The Mission Mountains or Mission Range are a range of the Rocky Mountains located in northwestern Montana in the United States. They lie chiefly in Lake County and Missoula County and are south and east of Flathead Lake and west of the Swan Range. On the east side of the range is the Swan River Valley and on the west side the Mission Valley. The highest point in the Mission Mountains is McDonald Peak at . The range is named for its proximity to the Jesuit St. Ignatius Mission, established in the mid-19th century in what is today St. Ignatius, Montana. Geology The Mission Mountains are composed largely of what is called "Belt Rock" from the Belt Supergroup. The sedimentary rocks in this group formed between 1.47 and 1.4 billion years ago in the Belt Basin. The roughly circular basin collected sediments from surrounding areas for millions of years. The basin was eventually buried and later re-exposed through the collision of several tectonic plates around 80 million years ago. Much of the Belt Rock found in the Mission Mountains is a crumbly sedimentary rock known as mudstone. The mudstone in the Belt supergroup is often characterized by mudcracks, which points to it being formed while wet, drying, cracking, and then being repeatedly flooded with new wet material that also dried and cracked. Most of the rock in the Mission Mountains hails from the end of the Proterozoic Eon, towards the end of what is called Precambrian time. Because they are so old, the only evidence of life in the rocks is algae blooms and very basic plant fossils. These organisms played, however, the important role of converting carbon dioxide in the water into oxygen that was pumped into the acidic and poorly oxygenated atmosphere. The color of the mudstone in the Missions has much to do with the presence of the mineral hematite during its formation. Hematite is formed by iron particles' reaction to oxygen in the atmosphere. Green and gray stones found in the Missions were most likely formed in deep water, the red in more shallow water. Ripple marks can be found in much of the rock; they would have formed mostly in shallow water with gentle waves. Uplift The features of the Mission Mountains strongly reflect work of the last few ice ages, the latest of those being just over 10,000 years ago. But the range is