The first two volcanoes are both heavily incised by cirques, while Mount Frakes is better preserved and has a 4 kilometres (2.5 mi) wide caldera at its summit.

The volcanoes consist mainly of basalt, trachyte and phonolite in the form of lava flows, scoria and hydrovolcanic formations.

Volcanic activity here is linked to the West Antarctic Rift system, which is responsible for the formation of a number of volcanoes in the region.

The mountain range lies in eastern Marie Byrd Land, Antarctica,[1] about 250 kilometres (160 mi)[2] from the Bakutis Coast.

[5] The Crary Mountains form a drainage divide for the West Antarctic Ice Sheet;[9] they dam it, which is thus higher on the southwestern side of the range.

[6] Mount Steere is heavily dissected,[12] bears evidence of former glaciation in the form of moraines[13] and cirques have been eroded into its northern and northeastern flanks.

[16] Boyd Ridge is smaller than the other three volcanoes[5] and located southeast of Mount Frakes and reaches an elevation of 2,375 metres (7,792 ft).

[18] Echo and magnetic sounding have imaged the root of the Crary Mountains in the West Antarctic Ice Sheet, finding that the underlying terrain is steep and flanked by narrow troughs.

[20] Cenozoic volcanism in Marie Byrd Land is related to the West Antarctic Rift and has been explained by the activity of a mantle plume.

This plume either underlies Marie Byrd Land and its volcanoes, or it rose to the surface before Antarctica separated from New Zealand during the middle Cretaceous and induced volcanism across the continental borderlands of the Southwest Pacific.

[6] This volcanism manifests itself with 18 large and numerous smaller volcanoes, which occur in groups, rows or as solitary systems in Marie Byrd Land.

The larger centres have produced phonolite, rhyolite, trachyte and rocks with intermediate compositions, and reach heights of over 3,000 metres (9,800 ft) above sea level.

[12] West Antarctica has been subject to glaciation since the Oligocene, where a perhaps local ice cap or snow deposit existed at Mount Petras.

Volcanoes erupting through ice leave specific geologic structures which can be used to reconstruct the timing and extent of past glaciations.

[28] Geologic evidence at the Crary Mountains implies that a substantial West Antarctic Ice Sheet existed during the Miocene, and that fluctuations in its size may have stressed the crust and modulated the activity of volcanoes in its area.

Prominent mountain 3,500 metres (11,500 ft) high standing 4 nautical miles (7.4 km; 4.6 mi) north-northwest of Mount Frakes.

Named by US-AC AN for Lawrence A. Frakes, USARP geologist who worked three summer seasons in the Falkland Islands and Antarctica, 1964-65 through 1967–68.

Named by US-ACAN for Paul W. Morrison, United States Navy, hospital corpsman at the South Pole Station in 1974.

An ice-covered ridge, 22 nautical miles (41 km; 25 mi) long, which extends in an east–west direction and forms the south end of the Crary Mountains.

Named by US-ACAN for William E. Runyon, United States Navy, construction electrician at the South Pole Station in 1969 and 1974.