Horse Lava Tube System. The lava flows of Lava Top Butte, the Badlands, the Horse system, and the Arnold system all have a geologic age around 80,000 years old.