Hopi Buttes volcanic field is amonogeneticvolcanic field located on theColorado Plateau mostly on theNavajo Reservation around the town ofDilkon in northeastern Arizona north ofHolbrook.
The volcanic field covers an area of approximately 965 square miles (2,500 km2) and contains about 300maars anddiatremes.[1]
The erosional exposure of the deposits varies with those in the eastern portion exhibiting the shallowly eroded maar deposits and those in the western portion the more deeply eroded feeder diatremes. The maars result from explosive interaction of the hot diatreme material with the groundwater system and result in a mixture of volcanictuff material and sediments of theMiocene–Pliocenelacustrine sediments of theBidahochi Formation. In the western portion of the field the buttes consist of the feeder diatremes ofmonchiquite andnepheline syenitemagmas.[2]
Most of the volcanic activity occurred between 8.5 and 6 million years ago, with the most recent dated at 4.2 million years ago.[3]
| Name | Elevation | Location | Last eruption | |
| meters | feet | Coordinates | ||
| Coliseum Maar[4] | 1,811 | 5,940 | 35°24′N110°06′W / 35.400°N 110.100°W /35.400; -110.100 (Coliseum Maar) | |
| Morale Claim Maar[5][6] | 1,859 | 6,100 | 35°30′N111°00′W / 35.500°N 111.000°W /35.500; -111.000 (Morale Claim Maar) | |
35°28′03″N110°11′32″W / 35.46750°N 110.19222°W /35.46750; -110.19222
