#97 - Wind Generators near Judith Gap

Click on photo to enlarge.

January of 2006 marked the completion of Montana's first major wind power project. Located between Judith Gap and Harlowton (between Billings and Great Falls), the project includes 90 wind- powered generators, each capable of producing enough electricity for 300 to 400 homes. The generators are owned by a Chicago based company called Invenergy, which sells the electricity to Northwestern Energy. Each generator stands about 260 feet tall in order to tap the stronger winds found farther from the surface.

Why here? . . .
According to an Invenergy spokesman the winds in January of 2006 averaged 42.6 miles per hour. But these strong, steady winds weren't the only factor that made this site appealing. The site is also close to a major transmission line that runs between Great Falls and Billings; two population centers that represent a significant demand for power.

How to make electricity . . .
A wind-powered generator works like a fan in reverse. Instead of using electricity to move air like fans do, wind generators use mving air (wind) to generate electricity. Here's how it works. . . . To make (generate) electricity, you need three things: a magnet, a wire, and motion. If you take a magnet and move it in close proximity to a wire, this causes an electrical current to flow within the wire. Within a generator, wires and magnets are organized so that a current will be produced in the wires if motion is provided. Generators can be designed to utilize all sorts of motion ranging from the peddling motion of a bicycle to the motion of water through the bottom of a dam. At coal-fired plants, coal is burned to heat water. As the water changes to steam it shoots through a turbine, providing the motion. With wind generators, the wind turns propeller-shaped turbines to generate electricity.

CLICK HERE to watch a short wind generator demonstration (less than 2 minutes).

Pros and cons . . .
Over half of the electricity used in Montana comes from coal-fired generators, primarily those located at Colstrip in the southeastern part of the state. Dams are the other primary source. A big advantage of wind-generated power (and hydro-power) is that there are no emissions. Coal-fired plants emit carbon dioxide (a major greenhouse gas) as well as sulfur dioxide and mercury. One problem associated with wind generators is that power companies, such as Northwestern, have to buy power from other sources to keep the power flowing when the wind isn't blowing. The short-term nature of these additional sources of electricity cause them to be more expensive.

Windfall for county . . .
Another plus for the area is the revenue (income) that the project will provide for Wheatland County. The county expects to get over $750,000 in "impact money" over the next three years to offset the impact of construction. Projects such as this have an "impact" on schools, roads, water and water systems, fire departments, etc. Impact dollars help counties pay for these services. Also, the wind generators will continue to generate tax dollars for the county and state for years to come.

Term: barotrauma

Below: A turbine blade on display in the small community of Judith Gap, Montana.

#98 - (Not) Chalk Buttes near Ekalaka

Photo by Gwenith Schultz

A “misnomer” . . .
This photo shows one of the Chalk Buttes located in the remote southeastern corner of the state, about 10 miles southwest of Ekalaka. Although they are called Chalk Buttes, they are not made of chalk, but rather an especially white sandstone. “Chalk” is actually a soft white to gray limestone composed of the hard coverings of microorganisms and some bottom dwelling animals such as ammonoids and pelecypods in a matrix of finely crystalline calcite. As the organisms die their hard parts (shells, etc.) accumulate on the sea floor where they are eventually crushed beyond recognition by layers deposited above them. If the material becomes so compacted that it is hard, geologists would simply call it limestone. Less compaction will result in the softer (less durable) chalk. England’s White Cliffs of Dover are a great example of chalk.

When dinosaurs ruled Montana . . .
The Chalk Buttes of southeastern Montana are made of sandstone deposited in the later part of the Cretaceous Period, which ended about 65 million years ago. The Chalk Butte sandstones are part of the Colgate Formation, which is found throughout much of eastern Montana just below the Hell Creek Formation; the last layers of sediment deposited before the extinction of the dinosaurs at the end of the Cretaceous Period. Evidently the sand that makes up the buttes was deposited in some sort of valley (basin), west of the shrinking interior seaway that split prehistoric North America in two.

Chalk it up to the rock cycle . . .
In order for sand to become rock (lithification) many processes happen over a long period of time. First the sand (usually pieces of quartz) originates from pre-existing rock such as granite. As the granite breaks down (weathering) the sand is transported, often by running water (erosion), to a basin where it is deposited (deposition). As millions of years go by the layers of sand may experience many more “diagenic” processes, including compaction, dewatering, cementation, dissolving of certain mineral components, replacement of minerals by other mineral phases, heat and pressure of deep burial, etc. Not only did these processes change the sand into sandstone, but they also bleached the rock giving it its chalky appearance.

term: diagenesis

#99 - Lewis and Clark Pass on the Continental Divide

On their return trip from the Pacific in 1806 the Lewis and Clark Expedition split up. Clark’s party set out to explore what is now southern Montana, while Lewis took nine men on a more northerly route to investigate a short cut over the mountains and then explore north-central Montana. The Corps learned of the short cut from Indian tribes west of the divide who used it to travel east of the mountains where they could hunt buffalo.

Familiar landmark . . .
On July 7, 1806, as the Lewis party reached the pass shown in this photo they recognized a landmark from their westward journey through the Great Falls area during the previous summer . . . a prominent butte that they had named Fort Mountain (see photo at bottom of page). It was a welcome sight, not only because it meant they were on their way home, but also because it meant that once again they would be able to enjoy an abundance of buffalo meat.

If they had only known . . .
The explorers soon realized that if they taken this route on their route to the Pacific they would have saved 50 days, avoiding one of the most difficult segments of their journey. After crossing here, the men pursued buffalo and other game, and explored the area northwest of modern day Great Falls, before returning to the Missouri river near the Great Falls of the Missouri.

A famous line . . .
The blue line on the photo marks the approximate location of the Continental Divide. A lower place that offers an easier crossing of a divide or mountainous is referred to as a “pass”. This one is named “Lewis and Clark Pass” even though Clark was never there. Water that runs off east of the divide will end up in the Gulf of Mexico by way of the Missouri and Mississippi Rivers, whereas runoff west of the divide flows toward the Pacific via the Blackfoot, Clark Fork, and Columbia Rivers.

Term: runoff

#100 - Eureka Drumlin Field

Above: This Google Earth image shows a portion of the Tobacco Valley in the extreme northwestern corner of Montana. Several tadpole-shaped (teardrop-shaped) hills can be seen in the area between Eureka and the Canadian border. The hills resemble a school of tadpoles swimming toward Canada.A closer view of "A" is shown at the bottom of this page.

One of a kind . . .
The strange hills are called drumlins, and the group shown above, called the "Eureka Drumlin Field", is the only one of its kind in Montana. The swarm consists of over 300 drumlins in an area of 175 square miles around Eureka. The drumlins vary in length from 1,300 feet to 8,000 feet.

Unsolved mystery . . .
A glacier flowed southward through this valley during the last ice age, advancing as far as Polson (about 90 miles from Eureka). As the ice pushed through the area it pulverized bedrock and sediments, forming a mixture of boulders, cobbles, sand, sand and clay called "till". This unsorted mixture of rock materials is what the drumlins are made of. Glaciers transport and eventually deposit till in shapes called moraines, kames, and eskers. In fact the town of Polson sits atop a moraine that helped Flathead Lake to form. Although geologists have a reasonably good understanding of how glaciers build moraines, kames, and eskers, the processes that form drumlins remains somewhat mysterious. It is also poorly understood why drumlins form in some glaciated areas and not in others.

Two schools of thought . . .
Glaciers remove and transport (weathering, erosion) rock materials from some places, and they deposit these same rock materials in other places (deposition). . . Cirques, u-shaped valleys, and horns are all "erosional features", whereas moraines, kames, and eskers are all "depositional features." Some geologists suggest that drumlins are erosional features, formed when a glacier flowed over deposits of rock material left by an earlier glacier. Others think that drumlins were deposited and shaped simultaneously as a glacier flowed over till that it had transported. Both schools of thought agree that drumlins form beneath an actively flowing glacier, and that the more pointed end of the drumlins indicates the direction that the ice was flowing (toward the south in the case of the Eureka drumlins).

A Bottleneck to blame? . . .
One theory about the formation of the Eureka Drumlins is that the glacier slowed or stagnated upon reaching a narrow portion of the valley 10-15 miles south of Eureka. During warmer periods within the ice age, melting from the bottom and/or front of the glacier may have deposited a significant amount of till in the area. Then, during colder periods the glacier would have started to advance once again, causing thicker ice to flow over the deposits. Pressure from the weight of this somewhat thicker ice may have shaped the rock material into the distinct tadpole-shaped drumlins. Since the till was not deposited and shaped simultaneously, this theory suggests that the Eureka drumlins are "erosional" landforms.

Term: till

FYI: 1. The word drumlin comes from the Irish Gaelic word druim, which means "ridge". Perhaps the most famous drumlin is Bunker Hill in Massachusetts.

2. The valley referred to in the text above is known locally as the Tobacco Valley (or Tobacco Plains). It is actually part of "The Rocky Mountain trench", which extends from the St. Ignatius 1,000 miles northwest to the Canada's Yukon Territory

Source: Anderson, Carol. "The Eureka Drumlin Field: Possible Origins." Senior Thesis: University of Montana. June 5, 1978

Below: A closer view of the area labelled "A" in the image atop this page.

#101 - A Remnant of the Last Ice Age

Photo by Jim Rea, Courtesy of Fish, Wildlife and Parks

Note: The Brush Lake article was written by Doug Smith of Dagmar Montana. He allowed me to make some changes so the article would be similar to other pages on this web site. The article appeared in the Queen City News and other newspapers as part of a weekly column contributed by Rick Graetz.

Treasure State Gem . . .
Aside from its distinctive aquamarine blue color, Brush Lake near Plentywood in the northeastern corner Montana looks like many other lakes on the northern Great Plains. However its depth, chemistry, biology and hydrology stand alone in making this a unique body of water.

Sediments tell the story . . .
For millions of years, before the last ice age, the Missouri River turned north just east of Poplar and flowed northeast to Canada's Hudson Bay. During the last ice age the ice sheets spread south grinding up Canadian bedrock and carrying it south to cover the northern portion of Montana and filling in the old river valleys. First the river valleys were filled with lake bottom clays from the dammed up rivers, then glacial till when the glaciers arrived, and finally with outwash sand and gravels when the ice retreated.

Was Paul Bunyan here? . . .
As the climate warmed and the ice front melted back to the north it continued to send tongues of ice down the old valley, leaving a great block of ice a mile long, a half mile wide and hundreds of feet thick where Brush Lake now sits. The melting ice front continued to wash down great volumes of sand and gravel to bury the huge piece of ice. Eventually a spruce forest grew over the buried, slowly melting ice block (diagram). When it finally melted completely, it left the depression that would become Brush Lake. The spruce trees ended up at the bottom of a 100-foot deep lake. Minnesota is famous for lakes formed this way. Geologists call these depressions "kettles", but legend has it that those in Minnesota are footprints left by Paul Bunyan and Babe (his blue oxen).

Strange hydrology . . .
Groundwater flows easily through the buried outwash gravels and the deeper river terrace gravels. These aquifers, which are used for irrigating farmland in the area, supply Brush Lake with a continuous flow of water through large springs in the lake. Since no streams flow out of Brush Lake, summer evaporation serves as a pump to keep groundwater flowing into the lake. And since evaporation only takes pure water out, the minerals leached from the glacial gravels remain dissolved in the lake and accumulate, giving the lake its distinct color. Certain algae and bacteria thrive in this flow of mineral rich water, taking what they need to grow and deposit the carbonates (limestone) in the form of cones, florets, and reefs on lake bottom. Brush Lake's symbiotic twin is White Lake to the south. It is 4 to 6 feet lower and essentially an evaporation pan for the excess water seeping out of Brush Lake. White Lake is where all the sodium sulfate (alkali) comes out of solution and is deposited. The mineral laden water inflow, offsite evaporation and biotic action keep Brush Lake's water clear and fresh year round. It is one of the few lakes in the world where this dynamic process is found.

Brush Lake's Diary . . .
Being a deep lake (65 feet) in a closed basin, Brush Lake contains a sediment record of value to the scientific study of climate change. Since it first saw daylight 10,000 years ago, Brush Lake has accumulated 45 feet of sediments. Much like tree rings the lake annually deposits a layer of light and dark sediment (called "varves"), which can be used to construct a time line. These layers contain pollen and distinct minerals which allow scientists to determine variations in climate since the ice age.

Catching anything? . . .

Over the years attempts have been made to stock the lake with fish, but with no success. It is theorized that all the oxygen in the groundwater is tied up in dissolving the calcium rich gravels resulting in poorly oxygenated lake water. In addition, Brush Lake's water may be more similar to sea water than fresh water, making it tough for traditional sport fish to survive. That is not all bad, since Brush Lake is being developed as a water recreation area there will be no conflicts between motorboats and fishermen, and no need to worry about stepping on a fish-hook when jumping in for a swim.

FYI: Brush Lake lies within the "Prairie Pothole Region", which is so important to the well-being of waterfowl populations. Term: leached

Below: This diagram (from "Quaternary Paleoecology" by H. J. B. Birks and Hilary H. Birks) illustrates a couple scenarios that might have caused ancient trees to end up at the bottom of a kettle lake.

Trivia: Which NBA team is named after "kettles", and why does this team have that name?

#102 - No Pots? No Pans? No Problem.

Above: They might not look like much, but rocks similar to these fire-cracked pieces of quartzite played an important role in the survival of Montana's first people.

Fire-Cracked Rock . . .
Bison bones, tipi rings, arrowheads, and other artifacts are types of evidence that help archaeologists determine whether a place was used by American Indians centuries ago. These signs help identify encampments, bison kill sites, trails, and places that were significant for spiritual reasons. However, as valuable as these clues are, archaeologists claim that one of the most reliable indicators that American Indians spent time at a location is the presence of fire-cracked rocks.

These rocks are the cracked or broken pieces of stones that were used to boil water or roast meat. Fist-sized rocks were heated in fires and then transferred into hide-lined pits or other containers to boil water, or place into dry pits to roast meat. Eventually this repeated heating and rapid cooling cracked the stones, causing them to break into recognizable pieces.

Fire-cracked rocks are especially abundant near bison kill sites . . . places where bison were driven into natural or man-made enclosures, into bogs or snow-banks, or over cliffs, and then finished off with various weapons. Experts estimate there are 8-10 tons of fire-cracked rock at the Head-Smashed-In Buffalo Jump in southern Alberta, and over 3 tons at the First Peoples Buffalo Jump near Great Falls (formerly called Ulm Pishkun).

Processing the kill . . .
Hot stones were an important source of heat in "processing" areas, which were often located near kill sites. These were areas where bison were butchered, jerky was made, hides and other parts were taken, and meat and bones were roasted or boiled. It's well known that Indians depended on bison for a significant portion of their food, and for materials used to make clothing, shelters, weapons, and tools. But perhaps the most under-rated resource obtained from bison in the processing area was "bone grease".

This white fat (not marrow) obtained from the boiling of bone fragments was very valuable to the Indians as evidenced by the incredible amount of time and effort they put into removing it from the bones. Perhaps it contained important nutrients that Indians didn't get from the lean meat of bison and other animals. This fat trapped in the bone matrix of the bison was extremely important, and rocks played an important role in helping collect it.

Right: Illustration by Shayne Tolman: Courtesy of Imagining Head Smashed In by Jack Brink

Harvesting the grease . . .
Kill sites and processing areas varied, but typically bones were boiled in pits that had been dug with sticks, or tools fashioned from bones. Once the pit was dug, it was lined with a bison hide (furry side down), and filled with water, using bladders, or other containers. American Indians used rocks to crush the longer bones of the animal into pieces the size of potato chips or smaller. These were put into the water along with red-hot stones that were carried with sticks or antlers from a nearby fire. Heat from the stones cause the water to boil, liquefying the fats trapped in the bone matrix. These fats floated to the surface where they solidified as the water was allowed to cool. Finally, it was skimmed off. Much of the grease was used to make pemmican; a mixture of pulverized jerky and dried berries, held together by the nutritious grease.

Quartzite cobbles . . .
Based on the fire-cracked rocks found at the Head-Smashed-In and First Peoples sites, its obvious that quartzite was the type of rock preferred by Indians who used these sites. It was chosen despite the presence of an abundant supply of sandstone at both places, and the reality that quartzite had to be transported from other places within the region. Quartzite worked well as a boiling stone because it is a hard, metamorphic rock formed from sandstone as heat and/or pressure fused the sand grains together. In contrast, sandstone didn't hold up nearly as well, easily breaking and adding sand to the water.

Although there are few places east of the Rockies where quartzite was formed, ice age glaciers transported many different types of rocks into Montana from Canada, including plenty of quartzite. Archaeologists who study processing sites find that several different types of rocks were used, but note that Indians preferred rocks that were hard and uniform, including some metamorphic rocks, some fine-grained igneous rocks, and even some well-cemented sedimentary rocks in some cases.

Any student of science knows that materials expand when heated and contract when cooled. So, no matter what kind of rock was used, it eventually fractured from stresses caused by repeated heating and rapid cooling. Eventually the pieces were too small to be conveniently used and the fire-cracked rocks were left behind.

Below: Here the bone has been roasted and the marrow removed. Native Americans roasted bison bones and then broke them open with stones. Sticks were used to remove the marrow so it could be eaten (much like a cheese stick). Although this marrow was important part of their diet, the purpose of boiling bones was to extract another kind of fat, which some archaeologists refer to as "bone grease".

How do they know? . . .
A basic understanding of geology can be used to recognize fire-cracked rocks.

1. The rocks are out of place. The cliffs of the First Peoples Buffalo Jump are made of sandstone and there are no metamorphic or igneous rocks exposed in the immediate area. Thus, the presence of ridiculous amounts quartzite fragments (and few other types of rock) doesn't make sense in terms of natural processes such as weathering, erosion, deposition.

2. They are the wrong shape. A variety of metamorphic and igneous were carried into Montana by glaciers. However, rocks transported great distances by glaciers and/or water will be rounded, not angular like the fire-cracked rocks.

3. The breakage surfaces are not natural. Geologists (and archaeologists) know that when certain types of rocks and minerals break due to natural processes, they break a certain way. The breakage surfaces of rocks found near kill sites are clearly not natural.

Terms: archaeology, cobble, bone matrix, artifact

Sources . . .

Brink, Jack. Imagining Head Smashed In. Edmonton: Athabasca University Press, 2008.

Rennie, Patrick J. (Archeologist, Montana DNRC) Personal Interview. 6 August 2008.

Rennie, Patrick J. "The Interpretive Value of Fire-Cracked Rock." Archaeology In Montana 42.1 (2001): 65-90.

Wilmoth, Stan. (Archaeologist, Montana Office of Historical Preservation) Personal Interview. 6 August 2008.

#103 - Radiocarbon Dating Helps Archaeologists Understand Montana's First People

Above: Here is a small portion of the extensive cliffs at First Peoples Buffalo Jump near Great Falls (formerly called Ulm Pishkun). The cliff area is about 1500 meters long (almost 1 mile).

We know that ancestors of Native Americans were the first people to inhabit Montana, and we have a fair understanding of which tribes lived here, and how they lived over the past 150-200 years. White settlers, explorers, soldiers, and journalists wrote about this era, and oral accounts were passed down over generations among Indian people. However, to learn about the heritage of Montana's tribes centuries farther back in time is much more challenging because experts have to rely on types of evidence that are harder to find and more difficult to interpret.

Mother Lodes . . .
Stories, artifacts, trails, tipi rings, and rock art all offer glimpses into the lives of pre-historic Native American cultures. Another tremendous source of evidence are the numerous bison kill sites scattered throughout the region. Archaeologists have identified over 300 in Montana alone, and there are likely many more that haven't been found or reported. We know them as "buffalo jumps," however most are not cliffs, but rather places where bison were driven into natural or man-made enclosures, or into bogs or snow-banks, and then finished off with weapons. No two are exactly the same, but they often contain a wealth of evidence, including bison bones, arrowheads, tools, roasting pits, and fire-cracked rock. Below right: This diorama depicts the First Peoples Buffalo Jump. (Courtesy of Montana Historical Society)

What's the point? . . .
Two important questions archaeologists try to answer as they unearth a kill site are, "Who used this place?" and "During what span of time did they use it?" Arrowheads and spear tips, called "points," can help provide an answer to the first question. Archeologists have learned to recognize trademarks and differences between points designed by various Indian tribes and Paleoindian groups. For example, experts know that the Wahkpa Chu'gn kill site in Havre was first used by the Besant people because the bottom layer of bones contains spear points fashioned in a style unique to that culture. The Besant used a spear-like weapon called an "atlatl", whereas the Avonlea and Saddle Butte peoples, who used the site during later times, preferred the bow and arrow. At another kill site in south-central Montana one layer of bones contains arrowheads crafted by Shoshone Indians, revealing that this has not always been Crow territory.

The Carbon-14 clock . . .
To determine when a certain tribe used a kill site, archaeologists rely on radiocarbon dating (a.k.a carbon dating). Radiocarbon dating is a type of radiometric dating that is especially useful at kill sites because it can be used to date organic materials; materials that were once part of a living things (flesh, bone, wood, charcoal, seeds, etc.). Because of its relatively short half-life, the radiocarbon technique is useful only for dating things that lived within the past 50,000 years. Although carbon dating cannot be used to establish the age of points, it can be used to date organic materials found in the same layer as the points. Where bone layers haven't been disturbed it is presumed that the points are the same age as the bones they lie with.

How it works . . .
A small amount (.0000000001%) of all carbon atoms are a radioactive isotope known as Carbon-14. As years go by, these C-14 atoms gradually undergo radioactive decay, changing into Nitrogen-14 atoms. Scientists know that it takes 5,730 years for half of the C-14 to change into N-14. This length of time is called the "half-life.' If scientists find that a bone has a C-14 to N-14 ratio of 1 to1, they would conclude that the organism died approximately 5,730 years ago. If the ratio is 1:3, then two half-lives have gone by, the bone is about 11,500 years old.

Confused? . . .
Watch this 9-minute Youtube video.

According to Dr. Jack Fisher of Montana State University, the organic materials used to establish dates at the First Peoples site were wood charcoal (burnt wood from a campfire) and blowfly pupae cases. A mass of hundreds (or thousands) of blowfly pupae were found with the bones of a bison forelimb that may have been discarded with muscle tissue still present. The samples of charcoal and pupae were sent to a lab at the University of Arizona to be radiocarbon dated.

Along came the horse . . .
Radiocarbon dating of organic materials from the First Peoples Buffalo Jump revealed that it was used from about 900 AD until at least 1500 AD. The styles of points found there match those from the pre-historic Avonlea and Old Women's cultures (ancestors of more recent Indian tribes). Archaeologists aren't sure exactly when Indians stopped using the First Peoples Buffalo Jump because the upper layers of bones have never been carbon dated. However, they do note that the use of buffalo jumps generally started to decline in the 1700s with the arrival of the horse, an animal that brought many big changes to the Indian way of life.

Terms: Paleoindian, organic, isotope

#105 - Ringing Rocks in the Boulder Batholith

Rock music . . .
"Ringing Rocks" (20 miles east of Butte, Montana: Map) is one of the most unusual rock formations in the country. A similar "ringing rock" formation exists in Pennsylvania. Folks from all over travel the three-mile gravel road north of I-90 just to pound on Montana's version of "Ringing Rocks" with hammers. To find out why, watch this 2-minute video. CLICK HERE. Be sure to have your computer's volume turned on as you watch.

Nobody knows for sure . . .
Exactly why the rocks ring like bells when struck with a hammer is a mystery. The rocks do contain a significant amount of iron, which might be part of the explanation. However, the high iron content doesn't explain two other strange qualities that the rocks possess - Not all of the rocks ring when struck, and they don't ring when they are removed from the site, suggesting that the ringing has something to do with the way the rocks lay against one another. Larger flat ones seem to produce an especially impressive sound when struck.

Compared to the neighbors . . .
The Ringing Rocks are very small part (160 acres) of a mountainous region called the Boulder Batholith, which encompasses a large portion of southwestern Montana. Batholiths originate when magma cools slowly beneath the surface to form granite. Then, if the land is uplifted, less durable rocks above the batholith tend to get eroded away, exposing the granite. Although it originated far beneath the surface, the Boulder Batholith now forms the mountains between Butte and Helena where travelers can see the light-colored granite exposed in outcroppings. Although the Ringing Rocks are part of the batholith, they differ from the rocks around them in two significant ways. For one, the Ringing Rocks are an iron-red color that contrasts with the light-gray granite that surrounds them. Another difference between the Ringing Rocks and their neighbors in the batholith is their shape - Granite in the batholith has weathered to form large boulders with rounded edges, whereas the Ringing Rocks are very angular with large flat surfaces.

Born of Fire . . .
One thing that the Ringing Rocks have in common with the surrounding granite is that they are both igneous rocks (formed as magma or lava cooled). When lava cools at the surface, the resulting igneous rock is classified as "volcanic" (aka extrusive). Basalt is the most common type of volcanic rock. If the rock formed as magma froze slowly beneath the surface, the rock is described as "plutonic" (aka intrusive). Granite is the most common type. Although the granite of the Boulder Batholith and the Ringing Rock formation are both plutonic in origin, the molten material that cooled to form the Ringing Rocks consisted of a much darker mix of minerals.

Weathered, not deposited . . .
At first glance it looks like the Ringing Rocks were transported and deposited in a pile by some natural force. When rock materials are transported away from where they were formed, it is called "erosion". Although some of the rock material that made up the original mass of gabbro has been carried away (eroded), the Ringing Rocks sit in the place where they were formed. They were not transported from some place else and then deposited here. Instead the unusual shape and color of the Ringing Rocks can be attributed to "weathering" - those processes that break down the rock. Apparently the gabbro developed quite a network of cracks (mechanical weathering), exposing surfaces for air and water to do their work (chemical weathering). Weathering shaped the solid mass of gabbro into large angular pieces shown in the photo above and erosion carried the weathered rock materials away. The iron-red surface color is a result of air and water reacting with iron to form a compound similar to rust. The broken Ringing Rock below shows how chemical weathering alters the appearance of the black gabbro.

No rocks were harmed in the making of this photo.

Confusing terminology . . .
Sometimes the way geologists use certain terms differs from the way those terms are used in the media, etc. Here are some examples related to the topics covered above.

erosion = weathering + erosion . . .
The common use of the word "erosion" is understood to include both weathering and erosion. To a geologist, "erosion" and "weathering" are two separate processes. Weathering is the breaking apart of rock, either into smaller pieces, or by dissolution (being dissolved). To a geologist, "erosion" is any process that transports rock material away. Running water transporting sand, silt, clay, dissolved minerals, etc. accounts for much of the erosion that happens in nature. When we say that a tombstone has been eroded (common use), what we are really saying is that it has experienced both weathering and erosion.

granite = rock . . .
No doubt you've heard of "granite" counter-tops. Not all granite counter-tops are really granite. The word "granite" as it is used in the marketing of counter-tops means any kind of rock. So "granite" counter-tops may be made of marble, gabbro, diorite, or other kinds of rock. To a geologist, "granite" is a specific type of course-grained, light-colored igneous rock.

granitic = plutonic or intrusive . . .
The word "granitic" is sometimes used to describe a rock that was formed as magma cooled slowly beneath the surface . . . as opposed to lava cooling more quickly above the surface. In this context, "granitic" has the same meaning as "plutonic" and "intrusive". Although there is a big difference between gabbro and granite, gabbro might be described as "granitic" because it was formed beneath the surface.

Terms: batholith, outcropping, plutonic

#108 - Lost Lake Found North of the Highwood Mountains

Click on photo to enlarge.

Not that kind of lake . . .
Lost Lake, which is one of Montana's most unique bodies of water, can be found hidden below the surrounding prairie north of the Highwood Mountains, northeast of Great Falls. The rocks and 250-ft. cliffs tell of a fascinating past, including a time when an ancient sea covered the area, an episode of volcanic activity, and a more recent period when ice age floods shaped the landscape. IMPORTANT: Lost Lake is on private land and only accessible by permission

Something has to give . . .
The Missouri River once drained toward the Hudson Bay, but that all changed with the arrival of the ice ages, and things in central Montana got really interesting when the ice reached the Highwood Mountains (15,000 to 20,000 years ago). There, the continental glacier pushed up against the Highwood Mountains, blocking the flow of the ancient Missouri River and causing the formation of Glacial Lake Great Falls. The lake filled with melt-water and eventually reached a level high enough to flow over or even burst the dam. The overflow flowed along the edge of the ice sheet through the area north of the Highwoods across existing drainages, carving a channel known today as the Shonkin Sag. Today the Shonkin Sag is a wide, deep valley with scattered brackish lakes that winds its way between the small towns of Highwood and Square Butte (south of Geraldine). However, Lost Lake is not part of the Sag's main channel. There are many unanswered questions about the area, but it is clear that at some point (perhaps several times) the flood-waters rushed across the Lost Lake area as well. The water carved the the cliffs (shown in the photo below), which would have hosted tremendous waterfalls - much higher than those found at Niagara Falls today.

Black and white . . .
The lighter-colored rocks seen in the cliffs around the lake are layers of sandstone - part of the Eagle formation, made from sands deposited during the late Cretaceous Period (over 65 million years ago) when the Western Interior Seaway inundated North America. Dinosaurs wandered along its shores and coastal plains. The Rimrocks of Billings are part of the same formation. The dark cliffs and stripes between the sandstones are igneous rocks, formed as magma cooled underground. Some molten rock did make it to the surface as lava. In fact, many of the mountain ranges in central Montana, including the Highwoods, owe their existence to a time when volcanoes were active in central Montana from 80 to 40 million years ago. The Highwood Mountains are what geologists refer to as a volcanic pile (all that is left of a volcano after millions of years of erosion). The Bear Paws south of Havre, the Elkhorns south of Helena, and the mountains between Craig and Cascade are some of the other remnants of this period of volcanism.

About those stripes . . .
Whenever there are active volcanoes in the area, there is bound to be magma moving around below the surface as well. In some cases the magma works its way into cracks, between layers, or simply melts its way through surrounding rock, hardening before it makes it to the surface. If the magma cuts across layers of sedimentary rocks (or other types) the formation is called a dike. If the magma forces its way between layers of sedimentary rock, as it did here, the formation is called a sill. The dark sills in the cliffs around the lake (photo below) are associated with a larger formation called the Lost Lake Laccolith, a formation hundreds of feet thick, formed as magma forced its way between layers of sandstone and pooled in a mushroom-shape below the surface.

Click on photo to enlarge.

*The most recent ice age ended about 10,000 years ago. Over the past one million years, Earth has experienced an ice age ABOUT once every 100,000 years.

Terms: channel, laccolith, brackish

This PHOTO ALBUM includes many photos of the Shonking Sag area.

#109 - Montana Tornadoes Were Frequent and Powerful in 2010

Photo Courtesy of Tanja Fransen, National Weather Service

July 26, 2010 . . .
The damage shown in the photo above was caused by the same tornado that killed a 46 year-old man and a 10 year-old boy, injuring the boy's grandmother at the Smith Ranch in northeastern Montana on July 26, 2010. The deadly twister was one of the most powerful ever recorded in the state and the deadliest since 1923, when two men were killed by an F-1 tornado between Missoula and Superior. The tornado that decimated the Smith Ranch had winds that reached 150 miles/hour, making it only the fourth EF-3 tornado ever recorded in Montana, and the first since 1988.

The tornado, which traveled at about 30 miles/hour, was on the ground for 18 miles, demolishing power lines, a bridge and an abandoned house along its path. When it hit the ranch several miles northwest of Medicine Lake, its swath of destruction was .3 miles wide. The twister ripped the house off its foundation and destroyed everything, blowing away grain bins and throwing vehicles over a quarter of a mile. Cattle (both dead and alive) were found more than a mile away, and debris from the ranch was seen 2-3 miles away.

One for the record books . . .
Tornadoes in Montana during 2010 were more numerous and more intense than any season over the past decade. This map from The Billings Gazette, shows how the first 7 months of 2010 compared to previous tornado seasons. Red dots on the map mark the location of the 2010 twisters through the end of July. Although Montana averages only 7 tornadoes per year, there had already been 24 during the first 7 months of 2010.

Why so many?
According to Dan Borsum, senior meteorologist at the National Weather Service Forecast Office in Billings, one possible reason for the high number might have been high humidity levels caused by heavy rains that the region experienced in June. "The amount of moisture that we've had is allowing us to stay in a thunderstorm pattern much later in the year, and that's allowing us to have more intense storms," Borsum said. In more humid parts of the country, tornadoes can form along cold fronts where cool air pushes into hot, humid air. Typically, air in Montana is dry, but 2010 an exception.The 2010 tornadoes were stronger that usual as well. Tornadoes are considered to be strong if they are rated between EF-2 and EF-5 on the Enhanced Fujita Scale. On average Montana gets only one strong tornado per year. But, that number more than tripled in 2010 with the twisters reported in June and July.

Billings tornado . . .
On Fathers' Day 2010 a tornado tore the roof off the Rimrock Auto Arena in Billings (a.k.a. The Metra), which plays host to many of the state's largest spectator events, including basketball tournaments, the state wrestling tournament, rodeos, hockey games, arena football games, concerts, and others. The tornado featured winds up to 120 mph, earning it an EF-2 rating. During the 12 minutes it was on the ground, its swath of destruction was about 120 yards wide and half a mile long. There were no fatalities caused by this tornado.

Term: mesocyclone

#110 - Salinity of Surface Water in Oceans

Click on image to enlarge.

Think "big picture" here . . .
One of the most important "big ideas" in Earth Science is that everything is connected. A great example of this is the long list of factors that influence climate, including the position of continents and mountains (geology), ocean currents (oceanography), changes in the shape of Earth's orbit (astronomy), volcanism (geology), and many more. Astronomy, geology, oceanography, hydrology, and meteorology are are all interconnected in fascinating ways. Even though Montana may be hundreds of miles from the nearest ocean, it is important for everyone to understand some basic principles of physical oceanography in order to understand important Earth systems . . . and be able to look at our planet from a global perspective.

Parts per thousand? . . .
This map (above) uses colors to shows how salinity of surface waters in oceans varies throughout the world. Salinity, which is measure of how much salt is dissolved in the water, is expressed in parts per thousand (ppt). For example, surface waters along the equator between South America and Indonesia have salinities of about 34.6 ppt. This means that 1000 pounds of this salt-water, includes 965.4 pounds of water and 34.6 pounds of salt. Notice that equatorial waters tend to be saltier than those located 30 degrees north and 30 degrees south of the equator. The area along the equator generally gets much more rain than areas 30 degrees to the north or south because of the pattern of atmospheric circulation. The worlds great rain forests are near the equator (the Amazon, etc.), whereas some of the great deserts (the Sahara, etc.) are 30 degrees to the north or south. Observe how salty the Mediterranean Sea is compared to surface waters in the big oceans. The hot, dry climate of that region causes water to evaporate, leaving salts behind.

So what's up with those polar areas? . . .
As you look at the map, notice that surface waters in the polar areas are not as salty as other places, and also observe that surface waters in the Arctic less salty than those around Antarctica. One reason the polar waters are not as salty as those closer to the equator is simply because salt doesn't dissolve as easily in really cold water . . . and this is some REALLY cold water. As for the difference between, the Arctic and Antarctica, it has to do with precipitation and melting. Snowfall, and then the melting of snow and glaciers, which is more prevalent in the Arctic, adds freshwater to the Arctic Ocean. . . This dilutes the salt-water.

Salinity AND temperature affect density . . .
One of the driving forces in oceanic circulation (currents) is variations in densities of waters that originate in different source areas. Salinity is one of the factors that makes water more dense . . . Salty water is heavier than water that is not salty (as long as temperature is constant). A second factor that makes water more dense is temperature. Since the molecules in colder water are moving slower, they tend to be closer together. So if you had a beaker with 100 ml of hot water and one with 100 ml of cold water, the beaker of colder water will be heavier because it actually contains more water molecules. As it turns out the ocean water with the highest density is water that originates near Antarctica. There water can get down to a frigid -1.9 Celsius and have a salinity of 33.8 ppt. This water, which sinks to the ocean floor and moves northward, is appropriately named "Antarctic Bottom Water".

Term: the oceanic conveyor belt

#111 - MSU Paleoecologists Study Ancient Lake Mud

Paleo refers to ancient, and ecology is the study of interactions between organisms and their environment. The goal of paleoecology is to learn about pre-historic ecosystems in a specific region, using clues found in nature. It is related to a broader science called paleoclimatology, which strives to understand past climates and factors that influence them. Research in both areas has increased in recent decades because we've recognized the importance of understanding climate change and how it affects ecosystems. Knowledge gained from this research will help us understand climate change and be more informed as we plan for the future.

One person's mud is another person's treasure . . .
There are several places to find clues about past climates and ecosystems, and many of them involve core sampling, including glacial ice, sea-floor sediment, tree-rings, and coral reefs. Research groups at various universities and institutions throughout the world specialize in the study of each of type of core. At the Montana State University Paleoecology Lab, the focus is on lake-sediment cores that contain mud deposited since the end of the last ice age, over 10,000 years ago. In fact, under the direction of Dr. Cathy Whitlock, the MSU research group is among the world leaders in this area. Whitlock and other scientists at the lab have studied cores from several continents. Since most lakes formed since the last glacial maximum (about 20,000 years ago) lake-sediment research is limited to this part of Earth's history. But, understanding this period is especially important because it witnessed the rise of civilizations, the agricultural revolution, the industrial revolution, and some interesting climate changes.

Why lake mud? . . .
Lakes are basins (low places) where a variety of materials are deposited, and may sit undisturbed for thousands of years. Some of these materials provide clues that help researchers figure out what the ecosystem and climate were like thousands of years ago. For example, cores from the depths of small lake between Missoula and Great Falls represent the top 8.85 meters of sediment, which has been deposited over the past 12,500 years. Besides clay that was transported as wind-blown dust, organic materials, and complex geochemical clues, the mud contains two fairly straight-forward types of evidence related to past climates. Pollen from plants that lived in the area is abundant in the mud can be identified and counted to determine which plant species lived in the area and which ones were most abundant. Knowing this is crucial to understanding the climatic conditions that existed when those sediments settled to the bottom of the lake. Another clue, fragments of charcoal that are embedded in the layers of mud, provides data about the timing and extent of ancient forest fires in the ecosystem. As recent large forest fires in the West have shown, climate, vegetation, and fire are closely related, making ancient charcoal studies an important part of lake-sediment research.

How do they know how old? . . .
It makes no sense to do charcoal and pollen counts unless you can determine the age of the mud at specific depths . . . and there are a couple ways to do this. For one, deposits of tephra (especially ash) from specific volcanoes serve as general markers for dating. Undisturbed lakes in Montana often include a layer of ash from the eruption of Mt. Mazama (Crater Lake) in Oregon ~7,600 years ago, as well as a layer from Glacier Peak in Washington, which erupted ~11,000 years ago. Another, more important way to date the layers, is to use radiocarbon dating (Carbon-14 dating). When larger pieces (at least 1 g.) of charcoal or seeds, etc. are found in mud, they can be sent to labs that specialize in determining their age. Once dates are established for certain layers, researchers can estimate the age of other layers. A small percentage of lake sediments are varved;, i.e. they have distinct layers that formed every year, much like tree-rings. If a core has varves, its simply a matter of counting back in time . . . one layer for each year.

The fun part . . .
One nice thing about research in any area of Earth Science is that it usually involves a field trip, often to a location that has not been too disturbed by human activity. Lake-sediment cores are obtained by pushing a coring device, which consists of a long metal cylinder, several meters into the mud. Coring is done in the deeper part of the lake where the sediment hasn't been disturbed by waves and animals. The process can be accomplished from a boat, but often it is done during the winter when the lake is frozen over.Thick ice provides a strong platform to stand on as the device is pushed the into the mud and then pulled out. Once retrieved, the cores are kept in a refrigerated storage room in the same building as the Paleoecology Lab at MSU. Researchers make many trips to "cold storage" during the span of their project.

Term: proxy evidence

#112 - Lone Peak Rock Glacier at Big Sky, Montana

I thought glaciers were made of ice . . .
If glaciers can be described as rivers of ice, then rock glaciers can be described as rivers of rock and ice. They can be spotted in relatively arid (dry) alpine (mountainous) environments as steep-edged, tongue-shaped, talus-mantled lobes coming off the slopes of valley walls or peaks. Rock glaciers have steep edges because there is ice inside them, holding all the rocks in place at an angle that is steeper than would otherwise be natural for a pile of rocks. This ice inside of rock glaciers can either be a solid core that perhaps was a glacier back before it was buried in rock, or it can be frozen between rocks as a sort of glue that formed as rain water and snow melt ran between rocks and then refroze.

Right: The Lone Peak Rock Glacier located on Big Sky Resort property in southcentral Montana (Aerial photo by Dave Lageson, late 1980s prior to tram construction).

They're everywhere . . .
Rock glaciers have been studied in mountain ranges on almost every continent, and they are especially abundant in southcentral Montana (see map below). They are likely to be found wherever there are steep slopes, cold temperatures in the winter, and a supply of rocky material (known as talus). Scientists think that rock glacier development and persistence is dependent on what size of talus is available, but that hypothesis is still being tested. The hypothesis states that there is a "sweet spot" for talus. Talus covering a rock glacier can act as a blanket that traps cold air and keeps the ice beneath cold. Talus that is too small will not provide enough space between rocks for cold air to flow. Talus that is too large will provide too much space between rocks and so cold air will escape.

Skiing the rock glacier gnar . . .
The Lone Peak rock glacier (LPRG) is located on Big Sky Resort property, directly beneath the bottom lift station of the famed Lone Peak tram. The tram runs to the top of Lone Peak at 11,166 ft (3399 m). See if you can find the tram in this photo. Skiers coming down from "The Big Couloir" and other runs accessible via the tram will ski over a large mound, affectionately known to locals as "the Cueball." The Cueball is actually a rock glacier that is probably thousands of years old. Samples of ice were taken from the LPRG in the summer of 2009. The ice at LPRG is inside the rock glacier, though, so sampling involved excavation of ~3 m (~ 9 ft) of talus and use of a mini-Bobcat excavator. Once removed it became clear that this thick blanket of rock was doing its job; a continuous layer of ice was encountered at a depth of ~ 3 m. The layer of ice was then sampled using a chainsaw. Ice blocks ~ 20 cm x 20 cm were recovered. Under the layer of ice was a layer of ice and rock frozen together. The insides of a rock glacier are complicated and do not consist of only one material (ice) or another (rock).

Wrinkling like a rug . . .
Just like glaciers, rock glaciers move! Most rock glaciers have average surface velocities of a few tens of centimeters per year. The LPRG is no exception. Since the bottom lift station of the tram was built on the rock glacier in 1995, its movement has been closely monitored. As they flow downhill, many rock glaciers exhibit a wrinkly surface that looks like a rug that has been crumpled. These wrinkles are technically referred to as ridge and trough topography, and seem to be related to the movement of the rock glacier. It is thought that the wrinkles represent faults within the rock glacier. In other words, as the rock glacier moves downhill it gets caught up on itself. Just like tiles overlapping on a roof, or wrinkles on a rug, segments of the rock glacier start to overlap each other.

Life in the ice . . .
Geoscientists have taken ice samples from the bottom of glaciers in Antarctica and the Canadian Yukon and studied them for their microbiological content. These ice samples tend to be pretty dirty; that is, they contain a lot of particulate rock debris. The results of these studies show that microbes are associated with debris; that is they prefer to hang out in ice that has rock particles in it rather than ice that is clean, i.e. no rock particles are present. Certain microbes can use rock debris as food; their metabolic processes depend merely on having a carbon source and an electron acceptor available. Microbes can use rock debris to serve these purposes and are quite happy in an environment as seemingly unfriendly as the bottom of a glacier where it can be very dark and very cold. According to these findings, it seemed to follow that rock glaciers would be happy environments for microbes that can live in icy environments where rock debris is present. Microbiological experiments performed on ice samples taken from the LPRG show that indeed, microbes are present in higher concentrations in ice samples with particulate rock debris.

Term: talus

Thanks to Caitlyn Florentine for contributing the content (images and explanations) on this page!

#118 - Thin-Skinned Thrusts Along The Rocky Mountain Front

Photo taken by Bobak Ha'Eri, on June 3, 2009 (Wikipedia).

The "front" of what? . . .
This aerial photo, which was taken 65 miles west of Great Falls, shows the Rocky Mountain Front; one of Montana's most treasured areas. The Front is the eastern edge of the Rockies and the adjacent prairie, extending from the Simms area northward through Browning into Canada. In other parts of Montana, the transition from mountains to prairie is much more gradual, so perhaps the name comes from the fact that travelers heading west across the prairie could see the abrupt "front" of these mountains from many miles away. The Front, which is valued for its beautiful ranches, incredible scenery, and outdoor opportunities, is also recognized as one of the nation's most important wildlife areas. Grizzly bears still wander down onto the plains in the spring and almost all other pre-settlement plants and animals (except the bison) are still present. Migratory waterfowl use the abundant wetlands found along The Front, and the diverse mix of habitats supports many species.

There's been a disturbance . . .
The ridges in the photo are layers of Madison limestone, made of sediment deposited on the floor of a shallow ocean over 300 million years ago (map). Like many mountains throughout the world, visitors to this range can find fossils of ancient sea creatures thousands of feet above sea level. The presence of mountains and the fossils they contain prove that this part of the Earth's crust was disturbed (a.k.a. "messed up", deformed). Quite often such disturbances involve crustal plates colliding - and that was definitely the case here. From about 80 to 40 million years ago, the Pacific Plate was slowly pushing into the North American plate many miles to the west of Montana (map), inching layers of rock upward and causing scattered areas of volcanism from Mexico to northern Canada. This collision gave rise to the Rocky Mountains. Layers formed on ancient ocean floors were uplifted, folded, faulted, or tilted . . . or all of the above. It can get messy! But these geological messes are the mountains we have today. In contrast, layers beneath the soils of eastern Montana were disturbed very little, so that part of the state is fairly flat.

Like shingles on a roof . . .
For obvious reasons the part of the Rockies shown in the photo was named the "Sawtooth Range". The Sawtooths and other mountains along The Front are associated with of one of Montana's most famous geologic features . . . It's called the "Lewis Thrust Belt", and ever since it was discovered it in the early 1900s, it has been considered one of the world's classic geologic structures. In this thrust belt, fractures formed in sedimentary rock formations and then rock layers on west side of the fault(s) slid up and over layers to the east. Huge slabs of sedimentary rock slid eastward as far as 50 miles, slowly pushed by the same collision that caused the faults. These slabs sit where Glacier Park and the Great Bear, Bob Marshall, and Scapegoat Wilderness Areas are today. However, in the Sawtooth Range the thrust-faulting happened a little differently (see diagram). The slabs that slid up and over were thinner, and there were more faults than were formed to the north and west. Before the thrust-faulting, the fragmented pink areas on the diagram were once a single, continuous, horizontal layer. The long, north-south ridges in the photo above are the upturned edges of these thinner slabs of Madison limestone that slid eastward and onto younger rock layers like the shingles on a roof. (Diagram courtesy of Montana Bureau of Mines and Geology Publication: "Profiles of Montana Geology")

What goes up . . .
Ever since these mountains started forming, weathering and erosion have been working to wear them down. Rivers from the Continental Divide to the west carved outlets through the thrust-faulted layers, transporting water and sediment to the Missouri River. The Sun River, which joins the Missouri near Great Falls, can be seen in the photo at the top of this page. Gibson Reservoir (also in top photo) on the Sun River stores spring run-off that is used throughout the summer to irrigate farmland between here and Great Falls.

Term: thrust fault

#119 - Bakken Oil Fields Visible from Space

Click on image to enlarge

Room with a view . . .
This photo was taken from the International Space Station as it orbited over Montana on Ocober 11, 2011 (north is to the left). Towns like Glasgow and Havre appear brighter than normal and and look like dashes, rather than dots, because the astronaut used a 1-second exposure. You can see Ft. Peck Reservoir and several unlabelled communities - Chinook, Harlem, Ft. Belknap, Malta, Lewistown, and others. The cluster of lights in the Williston area of North Dakota is oil wells where natural gas is being burned off as waste. Unfortunately, the gas can't be hauled off in trucks and there are few pipelines in this area, so about a third of it is burned off, or "flared" (photo). Failure to do controlled burns would endanger workers and nearby residents, and venting to the atmosphere would greatly increase the release of greenhouse gases. (Source: National Geographic Magazine) Side Note: The green arc on the horizon is the ionosphere, which is not visible with the naked eye.

New technology causes a boom . . .
The lights on the photo also mark the approximate location of the Bakken formation, which is made of sedimentary rock layers deposited in a marine environment during the late Devonian (map) and early Mississippian Periods. The formation, which is about two miles below the surface, is named after Henry Bakken, a farmer in North Dakota who owned the land where it was discovered. Although oil and gas were discovered in the Bakken in the early 1950s, the low the permeability of the rock made it difficult to remove them. Only recently (2008) have advances in horizontal drilling and hydraulic fracturing (fracking) finally made it possible to remove the oil. According to the government's Energy Information Administration, oil production here went from 3,000 barrels a day in 2005 to 225,000 in 2010, pushing North Dakota to the #2 spot among oil-producing states, second only to Texas. To learn much more about the Bakken Oil Boom (graphs, diagrams, videos), go to Geology.com.

Layers, formations, basins? . . .
The Bakken formation is part of the Williston Basin, which was a low area throughout much of Earth's history where layers and layers of sediment were deposited. Although this region is not a low area today, the total thickness of the sedimentary layers that filled the basin is over 3 miles in some places, and many of the layers are known for rich deposits of oil and gas . . . especially the "Bakken shale". The Bakken Formation, which is about 2 miles deep, actually consists of three "members" - a lower shale, a middle sandstone, and an upper shale. The Bakken is about 150 feet thick, and lies directly beneath the Madison limestone, a formation that can be seen at the surface in many places throughout central and western Montana. The oil and gas formed within the two shales, but all three parts of the Bakken yield these resources. (Map Courtesy of www.bakkenresourcesinc.com)

The Mush . . .
Contrary to popular belief oil and gas are NOT formed from the fossil remains of dinosaurs. Actually, most oil and gas originate from the remains of microscopic marine plants and animals called "plankton". As plankton dies it settles to the sea floor where it forms an organic mush. This was happening in the Williston Basin during the Late Devonian and Early Mississippian Periods. Usually there are plenty of critters (especially worms) living on the sea floor that consume this mush. However, at certain times in Earth's past there have been places where the deep water contained no oxygen (anoxia). This can happen when deep water becomes stagnant and doesn't mix with the oxygen-rich surface water. Animal life can't survive where the deep water is completely lacking oxygen, and without animals to eat the dead plankton, the organic mush builds up on the sea floor. Where ocean sediment contains more than 5% organic material it eventually forms a rock known as "black shale". The color comes from the dark organic matter that it contains. The Bakken Shale(s) formed this way.

The Big Squeeze . . .
As more sediment accumulates, the Bakken Shale became buried more deeply, and slowly began to heat up. Eventually this heating causes organic material in the plankton to undergo chemical and physical changes. At temperatures of around 30 C, a solid, sticky bitumen is produced. Then at 90 liquid oil is formed. As temperatures reach 150 C, natural gases like methane are given off. Usually the hot oil and gas does not stay in its "source rock" for long. These hydrocarbons are less dense than the water in the rocks that surround them, so they gradually migrate upwards through the pores between the particles that make up the rock or they may find their way up through cracks, fissures, and faults in the overlying rocks. Eventually oil and gas get trapped in pockets (reservoirs) beneath impermeable layers of rock. However, this is not what happened with the Bakken Shale.

Technology Team-Mates . . .
The Bakken shale has a very low amount of pore space and it is very difficult for liquids to move through it (low permeability) - much lower than typical oil reservoirs. So, even if companies drilled into the shale the oil did not come out. However in 2004 the price of oil climbed above $40 per barrel, motivating producers to develop new ways to extract this oil. As a result two new technologies have finally made it possible to remove oil and gas from the Bakken. The presence of natural vertical fractures makes the Bakken an excellent candidate for new drilling techniques in which a well is drilled horizontally along bedding planes, allowing it to tap many thousands of feet of reservoir rock. Production can also be enhanced by new ways to artificially fracture the rock (fracking), which allow oil to leave the shale and seep to the well.

Term: fracking

#120 - Lake Helena Watershed

It's all downhill from here . . .
For a drop of water (rain or melted snow) on a mountain slope there are three options - evaporate, soak into the ground, or flow downhill. A drop that flows becomes "runoff", and will soon join with other drops to form a trickle and eventually a small stream. Any runoff within the yellow line shown on the map eventually ends up in one of the larger streams (blue lines) that channel water to Lake Helena. From there runoff flows into the Missouri River, onto the Mississippi, and finally into the Gulf of Mexico.

a.k.a. Drainage Basin . . .
The outlined area on the map is called the Lake Helena Watershed (larger version of map). It includes the Helena Valley and the surrounding mountains where the water comes from - mostly from melting snow. A watershed is all the land whose runoff flows into a particular river or body of water. The watershed of the Mississippi (a.k.a. the Mississippi Basin) includes 41% of the lower 48 states. If you live in Helena, you live in the Lake Helena Watershed and you are also part of the Missouri River Basin and the even larger Mississippi Basin. In fact most of Montana is part of the Mississippi Basin. But no matter where you live, you are in a watershed and human activities in that watershed may impact the quality of water available to you.

Water for the Capital City . . .<
Wells (groundwater) are the source of water for many who live in the Helena area, including East Helena, Montana City, various subdivisions, and those not connected community systems. However, the primary source of water for the 30,000 who live within the city of Helena is surface water. Although the city does use some groundwater, most comes from two surface water treatment plants. The Missouri River Treatment plant, located in the Helena Valley, treats water that has been pumped from Canyon Ferry. Helena's main source of water is the upper portion of the Tenmile Creek Watershed. ("upper" means higher, or closer to the headwaters.) The Tenmile Water Treatment Plant, located 10 miles west of Helena, provides most of Helena's water.

Get it while you can . . .
Since most of the runoff from the 42 square mile Upper Tenmile Watershed flows down from the mountains during spring and summer, the City of Helena devised a way to collect that abundance and store it for use throughout the rest of the year. Water from streams in the upper part of the watershed is stored in Scott and Chessman Reservoirs. Chessman Reservoir is filled by water from Banner Creek - a tributary of Tenmile Creek. Water diverted from Banner travels through the 5-mile long Red Mountain Flume to Chessman Reservoir. From there it can be released as needed (mostly in winter) into another stream that takes to the Tenmile Plant. The plant cleans up the water, adds chlorine, and then pipes it into town where it is stored in tanks - ready for use.

A troubled past . . .
Most watersheds have issues and the Upper Tenmile Watershed has more than its share. In 1999, the EPA added the area to the Superfund National Priorities List due to problems caused by waste rock and tailings at abandoned mines that produced gold, lead, zinc and copper from 1870 through the 1920s. Waste rock and tailings piled near these sites can cause acid mine drainage which taints runoff with dissolved metals. The EPA identified 150 individual mine sites within the watershed . . . 70 have been prioritized for cleanup and some of these are above Scott and Chessman Reservoirs. Despite this problem, the Upper Tenmile Watershed continues to provide high quality water for the city of Helena.

Term: tailings

To see photos of the Red Mountain Flume CLICK HERE.

#121 - Nice (Gneiss) Basement Rock

First things first . . . This outcropping is located in a cirque called Beehive Basin about 35 miles SSW of Bozeman, Montana. An outcropping is a place where Earth's crust (bedrock) is exposed (not loose rock and not covered with soil, etc.) - usually a steep area. A cirque is a U-shaped mountain valleys carved by an alpine glacier. Point C on this aerial photo marks the location of the outcropping. Once the page opens, zoom out to see the entire valley, and beyond to get a sense of where this place is.

What's so nice about it? . . . The rock shown in the photo above is a type of metamorphic rock called gneiss (pronounced "nice"). Metamorphic rocks are formed when sedimentary or igneous rock is changed by heat and/or pressure (and in some cases, chemically active fluids). Gneiss can form from several different types of parent rocks, including granite, shale, or volcanic rocks, although most textbooks feature gneiss that was formed from granite. Other common metamorphic rocks include marble (used to be limestone), quartzite (used to be sandstone), and slate (used to be shale).

Not just for butterflies . . . Most metamorphism happens in one of two geologic settings. In one, heat from magma beneath the surface may "bake" (but not melt) rock, causing minerals in the rock to recrystallize or even form new minerals. In the other scenario pressure put on rock buried deep beneath the surface or rock near a colliding plate boundary can also cause metamorphism. The slow collision of tectonic plates squeezes large rock formations, causing them to become deformed and metamorphosed. The Rocky Mountains formed from this type of slow collision between 80 and 40 million years ago.

Old stuff in the basement . . . Gneiss makes up most of the lower portion of Earth's continental crust - very old material referred to as "basement rock". In most places basement rock is covered with younger sedimentary rocks. Drill down far enough anywhere on a continent - you will usually strike gneiss. In fact the rock that makes up the mountains in southern Montana, including the gneiss in the photo, are among the oldest in the state - formed during the Archean (Archeozoic) Eon over 2.5 billion years ago. Here, sections of crust were forced upward and many of the younger rock formations eroded away, exposing the basement rock. Today this gneiss makes up many of the mountains in the region, including the Beartooths, the Tobacco Roots, and a significant portion of the mountains in between.

Term: contact metamorphism, regional metamorphism (in your own words!)

#123 - Moraine of the Grinnell Glacier

This is as far as we go.

Grinnell Glacier Moraine . . . This photo, taken near Grinnell Glacier shows a ridge of rock material (till) known as an "end moraine". The moraine consists of rocks of various sizes (unsorted), ranging from silt to boulders - an obvious sign that they were deposited by a glacier. Rocks that were stuck to the bottom of the Grinnell Glacier (or had fallen onto it, etc.) were carried here by the glacier and then dropped as the ice melted at the terminus of the glacier. A significant moraine such as this indicates that the climate must have been stable for several decades, causing the terminus of the glacier to be stationary. If it had been advancing due to a cooling climate, or receding due to warming, the rock material would not have built up as it did here. The span of stable climate that allowed this moraine to form happened during the Little Ice Age, a cold period that lasted for centuries, ending in the mid-1800s. Since then the Grinnell Glacier has been receding due to the warming climate, causing the glacier to melt away from its moraine.

Not the first time the glaciers have melted away . . . Contrary to popular belief, the glaciers in Glacier Park are NOT "leftovers" from the last ice age, which ended roughly 10,000 years ago. There is little doubt that ice age glaciers WERE responsible for carving the majestic peaks and valleys of the park (horns, cirques, aretes, hanging valleys, etc.), however experts believe those glaciers completely melted away during a warm period 9,000 to 5,000 years ago (known as the altithermal or Holocene Climate Maximum). On the other hand, glaciers present in the park today formed during the Little Ice Age (not a true "ice age") - a centuries long cold period that ended about 150 years ago. According to evidence from moraines, tree rings, layers of volcanic ash, and radiometric dating, these "Little Ice Age" glaciers formed in cirques that were carved by glaciers during the last real ice age(s). The photo at the top of this page shows the end moraine that marks the farthest advance of the Grinnell Glacier during the Little Ice Age. The photo below shows that same moraine as viewed from Mt. Gould.

What if he had gone along? . . . Grinnell Glacier is named after George Bird Grinnell (1849-1938), an American anthropologist, historian, naturalist, and writer. Grinnell was born in New York, and graduated from Yale University with a B.A. in 1870 and a Ph.D. in 1880. As a graduate student, he accompanied Lieutenant Colonel George Armstrong Custer's 1874 Black Hills expedition as a naturalist. Fortunately he passed on a similar opportunity to accompany Custer on the 1876 expedition - All the participants on that trip died at the Battle of the Little Big Horn in June of 1876. Instead, Grinnell lived a long and influential life, which included playing a major role in establishing Glacier Park. After exploring the area in 1885, he was instrumental in getting it designated as a national park in 1910. Who knows? If Grinnell had gone with Custer, the area may have never become a national park.

Above: Lisa McKeon and Lindsey Bengtson photograph Grinnell Glacier from the summit of Mount Gould in August of 2009. Courtesy of the USGS

Term: glacial till