Topic:
River Geology
INTRODUCTION
Ranger Abby introduces you to river geology!
I WONDER...
- How was St. Anthony Falls created by nature?
- How do waterfalls move?
- How and why did people change the falls?
VOCABULARY
Click the drop-down list to know your RIVER GEOLOGY words!
Erosion - the slow wearing away of rocks or soil by natural processes, such as rain, wind, ice and snow
Fossil - the hardened remains or imprints of plants or animals preserved in stone or other material
Geology - the study of the origin, history and structure of the earth
Glacier - a large mass of slowly moving ice
Limestone - a sedimentary rock consisting chiefly of calcium carbonate, often containing marine fossils
Sandstone - a sedimentary rock made mostly of sand-like quartz grains, often cemented in calcite or silica
Sedimentary Rock - a rock that is formed when deposits of loose materials are cemented together, usually by lime or silica, to form layers
Shale - a sedimentary rock composed primarily of fine-grained materials such as silt and clay; also called mudstone
Strata - layers of rock
LEARN IT
Understand what makes geology so amazing along this stretch of the Mississippi!
SLIDE DECK: Geology and the Twin Cities
Learn how rocks helped shape the ground you stand on!
VIDEO: A Waterfall on the Move - The Extraordinary Journey of St. Anthony Falls
Learn how St. Anthony Falls in Minneapolis moved to its current location from St. Paul!
READING: Minnesota's Rocky Roots
Learn how different types of rocks, continents, and glaciers are formed, and how the geological history of the earth has been divided into different eras and periods
Click on picture
Teachers - see Resources section for Teacher Guide
READING: Ask a Rock
Learn about the different rocks you can find in Minnesota and how and when they were formed
Click on picture
Teachers - see Resources section for Teacher Guide
DO IT
Get rocking with geology!
ACTIVITY: Create Your Own Strata
Use materials found around the house to see how water can sort sediment. Will they become rocks just like they did millions of years ago? Only time will tell!
KNOW IT
Show what you know about geology with this quick self-assessment!
Choose the best answer to each question, then click its drop-down menu to see the correct answer.
Multiple Choice: What is geology?
A. The study of the physical features of the earth, its atmosphere, and of human activity
B. When you hunt for geodes
C. The study of the origin, history and structure of the earth
D. Looking for dinosaur bones
Answer: C
That was a tough one to start us off! Geo- means "earth" and -logy means "the study of". If you guessed A, it's similar but don't be fooled, that's part of the definition of geography!
Multiple Choice: What are the three types of rocks that can be found in Minnesota named in the article, Rocky Roots?
A. Gneiss, Granite, and Basalt
B. Lava, Slate, and Sandstone
C. Soft, Medium, and Hard
D. Metamorphic, Igneous, and Sedimentary
Answer: D
When lava hardens it forms igneous rock. Metamorphic rocks form when igneous and sedimentary rocks are heated up or squeezed together. Sedimentary rocks form when sand, mud, or other sediments pile up and harden.
Multiple Choice: How long ago was North America covered by an inland sea?
A. 450-500 million years ago
B. In the olden days
C. A Gazillion years ago
D. 12,000 years ago
Answer: A
The period of time is known as the Ordovician Period and it was hundreds of millions of years before the dinosaurs!
Multiple Choice: How long ago did the waterfall start eroding and moving upriver on the Mississippi?
A. Just last year
B. 12,000 years ago
C. 450-500 million years ago
D. What? Waterfalls don't move!
Answer: B
At a speed of 7 feet per year, the waterfall made it's way upriver over 15 miles! You can still see it today in its current location in downtown Minneapolis.
Multiple Choice: Which rock is most likely to erode?
A. Limestone
B. Shale
C. Sandstone
D. Bedrock
Answer: C
You're not going to use it as a pillow at night, but geologically speaking, sandstone is one soft rock. You can use your fingernail to scrape it and pieces of sediment will fall off!
Multiple Choice: The skeleton of a now-extinct species related to a familiar Mississippi River animal was found when layers of eroded shale and limestone were cleared to create a park. What animal was it?
A. Giant Otter
B. Giant Mammoth
C. Giant Crinoid
D. Giant Beaver
Answer: D
The beavers we know today can get up to 3 feet tall but a giant beaver was probably between 6 and 8 feet tall!!
True or False: Minnehaha Falls was created using the same natural building blocks and erosion process as the one on the Mississippi River?
A. True
B. False
Answer: True
Minnehaha Falls is a good example of what the river falls would have looked like before humans modified it. If you have a chance to visit Minnehaha Falls Regional Park, you can see the three layers of rock behind the falls and evidence of erosion at work!
Multiple Choice: What was something they made in the mills of Minneapolis using only the waterpower from St. Anthony Falls?
A. Lumber (by cutting logs in sawmills)
B. Flour (by grinding wheat in flour mills)
C. All of the above
D. None of the above
Answer: C
You can accomplish a lot with the power of falling water! Mills were some of the first buildings in Minneapolis and they brought people to the city from all over the country and the city grew up around the falls.
Multiple Choice: Why did steamboats coming up the Mississippi river have to stop in the spot in the river that is now the capital city of St. Paul?
A. They ran out of fuel
B. There were large chunks of shale and limestone in the riverbed left over from the erosion of the waterfall
C. The river was too shallow
D. The river pirates would get them if they went any farther
Answer: B
As the waterfall eroded it left large pieces of shale and limestone the size of cars in the river bed. These rocks created a hazardous river for large boats and St. Paul became a bustling port city as the last stop on the Mississippi River heading North in a boat, and the place to board a boat heading South.
Multiple Choice: Why did humans put cement over the natural waterfall in Minneapolis and change the look of it forever?
A. To stop it from eroding any further upriver and to keep it in one place
B. To make it into a cool slide for water sports
C. To make it taller and get more power out of it
D. What?? There's a waterfall in Minneapolis!?
Answer: A
The milling industry was in danger of losing their power source if the waterfall kept eroding so they attempted to cover the sandstone with wood at first, but that didn't work very well. Eventually the Army Corps of Engineers came in to help and covered the falls with cement; it took several years but it has lasted a very long time.