Agathla Peak is a peak south of Monument Valley

Monument Valley

Monument Valley is a region of the Colorado Plateau characterized by a cluster of vast sandstone buttes, the largest reaching above the valley floor. It is located on the northern border of Arizona with southern Utah , near the Four Corners area...

, Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

, over 1500 feet (457 meters) high. It is 7 miles (11.3 km) north of Kayenta

Kayenta, Arizona

Kayenta is a census-designated place which is part of the Navajo Nation and is in Navajo County, Arizona, United States. The population was 5,189 at the 2010 census. Kayenta is located south of Monument Valley and contains a number of hotels and motels which service visitors to Monument...

 and is visible from U.S. Route 163

U.S. Route 163

U.S. Route 163 is a U.S. Highway that runs from US 160 northward to US 191 in the U.S. states of Arizona and Utah. The southernmost of its length is within the Navajo Nation. The highway forms part of the Trail of the Ancients, a National Scenic Byway...

. The English designation Agathla is derived from the Navajo name meaning 'much wool', apparently for the fur of antelope and deer accumulating on the rock. It is considered sacred by the Navajo.

Agathla Peak is an eroded

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 volcanic plug

Volcanic plug

A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when magma hardens within a vent on an active volcano. When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it, and this can sometimes lead to an...

 consisting of volcanic breccia cut by dikes

Dike (geology)

A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...

 of an unusual igneous rock called minette

Minette

Minette may refer to:*the Haitian actress Minette *Henrietta Anne of England also nicknamed Minette*Minette is an archaic rock term used to locally describe a particular type of lamprophyre...

. It is one of many such volcanic diatreme

Diatreme

A diatreme is a breccia-filled volcanic pipe that was formed by a gaseous explosion. Diatremes often breach the surface and produce a tuff cone, a filled relatively shallow crater known as a maar, or other volcanic pipes.- Word origin :...

s that are found in Navajo country of northeast Arizona and northwest New Mexico. Agathla Peak and Shiprock

Shiprock

Shiprock is a rock formation rising nearly above the high-desert plain on the Navajo Nation in San Juan County, New Mexico, USA. It has a peak elevation of above the sea level. It lies about southwest of the town of Shiprock, which is named for the peak...

 in New Mexico are the most prominent. These rocks are part of the Navajo Volcanic Field, in the southern Colorado Plateau

Colorado Plateau

The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...

. Ages of these minettes and associated more unusual igneous rocks cluster near 25 million years.