Snake Butte is located 10 miles south of Harlem on the northern part of the Ft. Belknap Reservation. Travelers in the Harlem area are treated to a view of Snake Butte between the Little Rockies and the Bear Paws (Bear's Paw Mountains) on the southern horizon. The Little Rockies are actually 25 miles south of Snake Butte and the Bear Paws begin 15 miles to its southwest. A portion of the Bear Paws can be seen on the right side of the photo above. The geology of Snake Butte is fascinating, but it is also an important spiritual place for Native Americans, and played a major role in one of the biggest construction projects in Montana's history.
A Spiritual Place . . .
High places that stand above the prairie are often considered sacred to Native Americans. Snake Butte is such a place, and one of the ways it has been used by Native Americans is for the spiritual experience called a "vision quest". Although every tribe has different beliefs and ceremonies, the quest is an intensely private experience that often begins by cleansing the body through sweat-lodge purification. Next, the person withdraws to a secluded location for three to four days, where they fast and pray in order to seek a vision experience. The Snake Butte area is also home to the Ft. Belknap bison herd.
Volcanism in North-Central Montana . . .
The reason the Snake Butte is a high place has to do with its connection to an ancient center of volcanic activity. It is made of igneous rock (formed as magma or lava hardens). In this case the magma hardened underground, therefore Snake Butte is classified as an intrusive igneous formation. The magma that became Snake Butte originated from the same volcanic center that formed the Bear Paws. On the other hand the Bear Paws are an extrusive igneous formation, formed as lava cooled on the surface. The Bear Paws are the remnants of an area where volcanoes were active 50 million years ago.
In some places magma beneath this volcanic center moved through cracks in surrounding sedimentary rock (dikes) and forced its way between layers of sedimentary rock (sills) where it cooled slowly. This slow cooling gave minerals time to form larger crystals (see photo to right). Click here to see a larger photo. Eventually the crystals grew into each other, forming interlocking grains that give the rock its durability. This appearance (texture) is referred to as course-grained (see photo on right). Granite is the most common type of course-grained igneous rock. The granite-like rock that Snake Butte is made of is known as "syenite". In the millions of years after the magma hardened beneath the surface, less durable sedimentary rock above and around it eroded away and the rock of Snake Butte was exposed. The Bear Paws, the Highwoods, and the mountains between Craig and Cascade are all made of durable igneous rocks.
Columns of Stone . . .
Visitors to Snake Butte will see a feature of igneous rocks called "columnar jointing", which is sometimes present where igneous rock is exposed. Columnar jointing happens when lava or magma shrinks as it hardens, causing it to crack into neat geometric columns. The columns found on the northern and eastern cliffs of Snake Butte are especially large as shown in the photo below. Large columns can also be seen in some places on the top.
Because of its especially durable igneous rock, Snake Butte was an important source of material used to build Ft. Peck Dam in northeastern Montana from 1933-1940. Since most of the rock in eastern Montana is sedimentary rock, which was unsuitable for the dam, the tough syenite of Snake Butte was chosen for the project. The butte's proximity to the Great Northern Railway supported this choice. Rock quarried from Snake Butte was hauled by rail 10 miles into Harlem and then onto the construction site near Glasgow 100 miles to the east.
CLICK HERE to access a blog and photo tour that includes much more information about Snake Butte.
Term: sill
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