1. Strip mine near Colstrip
2. Squall Line Sweeps Through Montana
3. Watershed of the Yellowstone River
4. *Triple Divide Peak in Glacier National Park
5. Oceanfront Property in Montana
6. *Mazama Ash Near Helena
7. Honey Car in Butte
8. *Chalk Cliffs in Central Montana
9. A Meteor Among Circumpolar Stars
10. *Recessional Moraines Near Turner
11. *The Cliffs of Crown Butte
12. *Ice Age Changes Path of the Missouri River
13. East Helena Superfund Site
14. Precipitation Map of Montana
15. *Madison Canyon Landslide
16. Lateral Moraine North of Missoula
17. White Cliffs of the Missouri
18. *Temperature Inversion in the Helena Valley
19. Why the Days Are So Short in December?
20. *Stromatolites Near Continental Divide
21. Sludge Injector Truck Fertilizes Fields
22. Mines in Little Rockies Are Visible From Space
23. *Jet Stream Delivers Balloon Bombs During WWII
24. How Glaciers Helped Form Flathead Lake
25. Igneous Dome in North-Central Montana
26. *Huge Iron Concretions in front of the Metra
27. Milltown Dam Removal
28. Montana Wind Energy Resources
29. Meltdown in Glacier Park
30. *An Oxbow Lake on the Hi-Line
31. The Berkeley Pit in Butte
32. A Septic Tank Near Montana City
33. Shorelines of Glacial Lake Missoula
34. Pedestal Rock Along White Cliffs Area of Missouri River
35. Giant Springs: An Artesian Situation
36. The Oldest Rocks Are In Western Montana
37. Tillite Found Among Pile of Erratics in North-Central Montana
38. Smelter Site Became the Old Works Golf Course
39. Logan Pass on the Continental Divde in Glacier Park
40. Evidence of Volcanism and Glaciation Along the Hi-Line
41. Weather Balloon Launch from Great Falls
42. Pollen Provides Clues About Past Climates
43. Shape of Land to Blame for Livingston's Strong Winds
44. *Lead Bullets Poison Eagles
45. *1935 Earthquakes Destroy Helena High School
46. Coalbed Methane Controversy
47. Counterclockwise Flow Around a Mid-Latitude Low
48. D-Day Moon
49. Carpenter Kicks 53-Yard Field Goal
50. *Limestone Wall Surrounds Little Rockies
51. Layers of Sediment from Glacial Lake Great Falls
52. *The Northern Lights
53. Chief Mountain
54. Storm Drains Are Not For Waste Disposal
55. Can you name these Montana rivers?
56. The K/T Boundary Near Jordan
57. Death By Dust In Libby
58. *SNOTEL Sites Measure Snow In Remote Areas
59. Slag Piles In East Helena
60. Dinosaur Discoveries Near Choteau
61. What causes the Chinook winds?
62. Canyon Ferry Dam on the Missouri River
63. Satellite View of Montana at Night
64. Jupiter and some of its moons
65. Which town has the coldest winters?
66. Aerial View of A Fault Scarp Near Helena
67. Decision Point for Lewis and Clark
68. An Alluvial Fan Near Ennis
69. Floodwaters Surrounded Glasgow in 1952
70. Goatlick Provides Minerals For Goats in Glacier Park
71. Where To Find Igneous Rocks In Montana
72. Radar Image Shows Tornado South of Malta
73. The Principle of Crosscutting Relationships
74. *Glacial Striations on the Ft. Belknap Reservation
75. Marlin, the Meteorite Man in Malta, Montana
76. The Belt Meteor Crater
77. Glacial Trough South of Red Lodge
78. Mountains of Conglomerate in Southern Montana
79. *Evaporation to Blame for Downbursts
80. *Geysers in Billings? Rhinos in Nebraska?
81. *Fata Morgana (mirage) from the CDT
82. The Great Falls of the Missouri
83. Grasshopper Glacier North of Yellowstone Park
84. Saline Seep Ruins Farmland
85. High Pressure to Blame for Dry Month in Montana
86. Lime Kilns Provided Mortar for Construction of the Capitol
87. The Best-Preserved Dinosaur Fossil in the World
88. Montana Counties Were Fallout Hot Spots During Cold War
89. Through the Guts of an Ancient Volcano
90. Glacier Park's Key Bed
91. *Rock Flour Needed to Make Glacial Milk in Cracker Lake
92. *The Madison Limestone: Montana's Rock of Ages
93. Great slabs of rock in the Belt Supergroup
94. Where cement comes from
95. Shatter cones from an ancient asteroid impact
96. How is electricity generated in Montana?
97. Wind Generators in Central Montana
98. Chalk Buttes in south-eastern Montana
99. Lewis and Clark Pass on the Continental Divide
100. Drumlin Field Resembles Tadpoles
101. Kettle Lake near Plentywood
102. *Native Americans Preferred Quartzite for Boiling Stones
103. Radiocarbon Dating Provides Clues about Montana's First People
104. *Ice Caves of Montana
105. Ringing Rocks of Montana
106. Smith Mine Disaster in 1943
107. *Ancient Ash in the Missouri Breaks of Central Montana
108. *Ancient Waterfalls Associated With Glacial Lake Great Falls
109. Tornado Wipes Out Ranch, Kills Two
110. Salinity of Surface Water in Earth's Oceans
111. Paleoecology Lab at Montana State University
112. Lone Peak Rock Glacier at Big Sky Ski Area
113. Fire, Floods Trigger Mass Wasting in Gates of the Mountains
114. *Hail Damage Path Visible from Space
115. *Snake Butte, A Hi-Line Landmark
116. *Microburst Flattens Trees North of Butte
117. Dike Cuts Through Eagle Sandstone
118. *Thin-Skinned Thrust Faulting Along the Rocky Mountain Front
119. Bakken Oil Field Visible from Space
120. Helena's Troubled Watershed
121. Gneiss in the Spanish Peaks
122. *Shonkin Sag Laccoltith
123. *Grinnell Glacier Moraine
124. *Scapegoat Mountain
125. Bighorn Canyon in Southeastern Montana
126. *Chinook Arch over Helena
127. *Marble Formed by Contact Metamorphism
128. Strange Flow of Rocks - A Rock Glacier beneath Mt. Powell
129. Fascinating Geology of Ear Mountain
130.*Kelvin-Helmholtz Clouds Over Helena
131. *Huge Pile of Erratics in North-Central Montana
132. *Special Conditions Needed for Rime to form
133. *Winter Count Recorded The Great Meteor Storm of 1833
134. The Big Flat sits on Flaxville Formation
135. *The St. Mary Canal System Feeds the Milk River
136. *The Snake Butte Boulder Train
More Pictures will be added from time to time.
Saturday, December 13, 2025
Montana's Earth Science Pictures (MESPOWs)
#8 - Chalk Cliffs in Central Montana (30-second video)
The Chalk Cliffs (above), located 25 miles north of Stanford are not chalk, but rather an especially light-colored sandstone. On the other hand, chalk is a soft type of limestone that forms from the accumulation of microscopic marine organisms, such as foraminifera and coccolithophores, which have shells made of calcium carbonate (calcite). When these organisms die, their shells sink to the seafloor, piling up to form a soft, white ooze. Over millions of years, the layers of ooze are compacted and lithified under pressure, hardening into chalk. The White Cliffs of Dover (England) are a famous outcrop of chalk.
Some beach . . .
In contrast, sandstones are composed of tiny rock fragments, primarily quartz, mixed with fragments of other minerals like feldspar, etc. The grains are typically glued together by natural cements such as silica (quartz), calcite, or iron oxide. The color and characteristics vary greatly, depending on the type of grains and cementing material, with iron oxides often creating red, yellow, or brown hues. Sandstones form in a variety of environments, including beaches, rivers, lakes, and deserts. The Chalk (NOT) Cliffs shown above are made of sand eroded from ancient mountains then deposited along the shore of an ancient sea, whereas many of the iconic sandstones in the soutwestern USA tell of ancient deserts.
The Virgelle sandstone . . .
The sandstone cliffs shown above are composed of a colorless quartz sand that was deposited near the shore of the Western Interior Seaway during the late Cretaceous period, which ended 66 million years ago. Cross-bedding suggests the sand was transported by coastal streams draining eastward as the seaway retreated. The cliffs are made of Virgelle sandstone - technically it's the Virgelle member of the Eagle formation. It is named "Virgelle" because the distinct sandstone was first identified near the tiny town of Virgelle, located along the Missouri River near Big Sandy (several miles west of Highway 87). An even more impressive outcrop of the Virgelle can be found along the White Cliffs of the Missouri, from Coal Banks (near Virgelle) to Judith Landing - a great canoe trip! The Virgelle is a "lower" member of the Eagle formaton, which means the Virgelle layers are near the bottom (older, deposited before other layers in the Eagle formation). The Virgelle varies in thickness but generally ranges from around 100 to 125 feet, reaching over 200 feet in certain areas. The Eagle formation outcrops in many places in central and eastern Montana - The Rimrocks of Billings are Eagle sandstone.
Right: Sketch borrowed from Roadside Geology of Montana, showing the location of the Virgelle Sandstone beach adjacent to the Western Interior Seaway during Cretaceous time. - Hyndman and Thomas, 2020
Stratigraphy . . .
In this part Montana the Virgelle and a transitional layer below it (Telegraph Creek Formation) were deposited on top of sea floor mud that became the Marias River Shale. The sediment of the Marias is composed of finer grain sediments deposited when the sea was deeper here (farther from the shore). Another shale, the Claggett, sits on top of the Virgelle, indicating the area went from being beneath deeper water (Marias shale) to being near the shoreline (Virgelle sandstone), and then back to a deeper environment (Clagget shale). The Western Interior Seaway was a shallow sea whose shoreline was everchanging. CLICK HERE to watch a video of the fluctuating Western Interior Seaway.
Term: stratigraphy
CLICK HERE to see my photo album from a hike onto the Chalk Cliffs (includes several drone photos).
Below: Google Earth view of the Chalk Cliffs - The "X" marks the area I explored.
Below: Here is how the Eagle formation (including the Virgelle member) is described on the MBMG Geology Map of Montana.
Friday, December 12, 2025
#1 - Strip Mine Near Colstrip, MT
This photo shows a coal "strip mine" located near Colstrip, 90 miles east of Billings. Known as the Powder River Basin, this region contains thick seams of coal that formed as coastal swamps were buried by sediments millions of years ago. Strip mining can be used in this area because the coal seams are closer to the surface than seams located in the eastern United States where underground coal mines are more common. Strip mining is much safer because miners do not have to go underground where collapses, gas explosions, and lung diseases are risks.
The majority of coal mined in the U.S. is from seams varying in thickness from 3 to 10 feet, although the seams in the Powder River Basin of southeastern Montana and northeastern Wyoming average 40 feet in thickness. Mining of this region's low-sulfur coal increased drastically in the early 1970s when the Clean air Act mandated that industries decrease emissions of sulfur dioxide, a gas that contributes to acid rain. The graph on the right shows how much coal was mined in Montana during the 1900's. The increase in the 1970's centered around the town of Colstrip - and in Wyoming, the town of Gillette became the hub of coal mining activity. Although Montana has more coal than any other state, Wyoming leads the way in the amount of coal mined. One reason for this is that Montana has a significant tax on coal sales, called the "Coal Severance Tax." Money collected from this tax is saved in a state "trust fund" for future generations.
What is it used for?
Montana's coal is primarily used for electricity generation. Some is burned at coal-fired power plants in Colstrip, with most mined coal (around 75%) shipped by rail to large, coal-fired power plants in the Midwest and Western states (like WA, OR), or exported internationally to countries like Japan, South Korea, and China for electricity generation. If you live in southern or western Montana, you've probably seen long trains loaded with coal on their way to these places.
Fossil fuels.
Coal, along with petroleum (oil), and natural gas are called "fossil fuels." Oil is used to make liquid fuels for trains, planes, and automobiles, and much of the natural gas is piped into homes where it is burned to heat air and water in furnaces and water heaters. Coal is not our only source of electricity, but coal-fired generators like those at Colstrip provide much of the electricity used in Montana. Hydroelectric dams provide the next biggest portion for Montanans. Nuclear plants (none in Montana) and wind generators are two other sources of electricity in the USA. Fossil fuels have been a focal point in the debate over climate change because carbon dioxide is emitted into the air as fossil fuels are burned. According to the "greenhouse theory" this carbon dioxide traps heat in our atmosphere, warming the world.
One Strip at a Time.
In the photo at the top of this page overburden has been removed, exposing a seam (layer of coal) that is ready to be mined. The long pile of rock (spoils) to the right is material recently removed from the strip of coal. The spoils sit atop the seam that was mined before the strip shown in the photo was exposed. After the exposed strip of coal is removed, the area to the left will become the next "strip". Its topsoil has already been taken away and stored. Next the coal will be removed and then eventually the broken up rock will be put back, smoothed out, the topsoil will be replaced, and the area will be seeded with native plants.
Term: overburden
Can you figure it out?
The diagram below is a cross-section of an area very similar to the area shown in the photo. Try to figure out which of the lettered areas on the diagram correspond to the following: coal, solid sedimentary rock layers, spoils, undisturbed topsoil, subsoil that has been returned, broken up rock that has been re-shaped, topsoil ready to be replanted, undisturbed subsoil.
#59 - Slag Pile in East Helena
If you've traveled through East Helena, you probably noticed the huge pile of black material at the ASARCO Smelter along the highway. The material, called "slag", is waste product produced as ASARCO removed lead from the ore.
Getting the lead out . . .
For more than a century, crushed ores containing galena (PbS) were brought to East Helena from as far away as Chile and Korea. Once at the smelter, the ores were "roasted" in order to remove the sulfur. The sulfur combined with oxygen to form a gas called sulfur dioxide, a pollutant that contributes to acid rain. A law called the Clean Air Act, which went into effect in the early 1970s, required that industries like the smelter remove this emission. A pollution-control device called a "scrubber" had to be installed to do this.
A density thing . . .
The roasting formed a material called "sinter," which was a mixture of lead oxide (PbO) and other rock materials. Next the sinter had to be melted. Crushed limestone and quartz were added to make it easier to melt the mixture. Once the material was melted, the heaviest stuff (lead) would sink to the bottom of the tank. The molten lead was then drained out through openings in the bottom into molds where it solidified.
Separation by melting . . .
This separation by melting is called smelting. The rest of the molten material, which had been floating above the layer of lead, also solidified, forming the black waste product called slag. For years the slag was disposed of by dumping it along the edge of the smelter property.
Other metals too . . .
Until its closure in the spring of 2001, the ASARCO Smelter shipped 10-ton pieces of lead by rail to a refinery back east. The refinery was able to separate trace amounts of other valuable metals such as gold and silver. In a typical year (early 1990s) the smelter's bullion yielded the following:69,000 tons of lead, 3,500 tons of copper, 690 tons of arsenic, 150 tons of bismuth, 20,000,000 oz. of silver, 200,000 oz. of gold
Anaconda's slag . . .
The smelter in Anaconda was designed to extract copper from the ores mined in Butte. The texture of Anaconda's slag is much different than the slag in East Helena. East Helena's slag is very "blocky," with pieces varying from fist-size to much larger. In Anaconda the slag is more like sand because the molten slag was spilled into water, causing it to harden and shatter into sand-sized pieces. In fact Anaconda's slag has been used in sand traps at the famous Old Works Golf Course.
To find out what might be in store for the future of the slag and the smelter site CLICK HERE (includes an article and short video from 9/23/25).
Term: smelting
Trivia . . .
Country Music Hall of Fame singer, Charlie Pride, once worked at East Helena's smelter and starred on the Smelterite baseball team.
Below: An older photo of the ASARCO Smelter site. The stacks were toppled several years ago, but the slag remains.
#81 - Fata Morgana from the CDT
Several years ago a friend and I did a snowshoe hike from Stemple Pass to Flesher Pass (near Helena) on the Continental Divide Trail (CDT). The temperature was pleasant, the snow was perfect, and it was sunny with no wind - but the best part of the hike was witnessing an unusual atmospheric phenomena known as Fata Morgana.
It's a trap! . . .
“Fata Morgana” is so-named because it is the Italian name for the Arthurian sorceress Morgan le Fay, and it was believed that she created these illusions of distant castles or land to lure sailors to their deaths. In reality all mirages are due to refraction (bending, redirecting) of light from distant objects. What we observed during the hike was the result of light from distant mountains being refracted as it traveled through layers of air that had different temperatures. The temperature inversion that blanketed the area that week was the major factor that allowed the sorceress to do her handiwork.
Inversion? . . .
During winter months, the mountain valleys of western Montana are prone to inversions. They're called inversions because they are upside-down situations. The temperature of the atmosphere NORMALLY gets colder as you get farther away from the surface. However during inversions, air near the surface is colder than the air above. Inversions tend to form during stretches of clear, calm, very cold weather. Without clouds, heat given off by the earth escapes easily into space, causing a layer of cold air to develop at the surface. An especially strong inversion was present in the Helena-Lincoln area when the Fata Morgana photos were taken - There was a layer of very cold air in the valleys with warmer air above.
Illusionary beauty . . .
Fata Morgana is a type of mirage known as a superior mirage. All mirages are caused by the refraction (curving or redirecting) of light as it passes through layers of air with different temperatures and densities, creating false images, like seeing "water" on a hot road or distant objects appearing to float. This happens because hot air (less dense) and cool air (denser) refract light differently, making the brain perceive bent light as if it traveled in a straight line from a different location (diagram). This bending or redirecting occurs because light travels at slightly different speeds when passing through different mediums. When there are stark changes in air density due to layers of air having different temperatures, this can create the illusion of distant objects or water. For instance, on a hot day, the air near on a paved highway is much warmer and less dense than the air above it, causing light rays to bend upwards, which creates the illusion of water on a road’s surface - this is an inferior mirage. The intricate nature of Fata Morgana involves multiple curved light rays converging towards the observer's eye. This convergence creates an illusionary effect, making objects appear inverted or smeared upwards into towering cliffs as shown in the photo atop this page.
Term: refraction
CLICK HERE to learn more about Fata Morgana (Wikipedia)
CLICK HERE to access my blog and photo tour of the hike we were doing when we witnessed the Fata Morgana.
CLICK HERE to watch a short YouTube video that demonstrates refraction.
Below: The situation we witnessed was more complicated than the one illustrated below, but the diagram may help you understand how refraction is involved.
Below: These two photos taken from the same vantage point show a mirage effect with Three Buttes on the Ft. Belknap Reservation.
Thursday, December 11, 2025
#7 - When you gotta go, you gotta go!
How sweet it is . . .
The photo shows one of the "honey cars" that served as toilets for the men as they worked the mines deep beneath the surface of Butte. These "sweet" smelling rail cars consisted of iron tanks with toilet seats on top. The rail car design allowed the honey cars to be moved in and out of the mines on the same system of rails that was used to haul copper ore to the surface.
Hazards of working the underground mines . . .
The work of the underground miners was both demanding and dangerous. Occasionally parts of the mine would collapse, burying men beneath large pieces of rock referred to as "Dugans" (named after the family that owned the local mortuary). Fire was also a danger. In 1917 an underground fire 2,400 feet below the surface in the Granite Mountain Mine* killed 168 men. For those who survived careers underground, years of inhaling the dusty air often caused lung diseases that stole years away from retired miners.
Electrifying the USA . . .
The underground mines of Butte dominated world copper production between 1887 and 1920. By 1916 over 14,000 miners worked the underground mines on rotating shifts around the clock. At one point about a forth of the world's copper was coming out of Butte. As result, Butte is sometimes called "the city that electrified a nation" because Butte copper was used as wiring in homes. The light bulb had been recently evented and people all over the country wanted the new technology. By 1950, over 400 underground mines, consisting of several thousand miles of interconnected workings, had operated or were operating. The last underground mine closed in 1981.
NOTE: The photo was taken at the World Museum of Mining which is located near the campus of Montana Tech in Butte.
Terms: ore, open pit mine
#12 - Ice Age Changes Path of the Missouri River
Doesn't make sense . . .
The Milk River starts in Glacier Park, flows up into Canada and then returns to Montana northwest of Havre. Its valley is small, as you would expect for such a small river. However, a few miles east of Havre the valley of the Milk River suddenly becomes very wide, which is very unusual! From there to where it empties into the Missouri near Glasgow, the little river meanders along in the spacious floor of a broad valley that it could not have eroded. There is no corresponding change in resistance of the bedrock, so their had to be some explanation for the discrepancy.
A Hand-Me-Down Valley . . .
Shortly after the turn of the century geologists pointed out that the broad valley of the Milk River from Havre to Glasgow is about the size of the Missouri River valley below (east of) Ft. Peck, and that the Missouri River flows through a narrow canyon for a long distance between Ft. Benton and Ft. Peck. They suspected that the Missouri River may have occupied the broad valley along the Hi-Line until the ice pushed it south during a recent ice age, and then after the ice age the Milk River found that old pre-ice age valley of the Missouri River.
Missing link found . . .
More evidence was found, supporting the hypothesis. Another oversized valley, the valley of Big Sandy Creek south of Havre, was studied and determined to be a portion of the ancient valley that connected the current Missouri to its old valley on the Hi-Line. The ancient valley was not obvious at first because it was hidden beneath gravels brought to the area by the continental glacier and then transported again by meltwater as the ice age ended. More field work revealed the final connecting segment of the abandoned Missouri valley near Havre, which was also buried beneath glacial sediments. Mystery solved!
Term: stream channel