Photos: Chile volcano eruption

The Calbuco volcano erupts near Puerto Varas, Chile, Wednesday, April 22, 2015 for the first time in 42 years.

FILE - In this June 17, 2014, file photo, Dr. Mehmet Oz, vice chairman and professor of surgery, Columbia University College of Physicians and Surgeons, testifies on Capitol Hill in Washington. (AP Photo/Lauren Victoria Burke, File)

Dr. Oz: We will not be silenced

Dr. Oz is fighting back against critics who are trying to get him removed from a faculty position at Columbia University.