Mount Terror is a large basaltic shield volcano that forms the eastern part of Ross Island. It has an elevation of 3230 meters (10597 feet). It has numerous cinder cones and domes on the flanks of the shield and is mostly under snow and ice. It is the second largest of the three volcanoes which make up Ross Island and is somewhat overshadowed by its neighbor, Mount Erebus.

The rocks at the summit have not been studied, but lower areas have been studied and rocks from those areas range from 0.82 to 1.75 million years old. Mount Terror shows no signs of volcanic activity more recent than that.

The first ascent of Mount Terror was made by a New Zealand party in 1959.