Montana Lake Carved by Outburst Floods During Ice Age

Lots of geology going on here. Two of my hiking buddies are standing on the remains of a laccolith looking at Lost Lake whose basin was carved by outburst floods during the last ice age. The mountains in the background (Highwoods) are the remains of an ancient volcano that was active 50 mya.

After visiting Lost Lake we hiked up onto Square Butte (another laccolith). Both features are made of rock formed as magma cooled beneath the surface tens of millions of years ago. However, the story of Lost Lake includes another chapter that involved an unusual set of circumstances that happened during the last ice age. To learn how outburst flooding of Glacial Lake Great Falls was involved, go to bigskywalker.com.

GREAT 13-minute segment about Mars from "60 Minutes"

In case you missed it, this is a GREAT segment that includes several important Earth Science concepts - Earth's magnetic field, plate tectonics, law of superposition, erosion, meteorites, etc. Consider showing it as you teach about the rock cycle. Here are some possible questions to guide a discussion after showing it.

1. Is there a "rock cycle" on Mars?
2. How is it different from the rock cycle on Earth? What processes are missing?
3. Is there molten rock on Mars?
4. Are there metamorphic rocks on Mars?
5. What drives the rock cycle on Earth?

Convection - The straw that stirs the drink.

Whether you're talking atmosphere, oceans, or mantle, one of the most important processes in Earth systems is convection. Here is one of our favorite activities for our freshmen Earth Science students at Helena High. The lab, which has two parts, allows students to see convection as it happens. The part shown in the video below focuses on helping students understand the role convection plays in causing wind. The box of water represents air.

The lab comes in a kit we purchase from WARD'S Natural Science, which includes this 2-part activity plus another activity related to ocean currents. The kit is called "Exploring Convection." To make the blue ice cubes, add 3 drops of food coloring to each empty cube mold in an ice cube tray, add water, and freeze.

CLICK HERE to see a video of "Part I".

CLICK HERE to see a video of the other lab included in the kit (related to ocean currents).

How the USA Generates Electricity

Check out this interesting Washington Post site, which includes several informative graphics. Every student should have some sense of where electricity comes from? Once the site opens, be sure to scroll down and select the different types of energy to see how each state generates electricity - Just below where it says, "Click to rearrange."

Glacial Striations on Snake Butte

Click on the image to see a larger view.

This photo, taken on Snake Butte in north-central Montana, shows scratches that were made as the Laurentide Ice Sheet (continental glacier) flowed across here during the last ice age. Rocks that were stuck to the bottom of the ice caused the gouges - called "striations." Snake Butte is about 10 miles south of Harlem, MT on the Ft. Belknap Indian Reservation. The Little Rockies can be seen in the distance.

Striations help determine which direction the glacier flowed as it grew across the land, and also help locate "spreading centers" where the ice grew FROM, before merging to form the single continental glacier that covered Canada. Striations found in various parts of Canada reveal that there were three places in northern Canada where snowfall accumulations contributed to the ice sheet that eventually reached the USA (Of course there was no USA at that time!). These striations on Snake Butte prove the glacier flowed toward the southeast as it moved over the butte - probably because the Bears Paw Mountains (several miles southwest of here) forced the ice in that direction.

Below: The black dashed line indicates how far south the ice advanced into Montana when the ice age peaked about 18,000 years ago.

In addition to striations, the Laurentide Ice Sheet left other clues in the Snake Butte area.

1. Erratics – Metamorphic rocks from the Hudson Bay area can be found on Snake Butte (and throughout northern Montana). These rocks, which were embedded in the ice, were dropped here when the ice melted.

2. The Snake Butte Boulder Train – Large pieces of Snake Butte (igneous rock) have been scattered in a straight line extending to the southeast of Snake Butte. As the glacier flowed across the butte, pieces of the butte were carried away, and eventually dropped as the ice melted. Although they are few and far between, the line extends for almost 50 miles. The direction of the boulder train matches the direction indicated by the striations.

For much more about Snake Butte, CLICK HERE (includes a photo tour).

Concretions Along the White Cliffs of the Missouri River

There are several places in and along the White Cliffs of the Missouri River in north-central Montana where you can see great examples of concretions. A concretion is a roughly spherical mass of sandstone embedded in less durable sandstone. Concretions form within layers of sand/sandstone that have already been deposited, usually before the rest of the sand has hardened into rock. Concretions form when a mineral precipitates and cements sediment around some sort of "nucleus", which is often organic - a leaf, tooth, piece of shell or fossil. Fossil collectors sometimes break open concretions in their search for fossil animal and plant specimens. The "concretionary cement" often makes the concretion harder and more resistant to weathering than the sandstone it is embedded in.

Below: Here are a couple more photos of concretions along the White Cliffs of the Missouri. This 47-mile stretch is one of the premier canoe/kayak trips in the USA. CLICK HERE for an account of the 3-day journey (lots of photos). Here is another link to more information about concretions, including a short video (does not open on many mobile devices).

Strange Fossils in Glacier Park

These are fossils of stromatolites that can be seen along one of the most popular trails in Glacier Park. CLICK HERE to see more photos taken along the Highline Trail.

Glacier Park is made almost entirely of rocks from the Belt Formation (aka "The Belt Supergroup") - layer upon layer of sandstones, shales, and carbonates from the late Precambrian Era. At that time there were no organisms with bones or shells, so stromatolites like those shown in the photo, are the only fossils that can be found in Glacier Park.

Stromatolites are mound-like, multi-layered colonies of algae (blue-green algae; aka cyanobacteria), and their formation has much to do with the way they change the chemistry of the shallow water they live in. The photosynthetic cyanobacteria remove carbon dioxide from the surrounding water, causing calcium carbonate to precipitate onto their slimy, mat-like colonies. Calcium carbonate, along with grains of sediment (silt, etc.), stick to the bio-film layer that covers the colonies. As the cyanobacteria continue to grow up through the sediment, a new layer forms. This process occurs over and over again, creating layered mounds, columns, or sheets.

Fossils of different species of stromatolites can be found in different areas of the park. Stromatolites that lived in the Precambrian played a major role in increasing the amount of oxygen in the atmosphere of the primeval Earth ("The Great Oxygenation Event"). Living stromatolites can be found today at Shark Bay in western Australia.

Check out my Montana Hiking Blog - lots of geology!

Source: T.N. & E.L. Taylor. 1993. The Biology and Evolution of Fossil Plants. Prentice Hall, New Jersey.