#58 - SNOTEL sites save many trips to high, cold places.

Map courtesy of Natural Resources and Conservation Service

The dots on this map mark the locations of automated stations that measure how much snow has fallen. The system, called SNOTEL (for SNOwpack TELemetry) is operated by the Natural Resource and Conservation Service. SNOTEL instruments help scientists to know how much snow sits in these remote mountainous locations, so that they don't have to visit the areas to make measurements.

Interactive SNOTEL Map of Montana

Right: I took this photo of my friend Mark at a SNOTEL site near Lincoln, Montana.

Important predictions . . .
The data obtained from the sites helps determine how much spring runoff to expect as the snow begins to melt. This is especially important in the management of reservoirs along Montana's rivers. For instance in April of 1996 Canyon Ferry Reservoir was lowered by over 15 feet because SNOTEL data indicated that there were unusually high amounts of snow present in the Upper Missouri Basin. Water from the reservoir was let through the dam in order to make room for the runoff that would certainly drain into Canyon Ferry as the snow began to melt rapidly in May and June.

A pillow sensitive to pressure . . .
Although SNOTEL sites have several types of weather instruments, the most interesting is the "snow pillow" (see picture below). The pillow is made of various materials including steel, rubber, and a material called hypalon. It is filled with a solution of antifreeze (50/50 mix of water and ethanol). As snow accumulates on the pillow, it increases the pressure within the pillow. A fluid line runs from the pillow to the shelter where an electronic device determines and records the snow's water equivalent. Periodically radio waves transmit this and other data to climatologists.

Unique to the West . . .
The SNOTEL system is the biggest provider of real-time snowpack and high elevation climatic data in the world. It is only used in the western part of the U.S.A. where there are about 650 sites - Montana has 90.

Terms: telemetry, reservoir

#60 - The Famous Egg Mountain Fossil Site near Choteau, Montana

Diagram courtesy of Montana Geologic Road sign program. A revolutionary discovery . . .
There have been some extraordinary dinosaur discoveries in our state over the past several decades, but the discovery that put Montana on the dinosaur map were found near Choteau in 1977 by Marion Brandvold, owner of the Trex Agate Shop (aka "The Rock Shop") in Bynum, Montana. The following year she showed the bones to paleontologist Jack Horner, and the rest is history. Horner and the late Bob Makela dug up the first nest of baby dinosaurs ever found. Over the next several years Horner and his team team discovered was 14 dinosaur nests in a single area of the site, providing the first strong proof that dinosaurs fed and cared for their young and exhibited complex social behaviors.

Good mothers . . .
The size of the shells indicated that the babies were about 12 inches long at birth, but bones of much larger infants were also discovered in some of the nests. This suggests that these dinosaurs cared for their young, unlike modern sea turtles that lay their eggs in the sand and leave the babies to fend for themselves. Furthermore, the teeth of the infants showed signs of wear, suggesting that the adults brought food to the nests. As a result, the newly discovered species (a type of duckbilled dinosaur) was named Maiasaura peeblesorum - Maiasaura is Greek for "good mother lizard", and Peebles honors the families of John and James Peebles, on whose land the finds were made.

Social colonies, nesting grounds . . .
Many of the nests were found at two locations called "Egg Mountain" and "Egg Island". These were small islands when the eggs were laid, yet the dinosaurs kept their nests separated by 23 feet, the approximate length of an adult Maiasaur. This suggests a type of cooperation typical of animals that live in groups. Nests at these two sites were found at three different levels, separated by layers of sandstone. Apparently the islands were nesting grounds that the Maiasaurs returned to year after year.

Term: paleontology

For a more detailed article about Egg Mountain, CLICK HERE.

Below: Illustration of a herd of Maiasaura walking along a creekbed, as found in the semi-arid Two Medicine Formation fossil bed. This region was characterized by volcanic ash layers and conifer, fern and horsetail vegetation. (Wikipedia)

#61 - Montana's Chinook Zone

Above: The area outlined in white is where Chinook winds are most common in Montana.

Strange winter warmth . . .
In Great Falls on January 11, 1980 the temperature rose from -32 F to 15 F in 15 minutes. During the night of January 14-15, 1972 an official weather observer in Loma (shown on map above) recorded a 103 degree change within 24 hours! The mercury went from -54 F to 49 F as calm arctic air was replaced by winds from the west blowing 30-40 mph. In both cases the dramatic warming was due to a weather phenomenon known as a Chinook Wind.

These unusually warm, winter winds happen at mid-latitude locations throughout the world and they are known by other names. In the west and northwest USA they are called Chinooks, and they can happen at any location that has high mountains to the west, such as the Helena Valley (15 miles east of the Continental Divide). They are most common along the eastern slopes of the Rockies from northern New Mexico all the way up through Alberta (Canada). The area of Montana outlined by the white line (see map above) is one place where Chinooks are especially common, and sometimes extreme.

Recipe for a Chinook . . .
In order for these warm winds to happen, three things are needed:

1. For one, a strong westerly (or southwesterly) flow of air is needed. West to east is the prevailing wind direction in Montana. However, if there is going to be a dramatic Chinook effect, the winds need to be especially strong.

2. Moist air from the Pacific is another key ingredient. This air contains an abundance of water vapor (humidity) that entered the air as water evaporated from the ocean. In order to make the change from liquid to vapor these water molecules had to absorb heat from their surroundings. So, especially moist air also contains lots of energy, referred to as "latent heat".

3. The final ingredient is mountains. Since the Rockies are somewhat narrower and higher in the area of Glacier Park and the Bob Marshall Wilderness, Chinook winds are especially frequent in the zone shown within the yellow line on the map.

Cloud formation releases the latent heat . . .
As the moist Pacific air blows into the mountains of Glacier Park, the mountains force the air to rise, causing the air to cool by expansion. As a result the vapor changes into ice crystals that grow and then fall as snow on the west slopes of the mountains. The key to the Chinook effect is that when the molecules of water vapor freeze, they release heat to their surroundings. This is the same latent heat that was absorbed as the molecules evaporated from the ocean. It is this heat that is released as clouds form on the west slopes that makes the Chinook winds so warm. As this air flows down the east side of the park into Browning, it will also be warmed by compression . . . But this warming by compression happens whether or not there is a Chinook wind. To view a short video about latent heat, CLICK HERE.

Below: The top diagram illustrates a situation in which air that is completely dry moves into Montana. Although air without even a trace of vapor is not realistic, the diagram shows the temperature changes associated with rising (expanding) and sinking (compressing) air. The bottom diagram shows the role that moisture-laden air plays in the development of Chinooks. With the heat released by water molecules as they become ice crystals, the temperature of the air as it reaches the peak is not nearly as cold. Then the air is compressed as it flows down slope toward Browning, reaching Chinook-like temperatures. NOTE: The diagram is highly simplified. The mountains between Washington and Montana are much more complex and the elevation of Browning is actually quite a bit higher than that of locations in Central Washington.

Term: latent heat

#62 - Canyon Ferry Dam on the Missouri River

This photo shows Canyon Ferry Dam and Reservoir, 13 miles northeast of Helena. The dam was built by the Bureau of Reclamation on the Missouri River between 1949 and 1954 . Like other dams in Montana, Canyon Ferry serves several purposes, including power generation, flood control, recreation, and irrigation.

Your dam wind . . .
One interesting aspect of the dam is a daily wind situation that exists here in the summer. According to a colleague of mine who used to do a lot of wind surfing, a significant wind develops by the middle of sunny summer days in the area between the dam and Cemetery Island. The wind, which blows from the dam to the island, is most likely caused by the fact that land heats up faster than water. As the morning sun shines on the area, the island warms up faster than the surrounding water. By mid-day this hotter air above the island begins to rise. This convection causes an area of low pressure to form over the island. A fairly strong wind begins to blow from the dam as cooler air from below the dam moves to replace air rising from the island.

The big pipe . . .
Canyon Ferry Reservoir provides water used to irrigate farmland in the Helena Valley and also provides some water for municipal use in the city of Helena. Water enters the large pipe shown in the photo. A closer view of the pipe is shown in the photo below. A pump pushes the water up through the pipe, which runs underground to a storage reservoir 7 miles west of the dam. From there a system of canals deliver the water to various parts of the valley for irrigation.

Electricity . . .
Water flows through openings in the dam, drops through large tubes called "penstocks", and turns fan-like devices called turbines. These turbines move huge magnets located near wires, causing electricity to be generated in the wires. The device designed to convert the motion into electricity is called a generator.

Term: convection

#63 - Satellite View of Montana at Night

Last one out of town shut the lights off!
This enhanced satellite view shows the distribution of nighttime lights across Montana. Can you identify the seven cities that have AA high schools (Billings, Bozeman, Butte, Missoula, Kalispell, Helena, Great Falls)? Perhaps you can pick out several smaller communities as well. CLICK HERE to see a recent image of the USA at Night.

Darkness can be a good thing.
The image was provided by the International Dark-Sky Association. The IDA is an organization dedicated to building an awareness light pollution and helping people understand the importance of investing in certain types of lights for outdoor lighting. One reason that the IDA works to promote nighttime darkness is that darker skies make it much easier to view celestial bodies. Even in a state as sparsely populated as Montana both the quantity and quality of what can be seen in the nighttime sky depends on where you are. For instance, someone in Billings will not be able to view auroras or stars nearly as well as someone in Jordan (J). The IDA strives to preserve dark skies in order to enhance viewing of the nighttime sky for everyone, and it believes that one key is for cities like Billings to select types of outdoor lights that minimize light pollution.

Centers.
Although Lewistown (L) is the geographic center of the state, Helena (H) seems fairly well-centered among Montana's larger cities. The "middle of nowhere" distinction would have to go to Jordan (J), a speck of light in the center of eastern Montana surrounded by miles of darkness.

Urban Sprawl.
Notice the area extending south from Missoula (M). This line of lights marks the location of the Bitterroot Valley. Lolo, Florence, Victor, Stevensville, Corvallis, Hamilton, and Darby are all located in this rapidly growing valley.

Term: urban sprawl

#64 - Jupiter's Four Large Moons

Grab your binoculars. . .
Many of those bright points of light that we call "stars" are not stars at all. Some are planets, many are distant galaxies, and others are clouds of gas and dust called nebulae (plural for nebula). Although you can't always see them, Venus, Mars, and Jupiter (planets - NOT stars) are three of the brightest objects in the night sky - However, they aren't always in the right place for us to see them. When this picture was posted in March of 2004, it was an especially good time to see Jupiter. To find out what planets are currently visible in the night sky, CLICK HERE. IF in fact Jupiter is visible, check it out with a good pair of binoculars - You should be able to see some of its four large moons. Jupiter had 95 officially recognized moons as of March 2025, but the first four (the big ones) were discovered by Galileo in 1610. They are named Io, Europa, Ganymede, and Callisto.

Jupiter at its best . . .
The best time to see Jupiter is when it is at opposition. This happens when it is on the side of the Earth opposite the Sun. When it is opposite the Sun, Jupiter is visible all night, rising in the east in the evening and setting in the west around sunrise the next morning. On the other hand, when the Earth and Jupiter are on different sides of the Sun, Jupiter cannot be seen for months.

To find our where the planets are in relationship to the Sun (and each other), CLICK HERE, set the "size" at 1000, and then select "update".

Galileo rocked the boat . . .
Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted a telescope and began to look at the heavens. His discovery of the moons, along with other discoveries, revolutionized astronomy and challenged some of the religious and philosophical views of the time. Galileo's report that Jupiter is orbited by moons contradicted the geocentric theory, which held that the Earth was the only center of motion in the universe. With his telescope, Galileo also found that Venus went through phases like our Moon; a phenomenon that could not be explained in terms of an Earth-centered system. Furthermore, his discovery of sunspots showed that it had "blemishes," countering the Aristotelian view that the Sun was perfect. In his old age Galileo was forced by The Inquisition to recant his belief in the Copernican (heliocentric) Theory that the planets orbit around the Sun.

Term: The Inquisition, heretic

#65 - Which town has the coldest winters?

A dubious distinction . . .
The map shows the location of four small towns known for their especially cold winter temperatures. Quite often the nightly news reports that one of these towns has recorded the coldest temperature in the state during the previous 24 hours. But which one earns the distinction of having the coldest winters?

Climate factors . . .
Climate is the "average weather" experienced at a location over a period of years. Of course there is much more to climate than just temperature. Humidity, the type and timing of precipitation, cloud cover, seasonal change, and wind are also important considerations. Each of these "symptoms" of climate is influenced by various combinations of the climate factors listed here.

latitude . . . . . . . . . . .elevation

prevailing winds . . . . . . .the shape of the land

nearby ocean currents . . . . distance from large bodies of water

Which climate factors? . . .
For the towns in question a few climate factors must be taken into consideration. Elevation is a huge influence when it comes to temperature. Towns located at higher altitudes tend to have colder temperatures than towns at lower elevations. Here are approximate the elevations of the towns in question (given in feet above sea level).

Wisdom: 6,100 ft. . . . Westby: 1,900 ft. . . . West Yellowstone: 7,000 ft. . . . Cooke City: 8,000 ft.

Another consideration is latitude. Obviously Westby is the farthest north of the four towns. A third consideration is prevailing winds. In Montana the wind usually blows from the west, southwest, or northwest. Since winds are names by the direction that they are coming from, our wind belt is known as the "westerlies".

And the winner is . . .
Despite the fact that it sits at a much lower elevation than the other three towns, over the past 30 years Westby has experienced the coldest winters in Montana. Although Cooke City edges out West Yellowstone as the coldest town based on year round temperatures, Westby's winter temperatures average about 5 degrees colder than the nearest competitor (see yellow lines on the graphs below).

The Canadians are coming . . .
Westby's distinction is due to a combination of latitude and prevailing winds. Since Westby is farthest north it gets less solar energy in the winter than the other towns. More importantly, its location in the northeastern corner of the state also means that Westby is the town most likely to experience air masses that move in from Canada (see map to right). As this cold air moves southward the westerlies often prevent it from reaching western and southern regions of the state.

Climate graphs (below) . . .
The yellow line on these climate graphs show that Westby has a greater annual temperature range than Cooke City. Locations that are closer to the center of continents tend to have hotter summers and colder winters than places that are closer to large bodies of water. Water warms more slowly than land during the summer and it also cools off more slowly than land during the winter. This is why Bismarck, North Dakota has hotter summers and colder winters than Seattle. Although the ocean is not a huge influence in Cooke City, it is more likely to influenced by air from the Pacific than Westby is. In the winter Maritime Polar air from the Pacific is cool and moist compared to the cold, dry Continental Polar air, and the bitter cold Continental Arctic air that often moves into northeastern Montana.

. Term: annual temperature range

#66 - Helena has its faults.

Photo courtesy of Mike Stickney, Montana Bureau of Mines and Geology

A torn surface . . .
This aerial photo shows the western edge of the Helena Valley just a few miles north of Helena. If you look closely you can see an elevation change in the surface along a line between (and parallel to) the railroad tracks and Green Meadow Drive. If you can’t tell where it is, scroll down to see the labeled photo near the bottom of this page. The linear feature, called the Iron Gulch fault scarp, is where the ground surface has dropped three to four meters above a “normal fault” as a result of earthquakes over the last 130,000 years. It is not known how many quakes it took to form the Iron Gulch scarp, but it could probably be determined by careful study if a trench were dug across the scarp.

One quake at a time . . .
Earthquakes happen when there is movement along a fault, however, not all movements cause scarps to form. For example, during the historic quakes that rocked Helena in 1935-1936 there were no surface ruptures. In contrast, a big earthquake near West Yellowstone in 1959 caused several new scarps, including one that was 14 miles long and as high as 21 feet. Like most fault scarps, the Iron Gulch scarp is not in solid rock, but rather in gravels and soil above the bedrock. The actual fault is located within bedrock, buried beneath soil and hundreds of feet of gravel.

Map courtesy of Montana Bureau of Mines and Geology . . .
The map at the right shows faults (dashed lines) that have been identified in the Helena area as well as post-1982 epicenters (yellow circles). The stars mark epicenters of post-1900 earthquakes with magnitudes of 5.5 or greater. Some geologists believe that the Iron Gulch fault (#683) extends to the southeast in the subsurface, all the way to East Helena. All of the faults shown on the map played a role in the formation of the valley. Like many basins in the northern Rockies, over millions of years, the block(s) of bedrock that the Helena Valley sits on has dropped down one earthquake at a time along these faults to form a basin surrounded by mountains (called a graben). Since its formation the Helena Valley has filled with gravels, sands, and silts washed down from the surrounding mountains. As Helenans learned during the 1935 quakes, structures built on these deep, loose sediments shake much more violently than structures built where bedrock is not far below the surface.

Terms: graben, normal fault

#67 - Decision Point for the Lewis & Clark Expedition

Click on image to enlarge. A fork in the river . . .
This aerial photo, shows the confluence of the Marias and Missouri Rivers 10 miles near Loma (between Great Falls and Havre). When the Lewis and Clark expedition reached this confluence on June 2, 1805 they faced a tough decision. The Mandan tribe, who they'd spent the winter with in North Dakota, made no mention of this "fork" in the river - so, the expedition was not sure which way to go. As one historian put it, they had reached the "where the hell are we" phase of their expedition. In the photo it seems obvious which branch is the main channel (the Missouri River). Perhaps in the spring of 1805 an usually high amount of runoff in the to the northeast of here (Marias Basin) made it difficult to distinguish the main channel from its tributary. Although they found the south fork to be wider (372 yards) compared to the north fork (200 yards), the muddy water in the north fork more closely resembled the river that they had been traveling on since leaving the Mandan village earlier that spring. On the basis of its muddy appearance, the men strongly believed the north fork to be the route that they should take.

Decision Point . . .
Lewis and Clark didn’t agree their men, but they realized the importance of choosing the right course. So, the expedition camped for nine days while they investigated the two rivers. The captains began the investigation by dispatching three men in canoes up each of the forks. While they were gone, Lewis climbed to what is now called Decision Point Overlook for a better view of the surrounding land. He believed that one channel traveled too much from the north to be the Missouri, and that its waters were not clear enough to be from the snow-capped peaks of the Rockies that he could see in the distance. When the canoes returned their findings proved inconclusive, so the captains set out to see for themselves. Clark went forty-five miles up the south fork, finding that it ran swift and true to the west of south. He returned, convinced that it was the Missouri. Lewis went nearly eighty miles up the north fork, confirming that it headed from too much to the north for their route to the Pacific. Their decision to follow the south fork was confirmed when they reached great waterfalls that the Mandans had told them about (near present-day Great Falls).

Tribute to a cousin . . .
Once Lewis determined that the north fork was not the Missouri he decided to name it Maria’s River in honor of his cousin, Miss Maria Wood. Over the years the apostrophe was dropped and the pronunciation changed to “ma-RI-us”. Terms: confluence, tributary

#68 - Cedar Creek Alluvial Fan

The Perfect Alluvial Fan . . .
The area shown on the map is located a 5 miles southeast of Ennis (30 miles northwest of Yellowstone Park). A photo of the area is shown at the bottom of this page. The map, which represents an area about 5 miles x 5 miles, was copied from an older USGS contour map. Such maps, often called topographic, or "topo" maps, use contour lines to show the shape of the land. Older ones also used shading to help the map-reader visualize the topography.

What's so special about this area?. . .
The significance of this map is that the contour lines reveal a distinct fan-shaped formation in the area where Cedar Creek flows out of the Madison Range. The formation, called the Cedar Creek Alluvial Fan, is one of the best examples of an alluvial fan in the world and is sometimes featured in geology textbooks.

How did it get there?. . .
Streams such as Cedar Creek transport a variety of rock materials, including clays, silts, sands and gravels. Where streams flow from steep slopes onto flatter areas they slow down, losing their ability to efficiently transport gravels and larger sands. The smaller pieces, including clays, silts, and some sands continue to go where the water takes them while the gravels begin to build up at the edge of the valley. Eventually so much gravel is deposited that the stream changes its course, and the process repeats itself over and over and the fan-shaped deposit takes form. That's exactly what has happened here. Since the last ice age ended about 10,000 years ago, Cedar Creek has carried gravels out of the mountains and deposited them on the edge of the valley, forming this classic alluvial fan.

Below: This Google Earth image of the Cedar Creek alluvial fan shows what the area would look like if your were approaching (flying) from the west. You can see Ennis Lake, the town of Ennis, and Cedar Creek cutting through the alluvial fan. Cedar Creek is a tributary of the Madison River which flows northward (right to left across the center of the image) into Ennis Lake. Soils have developed on top of the gravels, and grasses have taken root. Cedar Creek continues to wind its way over the fan.

Term: alluvium

#69 - Levees Protect Glasgow from Flooding

Photo by Paul Monson, courtesy of Cole’s Studio with thanks to Samar Fay of the Glasgow Courier.

This photo shows how levees protected Glasgow during a flood that occurred in April of 1952. The camera was pointed toward the southeast. Glasgow is located on the floodplain of the lower Milk River, about 15 miles northwest of where the Milk empties into the Missouri. Although flooding occurred as far west as Havre, less that a dozen people were injured and property damage was less than $7 million. As the photo shows, levees built around much of the town’s perimeter prevented it from being inundated. Levees are man-made embankments that protect towns or agricultural areas from flood damage.

Needed a solution . . .
The Glasgow area also flooded in 1899, 1906, 1912, 1917, 1923, and 1928.The city of Glasgow built the levees after the 1928 flood, and then heightened them and extended the project in 1938. During flooding in 1939 emergency responders reinforced the levee, which held back floodwaters caused by ice jams and snow melt. The city was nearly surrounded by floodwaters, but remained dry.

Weather helped out in 2004 but not 2011 . . .
During the early spring of 2004 there were concerns that the Glasgow area would have a flood similar to the 1952 event because record amounts of snow (67.7 inches) at Glasgow exceeded those of the winter of 1951-1952 by over 7 inches. Fortunately, nearly perfect temperature conditions during March caused the snow to melt slowly, allowing the area to avoid a flood similar to the one experienced in 1952. In contrast, record winter snowfall (ove 100 inches!) coupled with spring rains caused flooding in the Milk River Basin and along many rivers throughout Montana. Once again, Glasgow's levee system held.

Montana’s flood of the century . . .
The worst flood disaster in Montana’s history happened in June of 1964 along both sides of the Continental Divide in the northwestern part of the state. As much as 14 inches of rain fell in 36 hours, adding runoff to streams that were already swollen because of snowmelt. The result was 30 deaths and $55 million in damage, including the failure of two irrigations dams. One of the dams, located near Dupuyer (75 miles northwest of Great Falls) washed away, causing a flash flood that took 19 lives.

Terms: floodplain, levee, runoff

Below: A ground level view of part of Glasgow's levee system during the historic flood of 2011.

#70 - Goat Lick near Glacier Park

Located along U.S. Highway 2, near the southern tip of Glacier National Park, is an exposed riverbank where mountain goats and other animals come to lick the mineral-laden cliffs. From the parking area, a short paved path leads to an observation stand overlooking the waters of the Middle Fork of the Flathead River. Here, the river's current has cut deeply into the easily eroded soil, creating steep drop-offs and exposing a mass of light gray clay containing minerals craved by mountain goats and other animals. Four natural mineral licks are known in the park, but no other lick receives as much use as this one.

Spring awakens cravings . . .
The Goat Lick is a rocky exposure of comprised of gypsum, kieserite, and sulfates. The craving for sodium and the shift to green vegetations each spring, prompt the goats to visit the Goat Lick. Calcium, potassium, and magnesium found in the lick may help replace the elements goats lose from their bones during the winter. Additional explanations for visits to the lick include: an acquired taste for salts; a need for the minerals as a digestive acid; and the high goat concentrations, which may allow for more intensive social interactions.

Like a fine restaurant . . .
Glacier National Park goats travel as far as 4 miles to get to the Goat Lick, while others from more widely dispersed areas in the Flathead National Forest, travel several times that distance. April through August is the most concentrated use period, although use occurs year-round. During late June and July, dozens at a time gather here. A population of approximately 95-120 mountain goats from Glacier National Park, and 20-45 from the adjacent national forest, use the lick. Elk and deer are also attracted to these natural minerals. Young mountain goats learn the route from the older animals. Most of their travel occurs on established trails. One well-worn goat trail traverses the crest of Running Rabbit Mountain and down the slope to the Goat Lick. Source . . .
Glacier National Park. Goat Lick Overlook (brochure). National Park Service of the U.S. Department of Interior.

Term: social interactions

Below: The goat lick as seen from the viewing area along Highway #2.

#71 - Igneous Rocks of Montana

There are three basic categories of rocks - sedimentary, metamorphic, and igneous. The most common type of rock found at the surface in the eastern two-thirds of Montana is sedimentary (sandstones, shales, limestone, etc.). Western Montana has the best variety, with each type present in different areas. Igneous rock is formed when magma or lava cools. The red and gray areas on the map show where igneous rock can be found at the surface, or just beneath the soil. The red areas are where lava erupted onto the surface and hardened to form a category of igneous rock that geologists refer to as "extrusive" (a.k.a. volcanic). The gray areas are where the magma hardened beneath the surface, making a kind of igneous rock is called "intrusive" (a.k.a. plutonic). Basalt is the most common specific type of extrusive igneous rock and granite is the most common specific type of intrusive igneous rock.

Intrusive, or Extrusive - How can they tell? . . .
One thing that helps geologists determine whether an igneous rock is intrusive or extrusive is the size of the crystals, or grains, that makes up the rock. When lava erupts onto the surface it tends to cool quickly, whereas magma beneath the surface may take centuries, or even thousands of years to harden. As a result the various minerals in lava have little time to organize themselves into crystals. Consequently, extrusive rocks tend to be fine-grained and display a more uniform color than intrusive rocks. On the other hand, as magma cools slowly beneath the surface, minerals have more time to form crystals. The crystals eventually run out of space as they grow into each other, forming interlocking "grains" of various colors, such as the quartz (white), biotite (black), and feldspars (pink, gray) that can be seem in a typical granite.

No Volcanoes - Just Left-Overs . . .
As the map at the top of this page shows, many of the small mountain ranges in central Montana owe their existence to volcanic activity. Although some may resemble volcanic cones, they are not. Instead they are simply the eroded remains of cones and/or lava that poured onto the about 50 million years ago. Geologists refer to these areas as "volcanic fields, complexes, centers, or piles".

Terms: plutonic rock

#72 - Toto, we're not in Kansas anymore!

Images courtesy of Tanja Fransen, National Weather Service Forecast Office in Glasgow, Montana hook shot . . .
On July 20, 2001 line of severe thunderstorms swept through eastern Montana. The two RADAR images above each show a different aspect of one of those thunderstorms as it spawned a tornado 30 miles south of Malta. The image on the left was made using the RADAR's reflectivity mode. It shows a distinct hook echo, typical of a thunderstorm that might have a tornado beneath it. With the reflectivity mode, radar waves sent out from stations reflect off of precipitation particles, revealing where and how hard the precipitation is falling. As a severe thunderstorm develops an area of rotation (called a meocyclone), the precipitation pattern may develop the hook shape that warns meteorologists that the storm may soon spawn a tornado, if it hasn't already.

The Doppler Effect - reds and greens . . .
The image on the right was made using the RADAR's velocity mode. This mode, which also relies on precipitation (and dust) to reflect radar waves, uses the Doppler Effect to determine wind direction beneath or within a thunderstorm. RADAR waves sent to the area marked A are reflecting off of precipitation and dust particles that are blowing toward the RADAR device in Billings, whereas waves sent to area B echo off of particles that are moving away from the Billings station. The result is that waves coming back from area A have a higher frequency (shorter wavelength) than those returning from B. Computers use colors to show the difference between incoming (green) and outgoing winds (red) so that meteorologists can visualize the strong rotation beneath the thunderstorm. The National Weather Service has RADAR devices near Billings, Glasgow, Great Falls, and Missoula.

Bad day in eastern Montana . . .
Although the tornado shown on the radar images was very severe, it happened in a remote area so no one was hurt and very little damage resulted. If the tornado had swept through Billings, or any other town, the death and destruction would have been worthy of national news coverage. The same line of severe thunderstorms that spawned the twister did cause considerable wind damage (not tornadic) to power lines, grain elevators, and a pickup several miles southeast of Circle (see photo below). The storm, which had started at earlier that afternoon in Montana, finally fizzled out the next morning in Minnesota.

Update: In 2011-2012, the National Weather Service upgraded their RADAR system to utilize a new technology called Dual-Polarization RADAR.

Term: Doppler Effect

#73 - The Principle of Cross-Cutting Relationships

Which came first? . . .
This roadcut a few miles south of Cascade along I-15 illustrates one of the basic principles used by geologists to determine the relative ages of rocks. The horizontal layers are sandstones made up of sediment laid down near the coast of a shallow sea that was present here millions of years ago. The darker rock that cuts vertically through the layers of sandstone is type of igneous rock formed as magma solidified beneath the surface. These types of igneous formations, called “dikes,” are common in the Cascade area.

Relative age . . .
Since the igneous rock “cuts across” the sandstone layers, geologists conclude that the sandstone was there first. In other words, “relative” to (compared to) the igneous rock, the sandstone is older. This is called the “principle of cross-cutting relationships” . . . If a crack, a fault, a vein, a dike, etc. cuts across another rock, then that which “cuts across” happened after the older rock was formed. For example a crack through part of a sidewalk could have only happened after the sidewalk was built.

Absolute age . . .
Determining relative ages of rocks is important, but where igneous rocks are found radiometric dating techniques can provide a more accurate age. The Ar 40/Ar 39 and K/Ar (potassium/argon) methods can be used for dating the type of igneous rock shown in the photo. Geologists have determined the igneous rocks in the Cascade area solidified about 75 million years ago. Based on this “absolute age” of the igneous rock, its fair to say that the sandstone shown in the photo is over 75 million years old.

terms: inert, radioactive decay

#74 - Glacial Striations on Snake Butte - Ft. Belknap Reservation

Click on photo to enlarge.

That's going to leave a mark.
This photo, taken on Snake Butte in north-central Montana, shows scratches that were made as the continental glacier flowed across here during the last ice age. Large rock fragments stuck to the bottom of the ice caused the gouges, which are called striations.

How to track a glacier.
Striations help determine which direction the ice was flowing as it moved across an area. Striations caused by the continental glacier that grew southward from Canada during the last ice age help geologists locate "centers" where the ice started to grow from before it merged to form the single ice sheet that covered Canada. In fact, striations found in various parts of Canada indicate that there were three places in northern Canada where snowfall accumulations contributed to the ice sheet that eventually reached Montana. Striations on Snake Butte indicate that the glacier flowed toward the southeast as it flowed over the butte – probably because the Bears Paw Mountains (several miles southwest of here) forced the ice in that direction.

How far south?,br> The huge glacier left other clues that help geologists determine how far south it advanced. For example, large boulders of granite and gneiss brought from Canada by the ice can be found as far south as the Missouri River in central and eastern Montana. As the glacier flowed across Snake Butte, it scattered huge rocks from the butte in a line extending almost 50 miles to the southeast, confirming the flow direction indicated by the striations. In some places ridges of till, called "terminal moraines", mark the farthest advance of the ice. The town of Polson is built on one of these moraines. The Polson moraine formed as ice at the end of a glacier melted, dropping any rock material that it was transporting. Moraines in southern Illinois indicate that the continental glacier grew much farther south in the Midwest than it did in Montana.

Term: till

Below: A closer look at the same striations shown in the top photo.

Click on photo to enlarge.

#75 - Marlin the Meteorite Man from Malta, Montana

Photo courtesy of https://meteoritecar.com/history/. That's Marlin, holding the famous Peekskill Meteorite in 1992. Michelle Knapp (second from right) with her family, along with the original purchasers of the Peekskill meteorite: Dr. Jim Schwade (far right), Marlin Cilz (center), and Ray Meyer (center rear).

Catch a falling star!
One of the most unique Earth Science related businesses in the country is the Montana Meteorite Laboratory located in the shop of Marlin Cilz in Malta. Marlin, who used to own one of the largest personal collections of meteorites in the world, established the part-time business that specializes in cutting and preparing meteorites for display. Although the surfaces of meteorites can be interesting, what's inside can be quite spectacular. So, finders and collectors from as far away as South Africa send their meteorites to the Montana Meteorite Laboratory where Marlin uses special saws and other equipment to slice and etch the specimens, revealing their beautiful interior.

Meteorite or "meteorwrong"?
The piece that Marlin is holding in the photo is from a 38 lb. iron meteorite that was brought to him by a family from Roundup, Montana. The family had been using the unusually heavy "rock" as a doorstop for a building on their ranch for several years before they found out about Marlin. He confirmed that it was a meteorite. A closer view of a similar meteorite (below) shows the unusual pattern of iron and nickel crystals that Marlin brings out by etching the freshly cut surface with a strong acid.

Meteoroids, meteors, meterorites?
Meteorites are simply pieces of rock and/or metal from space that have reached the Earth's surface. When they are out in space they are referred to as a "meteoroids". When meteoroids get close to the Earth, or vice versa, our planet's gravity pulls them in. Then as they are traveling through our atmosphere at anywhere from 8 to 44 miles per second, the friction causes tremendous heating, and the rock begins to burn up. Most of these "shooting stars", believed to be about the size of a grain of sand, vaporize before hitting the Earth. But occasionally larger ones make it through. The largest one ever found in the U.S.A. was a 15.5 ton iron meteorite discovered near Willamette, Oregon in 1902. It now sits in the American Museum of Natural History in New York City.

Annual meteor showers.
On dark, clear moonless nights, you should be able to 3 to 4 meteors per hour. But there are certain nights each year that Earth experiences "meteor showers", causing the number of meteor sightings to rise significantly. One of the best showers happens from August 9th to 13th when Earth's orbit crosses the path of Comet Swift-Tuttle. As Swift-Tuttle approaches the Sun (once every 130 years) some of the ice evaporates, leaving behind a trail of rocks that were embedded in the comet. Then as Earth passes through this debris every August, we experience the showers.

Everything you ever wanted to know.
It just so happens that the best book for the amateur who wants to learn more about meteorites also has a Montana connection. Rocks From Space by O. Richard Norton, is published by Mountain Press Publishing of Missoula, Montana. The book includes a photo of Marlin holding the famous Peekskill Meteorite that hit a car in Peekskill, New York on October 9, 1992. Before crashing into the car, the meteor was caught on video by several people back east who were recording high school football games when the burning stone streaked across the sky. Marlin and two other collectors combined to purchase the stony meteorite. In addition to Rocks from Space, another great source of information is the Meteorite Market web site.

NOTE: There is a great 10-minute segment on the "Backroads of Montana" program titled "Gravity's Pull" (PBS). CLICK HERE to watch it on Youtube. The segment about Marlin starts at 26:43. Alslo, if you pass through Malta, stop in at the Phillips County Museum to check out some of Marlin's meteorites as well as a complete fossil of a duck-billed dinosaur.

Terms: asteroid, comet

#77 - Glacial Trough south of Red Lodge, Montana

Click on photo to enlarge.

Scenic point . . .
I took this photo along the Beartooth Highway about 20 miles southwest of Red Lodge (as the crow flies) and 5 miles north of the Wyoming border. A portion of the highway is visible just to the left of the photo’s center. The Beartooth Highway and the Going To the Sun Road in Glacier National Park are two of the most scenic drives in the USA. Gimmie a ”V” - Or is that “U”? . . .
The valley shown in the photo is a great example of a “glacial trough” sculpted by an alpine glacier that flowed though here during the last ice age over 10,000 years ago. Valleys carved by rivers in mountainous areas tend to have distinct V-shapes, whereas those shaped by glaciers tend to be U-shaped. During the ice ages glaciers formed in Montana’s high mountainous areas near the upper portions of river basins and then flowed down through river valleys. Along the way the glaciers plucked rock material from the valley walls, widening and re-shaping them as they plowed through.

Where melting equals movement . . .
Eventually, as these glaciers flowed out of the mountains they reached elevations where they began to melt back as fast as they were flowing downward. While the climate was stable, the front (toe) of the glacier stayed in one place for decades. As a result any rocks that were embedded in the ice and stuck to the bottom or the sides of the glacier were deposited there, forming a ridge of rock material called an end moraine. For the glacier that widened this valley the moraine is located about 12 miles north of Red Lodge. Since we are in what paleoclimatologists refer to as an interglacial period, a river (Rock Creek) once again occupies the U-shaped trough.

Don’t be in such a hurry! . . .
The Beartooth Scenic Highway, also known as (the Cooke City Highway”) is a drive that every Montanan should take. If you don’t stop, it takes bout 2.5 hours to get from Billings to Cooke City. But don’t hurry! Be sure to take several stops along the way, including the beautiful “scenic turnout” where this photo was taken from. The turnout has a nice parking lot, restrooms, and a walkway that offers breathtaking views of the valley below and the surrounding Beartooth Plateau. The short walkway is constructed primarily of gneiss, a rock formed as granite is changed by heat and/or pressure. To take the highway, turn south at Laurel and continue south through Red Lodge.

Terms: interglacial period, alpine

#79 - Evaporation to Blame for Microbursts

Photo courtesy Tracy O'Connor, Poplar Airport Manager

Although Montana does occasionally experience tornadoes, a more common source of destruction associated with thunderstorms in our state is something called a "downburst" (smaller ones are called "microbursts"). These are exceptionally strong downdrafts that, upon reaching the Earth's surface, diverge horizontally like water streaming from a garden hose nozzle that has been aimed at the ground. Downbursts can occur with or without rain. Their straight-line winds can blow down trees, flatten crops, and destroy buildings. Sometimes downburst damage is wrongly blamed on an unseen tornado.

Deadly Microburst of 2010 . . .
A series of thunderstorms that moved through north-eastern Montana June 16, 2010 produced the microburst that flattened the modular home (shown in the above photo) 3 miles east of Froid, killing one of the inhabitants. The home was lifted from its foundation, thrown 30 feet to the north-northeast and flipped over. A man and a woman were in the home when the microburst hit at about 9 pm. The lady, who was found over 250 feet north-northeast of the main debris area, died and the man was hospitalized with injuries that included broken bones.

Experts estimate wind speeds needed to cause such destruction were in the 110 to 125 mph range. Unlike the 2005 storm that affected Culbertson, the worst damage from this event was isolated to a small area east of Froid. Neighboring farms had no significant or obvious damage. According to Tanja Fransen of the National Weather Service Forecast Office in Glasgow, microburst winds of 50-70 mph occur between 10 to 15 times a year in eastern Montana, with more devastating winds occurring once or twice a year. However, these usually go unnoticed due to the rural nature of the region. There simply aren't many people or buildings in this part of the state.

Understanding downbursts and microbursts is "no sweat". . .
Downbursts are caused by the same thing that happens every time a molecule of water evaporates from your skin. As sweat evaporates it helps cool your body because the water molecules absorb heat as they change from liquid to vapor. The same thing can happen with a thunderstorm. As rain falls through very dry air, much (or all) of the rain may evaporate. As this happens the water molecules absorb heat from the surrounding air, making that air much colder. . . . The more evaporation, the colder the air gets. Anyone who has ever opened a refrigerator door should know that colder air is heavier than warmer air. As this air (cooled by the evaporation of rain) gets heavier, it plunges toward the ground like a lead weight. When the microburst reaches the ground surface winds may exceed 150 miles per hour.

Watch the Latent Heat Captured on Video to see how a phase change can release heat.

The smaller ones can be more dangerous . . .
Technically, scientists refer to the smaller downbursts as "microbursts". Downbursts, which can also be caused by evaporation due to dry air that rises into a thunderstorm, are classified according to size and duration. The smaller ones (microbursts) typically have a path of destruction that is 2.5 miles or less, can have winds approaching 170 m.p.h., and last less than 10 minutes. Microbursts are especially dangerous at airports where there small size defies detection and they play havoc with planes that are trying to land. Larger downbursts are called "macrobursts", or simply "downbursts."

Patterns of destruction . . .
Tornado scientist Ted Fujita discovered downbursts while surveying starburst patterns of wind damage as he was flying over an area in West Virginia after a tornado outbreak in 1974. (See photo at bottom of this page.) Fujita recognized that some areas displayed damage that caused by straight-line winds extending out from a center area, much different from the chaotic messes caused by tornadoes. As a young man Fujita had observed first-hand a similar pattern of damage in the aftermath of Hiroshima and Nagasaki where the first nuclear bombs had been dropped to end WWII.

CLICK HERE to watch a video of a microburst that happened near Tucson, Arizona in the summer of 2015.

Dr. Fujita . . .

1. Fujita came to the USA because he was fascinated with tornadoes. Among other things he developed the Fujita scale for rating tornadoes based on the damage they cause. The F in F-5 stands for Fujita.

2. Fujita's discovery of downbursts changed the way pilots land planes in the presence of thunderstorms. These changes have probably saved thousands of lives.

3. With some thunderstorms you may notice that the rain isn't making it all the way to the ground. This rain that falls, but evaporates before reaching the ground, is called virga.

Term: virga

#80 - Rhinos in Nebraska? Geysers in Billings?

12.5 million years ago: A "supervolcano" erupts . . .
This photo shows one of the fossil rhinoceroses that can be found at an extraordinary fossil site in north-central Nebraska. The site, called "Ashfall," features about 100 rhinos, along with horses and other animals that died as result of a volcanic eruption in Idaho about 12.5 million years ago. The eruption produced a tremendous cloud of ash that descended onto a savanah that was located in the prehistoric Midwest. As the lungs of animals filled with ash, they sought relief at a waterhole where they eventually died and were covered with several feet of ash.

Geologists have recently determined that the age and chemical composition of the ash in Nebraska matches those of an ancient volcano (caldera) in southwest Idaho called Bruneau-Jarbridge (see map below). As it turns out, a huge plume of magma from Earth's mantle, called a "hot spot," caused the volcano. The hot spot has been erupting every 600,000 years or so as the North American plate moves over it, leaving a trail of calderas across southern Idaho. Since its first known eruption 16.5 million years ago, the hot spot has blown about 100 times, including an eruption 2 million years ago that put out enough ash to bury New York state to a depth of 65 feet.

FFWD to Today: Yellowstone Park . . .
The hot spot that caused the cataclysmic eruption in southwest Idaho 12.5 million years ago, now sits beneath Yellowstone Park. Heat from the hot spot causes all of the Park's geysers, mud pots, and hot springs. Geologists estimate that the magma chamber beneath Yellowstone is about 45 miles across and 8 miles thick.

The future: Geysers in Billings? . . .
Look at the map below, and consider this . . . If the Earth's crust continues to move over the hot spot at the same rate and direction that it has been for the past several million years, then a few million years from now folks from throughout the world may be traveling to the Billings area to see spectacular geysers, hot springs, and mud pots.

More about Yellowstone from A Short History of Nearly Everything by Steve Bryson . . .
If you're interested in learning about the history of scientific discovery, you'll like this book. You don't need to be a scientist to understand it.

1. Yellowstone and other "supervolcanoes" do not have cone-shaped peaks like Mt. St. Helens or Mt. Rainer. Instead, all that's left after a supervolcano explodes is a crater, called a caldera, which is often covered with rubble, ashflows, and/or lava. The Yellowstone Caldera is more that 40 miles across, much too big to be noticed from anywhere on the ground.

2. Pressure from the magma beneath the surface, causes Yellowstone Park and the surrounding area to be raised about 1,700 feet higher that it would otherwise be.

3. The ash from the last eruption (about 600,000 years ago) covered all, or parts, of nineteen states plus parts of Canada and Mexico.

4. Between 1924 and 1984, and area of several dozen square miles in the central part of the Park has bulged over 3 feet.

Term: supervolcano

#84 - Saline Seep makes Soil Too Salty for Crops

Photo courtesy of Montana Salinity Control Association

Too salty . . .
This aerial photo was taken over Interstate Highway #15 near Power, Montana (25 miles northwest of Great Falls). The white patches to the right of the highway are areas where the soil has been damaged by saline seep, a problem that has ruined more than 300,000 acres of farmland in Montana. The word "saline" refers to the salts (mostly sodium and magnesium sulfate salts) that build up at the surface, making it difficult for crops to grow there.

In a nutshell . . .
The diagram below illustrates how saline seep typically occurs. Water soaks into the ground at the "recharge area". Excess water that is not absorbed by plants moves (percolates) downward through the soil. On its way it dissolves (leaches) mineral salts. In the diagram, the salt-laden groundwater reaches an impermeable layer and then migrates to a lower area where the water table is at the surface. At this "discharge area", the water evaporates, leaving the salts behind as a white crust on the surface.

"Summer Fallow" is the culprit . . .
Although sodium and magnesium sulfates (salts) occur naturally, saline seep is usually not natural occurrence. In Montana the problem is often related to a "crop-fallow" system of farming. With this type of farming, every other year a strip of land is kept barren of vegetation by plowing and/or using herbicides in order to allow soil moisture to build up and eliminate weeds. On these strips, called "summer fallow", there are no plants to absorb the water from rain or melted snow, so it more easily soaks through the soil, leaching salts along the way and causing an elevated water table.

Term: leachate

#85 - Blocking High Forced Storms Away From Montana

High means dry. . .
Montana experienced an unseasonably warm, dry February in 2005 as a result of an area of high pressure that parked itself over the northwestern USA for much of the month. Areas of high pressure, sometimes called "high pressure systems", or just "highs", are places where air is sinking. As it sinks, the air is compressed and warmed, making high pressure days more likely to be clear with sunny days, cold nights, and very little precipitation. Weather systems generally move across Montana from west to east, typically passing through over a period of a few days. But the high of February 2005 stayed put for weeks, causing the jet stream and the storms that it guides go around Montana. High pressure sytems that do this are sometimes referred to as "blocking highs".

Back in the groove . . .
Finally in March the high dissipated and storms began to move across Montana once again, bringing much needed moisture to the state. The image above shows two major storms, one that affected the eastern USA and the another that brought significant snow to our state. Both storms were mid-latitude cyclones, usually just called "low pressure systems" (or "lows"). In disturbances such as these, air flows counterclockwise, rising as it spirals toward the center (L on image below). Whenever air rises, it cools by expansion, helping clouds (and precipitation) to form. Low pressure systems usually feature a fairly distinct cold front (blue, spiked line) where cold air is pushing into warmer air, and a less distinct warm front (red, bumped line) where warmer air is pushing into and over colder air. Both warm and cold fronts force the warmer air to rise and cool by expansion, helping clouds to form. Quite often the clouds in a low pressure system form a comma shape, especially in the eastern USA where there is more humidity (Gulf moisture) and no tall mountains to disrupt the motion of air within the system.

Watch The Ultimate Cloud Demonstration (3.5-minute video) to see the relationship between pressure and clouds.

Eyes in the sky . . .
Both images on this page were taken by N.O.A.A.'s GOES-East, a geostationary satellite that provides a view of the lower 48 states and the western part of the Atlantic Ocean. The GOES-West allows meteorologists to monitor storms over the Pacific as they approach the USA. Both satellites can produce three types of images, including infrared, water vapor, and visible. Infrared images, like the one at the top of this page, are important because they show where the coldest cloud tops are, the ones most likely to be causing precipitation. Also, infrared images do not depend on daylight as visible images do. At the time the above image was made it was snowing in Montana and there was significant rain and some areas of severe weather (red) in the east.

Below: This "visible" image shows where there were clouds as the two storms made their way across the country. I estimated the location of the fronts and the direction of the winds (green arrows), and then added them to the image.

Just thought you'd like to know . . .
N.O.A.A. stands for National Oceanic and Atmospheric Administration. G.O.E.S. stands for Geostationary Operational Environmental Satellite.

Term: geostationary

#82 - The Arrival of Captain Lewis at the Great Falls of the Missouri, June 13, 1805

Painting by Charles Fritz, Oil on Canvas 42" x 65"

An agreeable sound . . . On the morning of June 11, 1805 Captain Lewis and four men set out from a fork in the Missouri River (now referred to as “Decision Point”) near Loma, Montana in search of “the great waterfalls” that the Indians told them to expect. Clark stayed with the main party and attended to Sacagawea who was ill. The significance of finding the falls is that it confirmed that they had taken the correct fork in the river. Fritz’s painting shows Captain Lewis as he first gazed upon what we now call “The Great Falls” on June 13, 2005. Lewis wrote about the discovery in his journal:

I had proceed on this course about two miles with Goodrich at some distance behind me whin my ears were saluted with the agreeable sound of a fall of water and advancing a little further I saw the spray arrise above the plain like a collumn of smoke which soon began to make a roaring too tremendious to be mistaken for any cause short of the great falls of the Missouri. Here I arrived about 12 Oclock. From the reflection of the sun on the sprey or mist which arrises from these falls is a beautifull rainbow produced which adds not a little to the beauty of this majestically grand senery. (Lewis didn’t have spell-check on his laptop.)

A set of five . . .
The Great Falls (shown in the painting) were actually the first of five waterfalls encountered by the explorers as they journeyed through an 18-mile stretch that included the area now occupied by the city of Great Falls. Although each of the waterfalls has its own name (Great Falls, Crooked Falls, Rainbow Falls, Colter Falls, Black Eagle Falls) the set of five waterfalls is referred to as “the Great Falls of the Missouri.”

Geology caused the falls . . .
Each of the falls is caused by the presence of an especially tough layer of sandstone unit in the Cretaceous Kootenai Formation. A “formation” is a large area where a particular type of sediment was deposited. The Kootenai Formation consists of sedimentary rocks formed from sands and silts that accumulated in a shallow lake, or as rivers emptied into a marine embayment roughly 115 million years ago. The formation includes alternating layers of siltstone (shale) and sandstone. The city of Great Falls is built on the crest of a gentle fold known as the Sweetgrass Arch. As the arch has been worn down, the sandstone has been more resistant to weathering and erosion, causing the formation of the set of waterfalls that drop the Missouri River more than 500 feet over 18 miles.

Above right: This aerial photo, provided by Jim Wark of Airphoto - North America, shows the same falls featured in the painting. Ryan Dam, which can be seen just above the waterfalls, is one of five hydroelectric dams that have been built along the Great Falls of the Missouri. Ryan Dam is about 8 miles northeast of the city of Great Falls.

A month of hard work . . .
The waterfalls on the Missouri River proved to be a huge obstacle for the Corp of Discovery. It took the expedition a month to move everything upstream above the last falls – just 18 miles away. This portion of the journey is known as “The Portage.”

Term: portage

#83 - Grasshopper Glacier North of Yellowstone Park

Photo courtesy of Alexandre Lussier, Dept. of Physics, Montana State University

One of the most unusual "Earth Science places" in Montana is Grasshopper Glacier located 70 miles southwest of Billings (10 miles north of Cooke City). The Glacier, which sits at 11,000 feet in the heart of the Beartooth Mountains, takes its name from the millions of grasshoppers embedded in it. Entomologists identified the hopper as a species of migratory locusts (Melanoplus spretus) commonly called "Rocky Mountain Locusts".

Migration gone bad . . .
Centuries ago this species of locust was found in large numbers throughout the West. Scientists believe they became embedded in the ice when migrating swarms, passing over the high mountains, became chilled or were caught in a severe storm and were deposited on the glacier. As snow built up over decades, the grasshoppers were buried deeper and deeper. Then as the climate in the area has warmed over recent centuries, melting of the snow exposed the embedded grasshoppers, and they were discovered. Until recent years, visitors could dig perfectly preserved specimens from the ice. However, years of light snow during the winter and thawing during the summer months have exposed many of the grasshoppers to decomposition.

University of Wyoming study . . .
Fortunately there are other glaciers in the Rockies that also contain swarms of grasshoppers, and in the 1990s a team led by Jeffrey Lockwood, Professor of Entomology at the University of Wyoming, found one in Wyoming that contained intact grasshoppers. The team used radiocarbon dating to determine that the swarm was blown into the mountains in the early 1600s.

Glacier, or Snowfield? . . .
In order for a glacier to form there needs to be build-up of snow over many years. At lower elevations where most of us live, all of the snow that falls in the winter melts in the spring. At high altitudes that isn't always the case. For example, an average of 8 feet of snow might fall every winter, but only 3 feet melt away every summer, leaving a build-up of 5 feet of snow. When this goes on for decades these annual 5-foot layers form, one on top of the other, and begin to compress the layers beneath. As a result the snow nearer the bottom is changed into ice, and a glacier is born. Apparently not everyone is convinced that has happened with Grasshopper Glacier. Not enough snow built up to transform the bottom layers into ice, so technically Grasshopper Glacier is simply a "snowfield" that has been around for a very long time. But don't expect a name change anytime soon . . . "Grasshopper Glacier" has a much nicer ring to it than "Grasshopper Snowfield" does.

NOTE: In 2000, Grasshopper Glacier was approximately 1 mile long and 1/2 mile wide. Scientists believe it was over 4 miles long at its peak during colder times.

Below: Robert Grebe took this photo of Grasshopper Glacier in September of 2010.

Term: entomology