#1 - Strip Mine Near Colstrip, MT

Photo credit: Los Angeles Times, click on it to enlarge. No need to go underground
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 1970's brought changes.
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

Photo courtesy of the Montana Environmental Trust Group; click on it to enlarge An eyesore . . .
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

Above and below: Both photos were taken from the Continental Divide Trail west of Helena. The top one shows the mirage affect known as Fata Morgana, and the bottom one is for comparison.

A real treat! . . .
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 is that we were able to witness 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 readers understand how refraction is involved.

#7 - When you gotta go, you gotta go!

If you mention "Butte mining" to a young Montanan, chances are their first thoughts will be of the Berkeley Pit. However, open-pit mining in Butte didn't start until the mid-1950s. This week's picture is a symbol of the earlier years of underground mining; those years when Butte earned its title as "the Richest Hill on Earth."

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

Map courtesy of Mountain Press Publishing of Missoula, Montana; click on map to enlarge.

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

#11 - The Cliffs of Crown Butte

Click on photo to enlarge.

Volcanic past . . .
The photo above shows the cliffs of Crown Butte a flat-topped butte located 20 miles west of Great Falls. Both Crown Butte and its larger neighbor, Square Butte, are formations called laccoliths. Laccoliths are formed when magma is injected between layers of sedimentary rock beneath the surface. The magma, which came from an ancient volcano centered 10 miles south of Cascade, worked its way through cracks in the bedrock to get here. Eventually the magma hardened, forming a very durable type of rock that has survived millions of years of erosion. In the meantime the softer sedimentary rocks (sandstones, etc.) that once covered the laccolith have been eroded away, exposing the laccoliths as buttes that can be seen throughout central Montana.

Layered igneous complex . . .
Although layers are usually associated with sedimentary rock, the igneous rock of the butte is made up of very distinct layers. Evidently, the magma filled the laccolith in "pulses" with each new pulse forming another layer. Closer examination reveals a thin lighter-colored layer between each of the thicker, darker layers. This separation within each pulse may have happened as a result of differences in the densities and/or freezing points of various minerals in the magma. Another theory is that the thin light-colored layers formed as a result of water soaking in from the sandstone above before the next layer of magma was injected.

Publc access . . .
The Nature Conservancy purchased Crown Butte in order to preserve the natural grassland ecosystem located on top of the butte. Except for an occasional hiker, the ecosystem sits undisturbed about 1,000 feet above the surrounding prairie. CLICK HERE to access my blog and photo tour - Crown Butte is one of my favorite places!

Terms: laccolith, intrusive formation

#2 - Classic Squall Line of July 8, 2002

Radar can "see" the storm . . .
This radar image shows a squall line that swept through central and eastern portion of Montana on the evening of July 8, 2002. Blue areas indicate light precipitation, green areas indicate moderate precipitation, and the red areas show where precipitation is intense. The image was captured by the National Weather Service's Radar device located in Glasgow. The N.W.S. has radar in Glasgow, Great Falls, Billings, and Missoula. These cities were selected because they are far enough from each other to give the N.W.S. good coverage of the entire state.

Somewhat unusual in these parts . . .
A "squall line" is a line of thunderstorms that forms along a cold front as cooler air pushes into very humid, warmer air. Since air in the Midwest and southeastern United States tends to be more humid than in Montana, squall lines are much more common in these regions.

Rising humid air is the key . . .
Where cooler air is pushing into warmer air along a cold front, the warmer air rises because it is lighter. As this warmer air is forced upward, it cools by expansion. Eventually the cooling causes the vapor (humidity) in the rising air to condense, forming cloud droplets or ice crystals. The changing of vapor to liquid or solid releases heat which helps the air continue to rise, and the cycle continues.

It just kept going . . .
If the warmer air is especially humid as it was on July 8, a line of dangerous thunderstorms may sweep through an area. Since this cold front moved eastward, this squall line also moved eastward, causing lightning, hail, strong winds and even a threat of tornadoes across much of Montana.

Term: cold front

Below: This is a G.O.E.S. East Satellite view of the squall line at 5 pm MDT on July 8, 2002 - The same storm shown on the radar image above. The line of thunderstorms extends from southwest Saskatchewan toward northcentral Wyoming.