Working with Stream Tables

These last few weeks our 8th grade students have been working with a stream table designed to simulate and teach basic river principles, including: how river channels form and change over time and how sediment is transported and deposited within river systems.

The stream table was built with an old wood household door that was no longer being used as the base.  It has the dimensions of 1.91 meters long by .85 meters wide.  There are numerous coats of silicon to prevent the leaking of water, these coats are especially thick near joints (after three years of use, there haven't been any leaks yet).  At any given time there is also 25-30 gallons of water being circulated throughout the system by a submersible pond pump.

The modeling media inside the stream table is manufactered thermoset plastic from Composition Materials Company (http://www.compomat.com/) in Milford, CT.  It is sold by them as 'Stream Table Mix' and consists of various sizes and densities that do an exceptional job of modeling on sediment is transported and deposited in natural river systems.  We use anywhere between 50-80 pounds of plastic within the stream table for student use.

The idea of using a large stream table came from seeing an example created by the folks at Little River Research & Design (http://www.emriver.com/). 

Minnesota Continental Divide Student Map

The state of Minnesota has four major continental divides which are shown on all Minnesota roadmap.  Because of these divides, Minnesota shares it's water with a large part of the North American continent as water flows downhill, based largely on water flowing away from these divides.

Students recently were required to map the location of these divides and other surface water features found within the watershed.  Some of the surface waters students needed to include on their map include major lakes (Mille Lacs, Upper/Lower Red, Winni, Superior, etc) and major rivers (Mississippi, Minnesota, St. Croix, Red, etc.).  An example of a student completed map is posted for reference.

Minnesota's Continental Divides

Water is one of Minnesota's most important natural resources.  Continental divides force water to that falls on one side of them to flow one direction, while water that falls on the other side flows the other direction due to gravity.  The majority of water that falls on Minnesota drains through a series of rivers to the Mississippi River and ultimately, the Gulf of Mexico.

In the southwestern portion of the state, another high area or divide, forces water that falls in that area to drain to the southwest towards the Missouri River.  Of course, the Missouri River ultimately flows into the Mississippi River and then the Gulf of Mexico.  Of course, this particular picture was taken in Minnesota, though it's a continuation of the same divide.  This picture was taken near Carroll, Iowa.

Across the northern portion of the state runs the Laurentian Divide.  Water the falls to the north of this divide flows to the north towards Hudson Bay, in Canada's far north.  Water falling to south of the Laurentian Divide flows either to the Mississippi River or towards Lake Superior.  Water that flows to Lake Superior ultimately flows through the Great Lakes to the Atlantic Ocean.

In places where two continental divides meet you can find triple divide points or triple points.  On of these three way continental divides occurs in Minnesota near Hibbing.  The exact triple divide point is located inside the private property of a taconite mine, so it is not accessible to the public.  Early Native Americans living in the area called this spot "the hill of three waters."

Looking at the picture below (source:  http://commons.wikimedia.org/wiki/File%3ANorthAmerica-WaterDivides.png) you can find several other triple divide points.  One of interest would be the one located at Triple Divide Peak in Glacier National Park.  Water falling on this location flows three directions; west to the Pacific Ocean, north to the Arctic Ocean, and east to the Atlantic Ocean.  This is apparently the only location on the planet where water flows into three separate oceans.

Most might find the pictures of continental divides as rather boring, especially when you compare the Minnesota pictures to the picture of the continental divide located at Loveland Pass in Colorado.  Loveland Pass is located on the Great Divide, this divide separates water that flows in the Pacific Ocean from that that flows in the Atlantic Ocean.  The Great Divide runs across a series of mountain ranges from North America all the way to the Andes in South America.

Our 8th grade students have been using Minnesota roadmaps this week to map out locations of continental divides located in our state.  Using this information, they then map major rivers and lakes and determine how waters flow throughout our state.

Help with Calculating the Mississippi River's Gradient

Take a look at the attached files and use these as a guide or homework check for you assignment that is due soon.

The gradient of a river measures the change in elevation over a certain distance.  All rivers flow downhill due to the force of gravity.  To calculate gradient, you must find the change in elevation between two locations and divide that by the change in distance.
Since we measure elevation in feet and distance in miles, the units for gradient will be feet per mile (ft/mile).

MN River Valley Area - Field Investigation 2011

We just returned to Delano.....24 cameras in the hands of students....I haven't even begun to download all of the pictures taken.  Here's just a few to start, I'll add more later...with descriptions of what all of this means.

Mineral Characteristics Lab

We have just recently begun a new unit that focuses on Minerals.  One reason why they are so important for humans are for there gem or ore qualities.  Gems are minerals that can be used for jewelry.  Ores are the minerals that can be mined for a profit.

Our first lab of the unit was spent looking at different physical properties of minerals and identifying minerals because of these properties.  Using four different sets of minerals, we looked at properties including hardness, cleavage and/or fracture, tenacity and streak.

Mineral Hardness --- a measure of how a mineral resists being scratched.

Cleavage --- the tendency of a mineral to break along smooth, flat planes.

Fracture --- the tendecy of a mineral to break unevenly or irregularly.

Tenacity --- a measure of how a mineral resists acts of destruction like breaking, crushing, bending, etc.

Streak --- the color of a mineral in it's powdered form.

Freezing & Melting Point Lab

The last two weeks we've been working on being able to measure and observe physical properties like density and solubility.  The most recent pysical properties we measured were the freezing point and melting points of napthalene, the active ingredient in moth balls.

Freezing point is the temperature that a liquid becomes a solid, where an object's melting point is the temperature where a solid becomes a liquid.  Students were able to relate this unknown chemicals to the freezing & melting points of water, a substance much more well known.

Solubility Lab

We have just completed a short lab focusing on what factors affect the solubility (the ability of a substance to dissolve in another substance) of copper sulfate.  We tested the following factors in class:  copper sulfate in powder or crystal form, type of solvent (water or ethyl alcohol), temperature of solvent, and amount of solvent. 

Density Lab

This week we've been focusing on the physical property of density.  The density of an object can be calculated after the mass and the volume of that object has been measured.  Density is a measure of how tightly matter is packed into a given volume.  To calculate density, students need to find the mass of an object (in grams) and divide that by the objects volume (in either mL or cubic centimeters).  For reference, objects with densities over 1.0 g/mL will sink in water, which objects with densities less than 1.0 g/mL will float in water.  Objects with higher densities will have a tendency to sink while objects with lower densities will tend to rise.

Density is one of the key concepts of 8th grade Earth Science.  It is an essential to understanding many of our topics later this year, including, but not limited to:  rocks/minerals, weather systems (high/low pressure, land/sea breezes, etc.), planetary research, and plate tectonics.

Contour Lines and Topographical Maps

We've spent the last two days working outside (what a great two days of weather too) learning about contour lines.  Contour lines are lines on a topographical map that connect points of the same elevation.  Using a simple hand level and a six-foot rod that has been measured into one foot increments, students developed ways to create a contour line based on a specific elevation.

First Day of School - Observations

The first day of school is completed.  The goal today was to practice making observations, in particular making those observations to be more in-depth, as opposed to a more simplistic version.  Students worked to use their five senses to notice a particular object.  Questions?  As always, let me know!