#11 - The Cliffs of Crown Butte

Click on photo to enlarge.

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

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

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

Terms: laccolith, intrusive formation

#2 - Classic Squall Line of July 8, 2002

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

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

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

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

Term: cold front

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

#3 - Watershed of the Yellowstone River

Runoff . . .
This image shows all the area that sends runoff into the Yellowstone River. This land is referred to as the Yellowstone River's "watershed", "drainage basin", or just "basin". Any rain or snow within the watershed that does not evaporate or soak into the ground will eventually end up in the Yellowstone River. Unfortunately, chemicals (fertilizers, herbicides, etc.) can also be carried into the river with the runoff. The primary source of water for the Yellowstone River is winter snow that falls in mountains within the basin during the winter. The flow of water (a.k.a. "discharge") in the Yellowstone is usually greatest in June when the snow in the mountains is melting rapidly.

Getting started . . .
As you might expect, the "headwaters" (starting point) of the Yellowstone River are in Yellowstone Park. The river flows northward out of the Park to Livingston. There it turns to the east, flowing toward North Dakota. The Yellowstone's larger tributaries are also shown on the map, and each of these has its own watershed. A large portion of the Bighorn and Powder River watersheds are located in north-central Wyoming.

Montana's Big Three . . .
The western third of the Montana drains into the Clark Fork River, and most of northern Montana empties into the Missouri River. Since the Yellowstone joins the larger Missouri River in North Dakota, the Yellowstone's watershed is considered to be part of the Missouri's watershed. Since the Missouri joins the Mississippi near St. Louis, its watershed is part of the Mississippi's. Unless it evaporates or is removed for use by cities or farmers, runoff from the Yellowstone River's watershed will end up in the Gulf of Mexico.

Terms: runoff, tributary

#4 - Triple Divide Peak in Glacier Park

Click on photo to enlarge.

Like the Matterhorn . . .
The peaks shown in the photo are glacial horns located in Glacier National Park. These pyramid-shaped features are formed as three or more glaciers erode the sides of a single mountain. The larger peak in the background is Mt. Stimson and the smaller horn in the center is called Triple Divide Peak. Triple Divide Peak was so-named because runoff from each of its three sides drains to a different watershed. (Runoff is melted snow or other forms of precipitation that drain off the land.) Melted snow from the west slope (left side) flows toward the Gulf of Mexico, runoff from the northeast slope (right) flows toward the Hudson Bay, and the southwest slope (behind the peak) drains to the Pacific.

Dividing lines . . .
The photo at the top of this page was taken near a ridge separates the Gulf of Mexico and the Hudson Bay watersheds (drainage basins). Such areas are known as "divides". Divides are higher areas (not always distinct ridges) that separate drainage basins. The most famous divide, The Continental Divide (a.k.a. the Great Divide), is also shown in the photo. The map on the right shows the divides that separate our continent's drainage basins (watersheds). Triple Divide Peak is labelled. Click on the map to enlarge it.

More about Triple Divide Peak . . .
CLICK HERE for an account of two hikes to the summit of Triple Divide Peak (including a linK to a photo tour).

Below: That's me walking along the Continental Divide between the Hudson Bay and Pacific Ocean watersheds on my way to the summit of Triple Divide Peak.

Terms: (drainage) divide, watershed

#5 - Ocean Front Property in Montana

Map Courtesy of Chris Scotese, PALEOMAP Project www.scotese.com; click on image to enlarge

When dinosaurs roamed . . .
During much of the Cretaceous Period (144 to 65 million years ago) a large portion of Montana was covered by the waters of a shallow, inland sea called the Western Interior Seaway. The sea was formed as west-central North America was subsiding to an elevation below sea level. As this sinking occurred the area filled with water from the Gulf of Mexico and the Arctic Ocean.

Source of the sediment . .
Between 80 and 40 million years ago, tectonic forces were building the Rocky Mountains in western Montana and Idaho. Rivers flowing eastward from these mountains transported massive amounts of sediment (sand, silt, clay) to this sea. As the land cycled between periods of uplift and subsidence, the seaway expanded or shrank, resulting in dramatic east-west shifts in the location of the coastline. CLICK HERE to watch a video of the fluctuating Western Interior Seaway.

Where do I drop you off? . .
Changes in the location of the coastline also caused changes in the type of sediment deposited in different areas. . . Sand was deposited closer to the coast, whereas silts and clays settled to the bottom in deeper waters. Watch this animation. As layers of sand, silt and clay became buried, they were compressed and turned into the sedimentary rocks found today in central and eastern Montana, and throughout the rest of the west-central United States. For example, the "Rimrocks" of Billings are made of sand deposited at or near the shoreline of the ancient Western Interior Seaway.

Terms: subsidence, deposition

#9 - A Meteor Among Circumpolar Star Trails

Circumpolar . . .
Robin Loznak took this photo for tThe Daily Interlake from the summit of Big Mountain near Whitefish. She pointed her camera at Polaris (The North Star), and then left the shutter open for 70 minutes, recording the motion of stars in the northern part of the sky. Such motion is referred to as "apparent" because it is not caused by the movement of the stars, but rather the spin of the Earth on its axis. It's like being on a merry-go-round and thinking that your surroundings are moving. The Sun and Moon move across our for the same reason. Since Polaris is directly above the North Pole, it stays put while the other stars seem to circle around it - They're referred to as circumpolar stars.

A rock among stars . . .
The straight bright line is a meteor (a.k.a. "shooting star"). Meteors are not stars at all. Instead they are small rocks that burn up in our atmosphere as they are pulled in from space by our planet's gravity. On any night, at any location, a few meteors can be seen each hour. Occasionally, intense meteor displays fill the sky with tens, hundreds, or even thousands of meteor trails. These displays, called meteor showers, can be predicted because they repeat every year when Earth passes through an area where a comet has passed through. The bits of debris left behind by the comets, most no larger than a grain of sand, create a spectacular light show as they enter the earth's atmosphere. The meteor in this week's photo was part of the Perseid Shower that occurs every year around August 12-13 as a result of debris left behind by Comet Swift-Tuttle.

Term: circumpolar stars, meteoroid

#13 - East Helena Superfund Site

The three photos on this page show the yard replacement program that took place in East Helena to remove soils that had been contaminated with lead (also arsenic and cadmium).

Mistakes of the past . . .
For more than 100 years emissions from the ASARCO Lead Smelter caused lead to be deposited in the soils of East Helena. Microscopic lead particles were released from the tall stacks that stood on the smelter property until 2009. At the smelter, which closed in the late 1990s, tall stacks were used to put the pollution higher into the atmosphere where winds would carry it away and spread it out more. Unfortunately, a significant amount of lead ended up falling in the community of East Helena where it became part of the soil. As children played they may have inhaled some of the dust (including lead particles). Some of the lead would dissolve in the moisture in their lungs where it would be absorbed into their blood.

On the list . . .
In 1984 East Helena was added to the EPA's (Environmental Protection Agency) Superfund Priorities List. Superfund sites are places that must be cleaned up because they pose a risk to human health and/or the environment.

Lead in the bodies of children . . .
Testing in 1975 indicated that children in East Helena had elevated levels of lead in their blood as result of inhaling dust from lead-contaminated soils. During the clean-up, which took place mostly in the 1990s, soil from over 700 yards was replaced. The soil replacement program continued to take place as children moved into houses where soils were contaminated.

Top photo: First, the soil was removed to a depth of about 6 inches.

Middle Photo: New topsoil was brought in.

Bottom photo: Finally, sod was placed on top of the new soil.

CLICK HERE to Watch the stacks come down. (YouTube Video 2:51)

Terms: Superfund Site, smelting