Abismo Guy Collet
The Abismo Guy Collet (SP-090) is the deepest cave in South America, and the deepest in the world that is formed in quartzite. Located in a tepui in northern Brazil near the border with Venezuela, this cave was first explored by cavers in 2006 to a depth of 671 meters.
Mount Adams (Washington)
In the area surrounding Mount Adams, many caves have formed around inactive lava vents. These caves are usually close to the surface and can be hundreds of feet deep and wide. A few of the more well known caves include the Cheese Cave, Ice Cave, and Deadhorse Caves. Cheese Cave has the largest bore of the caves near Adams with a diameter of and a length of over . Ice cave, which is made up of several sections created by several sinkholes, has an ice section that is long and in diameter and noted for its ice formations. From the same entrance, the tube continues another to the west. Deadhorse Cave is a massive network of lava tubes. It the most complex lava tube in the United States with of passage. These caves are all just outside of Trout Lake. These and many other caves in the Trout Lake area were at one time part of a huge system that originated at the Indian Heaven volcanic field. The most obscure caves around Adams are the Windholes on the southeast side near Island Cabin Campground.